Status Assessment of Laysan and Black-Footed Albatrosses, 

North Pacific Ocean, 1923–2005

Scientific Investigations Report 2009-5131

U.S. Department of the Interior

U.S. Geological Survey
Cover: Photograph of Laysan and black-footed albatrosses. 

Photograph taken by Eric VanderWerf, Pacific Rim Conservation. 
Status Assessment of Laysan and 

Black-Footed Albatrosses, 

North Pacific Ocean, 1923–2005

By Javier A. Arata, University of Massachusetts-Amherst, Paul R. Sievert, 

U.S. Geological Survey, and Maura B. Naughton, U.S. Fish and Wildlife Service

Scientific Investigations Report 2009-5131

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

KEN SALAZAR, Secretary

U.S. Geological Survey

Suzette M. Kimball, Acting Director

U.S. Geological Survey, Reston, Virginia: 2009

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Suggested citation:

Arata, J.A., Sievert, P.R., and Naughton, M.B., 2009, Status assessment of Laysan and black-footed albatrosses, North 

Pacific Ocean, 1923–2005: U.S. Geological Survey Scientific Investigations Report 2009-5131, 80 p.
iii

Contents

Executive Summary.......................................................................................................................................1

Introduction.....................................................................................................................................................2

Taxonomy ........................................................................................................................................................4

Legal and Conservation Status....................................................................................................................4

Species’ Descriptions ...................................................................................................................................5

Geographic Distribution................................................................................................................................5

Breeding Colonies.................................................................................................................................5

At-Sea Distribution ..............................................................................................................................5

At Sea: Breeding Albatrosses ...................................................................................................6

At Sea: Non-Breeding Albatrosses ..........................................................................................7

Natural History ...............................................................................................................................................8

Laysan Albatross...................................................................................................................................8

Breeding Cycle.............................................................................................................................8

Nests and Nest Spacing.............................................................................................................8

Breeding Site and Mate Fidelity................................................................................................8

Demography and Limiting Factors ............................................................................................8

Predators.......................................................................................................................................9

Diet and Foraging Behavior .....................................................................................................10

Black-Footed Albatross .....................................................................................................................10

Breeding Cycle...........................................................................................................................10

Nests and Nest Spacing...........................................................................................................10

Breeding Site and Mate Fidelity..............................................................................................11

Demography and Limiting Factors ..........................................................................................11

Predators.....................................................................................................................................11

Diet and Foraging Behavior .....................................................................................................11

Habitat Requirements..................................................................................................................................12

Threats...........................................................................................................................................................12

Fishery Bycatch...................................................................................................................................12

Description of the Fisheries .....................................................................................................12

Bycatch Estimation....................................................................................................................14

Predation..............................................................................................................................................16

Introduced Species ............................................................................................................................16

Habitat Loss and Degradation ..........................................................................................................16

Invasive Plants ...........................................................................................................................16

Urban and Military Development ............................................................................................16

Conflicts with Military Activities ......................................................................................................17
iv

Threats—Continued

Pesticides and Other Contaminants ................................................................................................18

Metals .........................................................................................................................................18

Organochlorine Contaminants.................................................................................................18

Plastics .................................................................................................................................................20

Disease.................................................................................................................................................20

Population Size and Isolation ...........................................................................................................20

Climate Change ...................................................................................................................................21

Monitoring and Management Activities ..................................................................................................21

Monitoring ...........................................................................................................................................21

Breeding Surveys.......................................................................................................................21

Bycatch Monitoring...................................................................................................................22

Management Activities......................................................................................................................22

Protection of Nesting Islands ..................................................................................................22

Habitat and Vegetation Management ....................................................................................22

Predator Management..............................................................................................................23

Fishery Management ................................................................................................................23

Migratory Bird Treaty Act.........................................................................................................23

Population Status and Trends ...................................................................................................................23

Population Analysis Methods...........................................................................................................24

Results for Laysan Albatross ............................................................................................................24

Population Estimates – A Historical Review .........................................................................24

Regression Analysis of Count Data ........................................................................................29

Population Viability Analyses (PVA) of Count Data..............................................................29

Matrix Model Analyses.............................................................................................................32

Results for Black-Footed Albatross.................................................................................................35

Population Estimates – A Historical Review .........................................................................35

Regression Analysis of Count Data ........................................................................................39

Population Viability Analyses (PVA) of Count Data..............................................................39

Matrix Model Analyses.............................................................................................................46

Discussion: Laysan and Black-Footed Albatrosses Population Analyses................................49

Population Viability Analyses...................................................................................................49

Incidental Mortality of Albatrosses ........................................................................................50

Conclusions...................................................................................................................................................51

Acknowledgments.......................................................................................................................................51

References Cited..........................................................................................................................................52

Appendix A: Bycatch Estimation................................................................................................................61

Appendix B. Descriptions and History of the Northwestern Hawaiian Islands.................................73

Appendix C. Detailed Methods for Analysis of Population Trends and Bycatch Impacts...............77

Contents—Continued
v

Figures

Figure 1. Map showing breeding distribution of Laysan and black-footed albatrosses,

North Pacific Ocean ........................................................................ 3

Figure 2. Maps showing kernel density distribution for breeding and non-breeding

black-footed and Laysan albatrosses from satellite (PTT) and geolocator (GLS)

tracking data ................................................................................. 6

Figure 3. Graph showing total estimated number of Laysan albatrosses killed by

commercial fisheries in the North Pacific Ocean, 1951–2005 ........................ 15

Figure 4. Graph showing total estimated number of black-footed albatrosses killed by

commercial fisheries in the North Pacific Ocean, 1951–2005 ........................ 15

Figure 5. Graphs showing number of Laysan albatross breeding pairs at colonies from

the 1920s until 2005 ........................................................................ 24

Figure 6. Graphs showing number of breeding pairs of Laysan albatross on Midway

Atoll, Laysan Island, and French Frigate Shoals, 1958–2005 ........................... 27

Figure 7. Graphs showing observed growth rate distribution (Robs) for the Laysan

albatross breeding population, Laysan Island .......................................... 29

Figure 8. Graphs showing population projection (A, n = 30) and cumulative probability

(B) that a given rate of population change is reached over 60 years using the

exponential model and re-analysis of transect data for Laysan albatross,

Laysan Island................................................................................. 31

Figure 9. Graphs showing observed growth rate distribution (Robs) for the Laysan

albatross breeding population, French Frigate Shoals ................................. 31

Figure 10. Graphs showing projection (A, n = 30) and cumulative probability (B) that a

given rate of population change is reached over 60 years using the

exponential model for Laysan albatross, French Frigate Shoals ..................... 33

Figure 11. Graph showing World Laysan albatross breeding population trend as derived

from estimates for each island ............................................................ 33

Figure 12. Graphs showing potential growth rate (A) and net growth (B) for the Laysan

albatross .................................................................................... 35

Figure 13. Graphs showing number of black-footed albatross breeding pairs at colonies

from the 1920s until 2005 .................................................................. 37

Figure 14. Graphs showing number of breeding pairs of black-footed albatross on

Midway, Laysan, and French Frigate Shoals from the 1950s to 2005. ............... 38

Figure 15. Graphs showing observed growth rate distribution (Robs) for the black-footed

albatross breeding population, Midway Atoll .......................................... 40

Figure 16. Graphs showing population projection (A, n = 30) and cumulative probability

(B) that a given rate of population change is reached over 60 years using the

exponential model for black-footed albatross, Midway Atoll ........................ 40

Figure 17. Graph showing population estimates for black-footed albatross, Laysan Island. ... 41

Figure 18. Graphs showing observed growth rate distribution (Robs) for the black-footed

albatross breeding population, Laysan Island .......................................... 44

Figure 19. Graphs showing population projection (A, n = 30) and cumulative probability

(B) that a given rate of population change is reached over 60 years using the

exponential model and re-analyzed transect data for black-footed albatross,

Laysan Island................................................................................. 44
vi

Figure 20. Graphs showing observed growth rated distribution (Robs) for the 

black-footed albatross breeding population on all of French Frigate 

Shoals (Robs-FFS) and Tern Island (Robs-Tern) only.................................... 45

Figure 21. Graphs showing population projection (A, n = 30) and cumulative 

probability (B) that a given rate of population change is reached 

over 60 years using the exponential model for black-footed albatross, 

French Frigate Shoals ..................................................................... 45

Figure 22. Graph showing World black-footed albatross breeding population 

trend, as derived from estimations at each island .................................... 46

Figure 23. Graph showing Potential Biological Removal estimate using R/4, R/2, 

and R, and initial population sizes of black-footed albatross as obtained 

from each estimated trend for 2004 ...................................................... 48

Figure 24. Graph showing species and islands comparison of the population growth 

rate, â, and the environmental variance, σenv  , estimated with the exponential 

model (mean and 95-percent CI) ......................................................... 49

Figures—Continued

Tables

Table 1. Data sources used in bycatch estimations for Laysan (LAAL) and black-footed

(BFAL) albatrosses ........................................................................ 14

Table 2. Estimated number of Laysan (LAAL) and black-footed (BFAL) albatrosses

killed on Midway Atoll in control programs, experiments, and collisions with

antennas, and aircraft and road collisions, 1956–67 .................................... 17

Table 3. Mean and range of organochlorine concentrations in the subcutaneous fat of

adult Laysan albatrosses and whole eggs, Midway Atoll .............................. 19

Table 4. Mean and range of organochlorine concentrations in subcutaneous fat of

adult black-footed albatrosses and whole eggs, Midway Atoll........................ 19

Table 5. Estimates of the number of Laysan albatross breeding pairs by colony and

hatch year at all extant colonies ......................................................... 26

Table 6. Results of linear regression analyses of trends in Laysan and black-footed

albatross populations at French Frigate Shoals, Laysan Island, and Midway

Atoll combined .............................................................................. 29

Table 7. Parameter estimation for exponential and logistic R-function models fitted to

Laysan albatross Robs data, Laysan Island ............................................. 30

Table 8. Parameter estimation for exponential and logistic R-function models fitted to

Laysan albatross Robs data after re-analysis of transect data, Laysan Island ...... 30

Table 9. Parameter estimation for exponential and logistic R-function models fitted to

Laysan albatross Robs data, French Frigate Shoals .................................... 32

Table 10. Parameter estimates [median (95-percent CI)] for the Laysan albatross

population-projection matrix under different model structures........................ 34

Table 11. Demographic parameter estimates [mean ± 1 SD (range)] available for the

Laysan albatross ........................................................................... 36

Table 12. Estimates of the number of black-footed albatross breeding pairs by colony

and hatch year .............................................................................. 37

Table 13. Parameter estimation for exponential and logistic R-function models fitted to

black-footed albatross Robs data, Midway Atoll ....................................... 42
vii

Multiply By To obtain

Length

centimeter (cm) 0.3937 inch (in.)

millimeter (mm) 0.03937 inch (in.)

meter (m) 3.281 foot (ft) 

kilometer (km) 0.6214 mile (mi)

kilometer (km) 0.5400 mile, nautical (nmi) 

meter (m) 1.094 yard (yd) 

Area

square meter (m2

) 0.0002471 acre 

hectare (ha) 2.471 acre

square kilometer (km2

) 247.1 acre

square centimeter (cm2

) 0.001076 square foot (ft2)

square meter (m2

) 10.76 square foot (ft2) 

square centimeter (cm2

) 0.1550 square inch (ft2) 

square kilometer (km2

) 0.3861 square mile (mi2)

Volume

cubic meter (m3

) 6.290 barrel (petroleum, 1 barrel = 42 gal)

cubic meter (m3

) 264.2 gallon (gal) 

cubic centimeter (cm3

) 0.06102 cubic inch (in3) 

cubic decimeter (dm3

) 61.02 cubic inch (in3) 

cubic meter (m3

) 35.31 cubic foot (ft3)

cubic meter (m3

) 1.308 cubic yard (yd3) 

cubic kilometer (km3

) 0.2399 cubic mile (mi3) 

Mass

gram (g) 0.03527 ounce (oz)

kilogram (g) 2.20462 pound (lb)

Conversion Factors and Datums

Conversion Factors

Table 14. Parameter estimation for exponential and logistic R-function models 

fitted to black-footed albatross Robs data after re-analysis of transect 

samples, Laysan Island ..................................................................... 42

Table 15. Parameter estimation for exponential and logistic R-function models 

fitted to black-footed albatross Robs data derived from direct nest counts, 

Laysan Island................................................................................. 43

Table 16. Parameter estimation for exponential and logistic R-function models fitted

to black-footed albatross Robs data, French Frigate Shoals........................... 43

Table 17. Demographic parameter estimates [mean ± 1 SD (range)] available for the

black–footed albatross .................................................................. 47

Table 18. Parameter estimates [median (95-percent CI)] for the black–footed

albatross population–projection matrix................................................... 48

Tables—Continued
viii

Conversion Factors and Datums—Continued

Temperature in degrees Celsius (°C) may be converted to degrees Fahrenheit (°F) as follows:

°F=(1.8×°C)+32.

Temperature in degrees Fahrenheit (°F) may be converted to degrees Celsius (°C) as follows:

°C=(°F-32)/1.8.

Datums

Vertical coordinate information is referenced to the North American Vertical Datum of 1988 

(NAVD 88).

Horizontal coordinate information is referenced to the North American Datum of 1983 (NAD 83).

Altitude, as used in this report, refers to distance above the vertical datum.

Abbreviations and Acronyms

ACAP Agreement on the Conservation of Albatrosses and Petrels

AICc Akaike’s Information Criterion corrected

AOU American Ornithologist’s Union

asl above sea level

BCME British Columbia Ministry of Environment

BPUE Birds per Unit Effort

BFAL Black-Footed Albatross

BSAI Bering Sea and Aleutian Islands

CI Confidence Interval

CITES Convention on International Trade in Endangered Species 

COSEWIC Committee on the Status of Endangered Wildlife in Canada

CPD Cumulative Probability Distribution

CV Coefficient of Variation

DDE 1,1-dichloro-2,2’-bis-p-chlorophenyl-ethylene

DDT Dichlorodiphenyltrichloroethanes

EEZ Exclusive Economic Zone

ESA Endangered Species Act

FFS French Frigate Shoals

GLEMEDS Great Lakes Embryo Mortality Edema and Deformities Syndrome

GOA Gulf of Alaska

HI Hazard Index

HI Hawai`i

ICEG Island Conservation and Ecology Group

IPHC International Pacific Halibut Commission

IUCN World Conservation Union

JPLM Japanese Large-Mesh Fishery

JPLS Japanese Land-based Salmon Fishery

JPMS Japanese Mothership Salmon Fishery
ix

JPSQ Japanese Squid Fishery

KOSQ Korean Squid Fishery

LAAL Laysan Albatross

LORAN Long Range Aids to Navigation 

LRT and LR Likelihood Ratio Test

MBTA Migratory Bird Treaty Act

MMPA Marine Mammal Protection Act

NMFS National Marine Fisheries Service

NPAWG North Pacific Albatross Working Group

NOAEL No Observable Adverse Effect Level

NOM Norma Oficial Mexicana

NWHI Northwestern Hawaiian Islands

NWR National Wildlife Refuge

OFP Ocean Fisheries Program

PBR Potential Biological Removal

PCB Polychlorinated biphenyls

PCDD Polychlorinated dibenzodioxins

PVA Population Viability Analysis

RFMO Regional Fishery Management Organization

SD Standard Deviation

SEMARNAT Secretaría de Medio Ambiente y Recursos Naturales

SWR Southwest Region

TCDD Tetrachlorodibenzo-piodoxin

TEQ Toxic equivalent

TWDF Taiwanese Squid Fishery

UN United Nations

U.S. United States

USFWS United States Fish and Wildlife Service

USGS United States Geological Survey

WWII World War II

Abbreviations and Acronyms—Continued
x

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Status Assessment of Laysan and Black-Footed 

Albatrosses, North Pacific Ocean, 1923–2005

By Javier A. Arata1, Paul R. Sievert2, and Maura B. Naughton3

Executive Summary

Over the past century, Laysan (Phoebastria immutabilis) 

and black-footed (Phoebastria nigripes) albatrosses have 

been subjected to high rates of mortality and disturbance at 

the breeding colonies and at sea. Populations were greatly 

reduced and many colonies were extirpated around the turn 

of the 20th century as a result of feather hunting. Populations 

were recovering when military occupation of several breeding 

islands during World War II led to new population declines 

at these islands and additional colony extirpations. At sea, 

thousands of Laysan and black-footed albatrosses were killed 

each year in high-seas driftnet fisheries, especially from 

1978 until the fisheries were banned in 1992. Through the 

1990s, there was a growing awareness of the large numbers of 

albatrosses that were being killed in longline fisheries. During 

the 1990s, other anthropogenic factors, such as predation by 

non-native mammals and exposure to contaminants, also were 

documented to reduce productivity or increase mortality. 

In response to the growing concerns over the impacts 

of these threats on albatross populations, the U.S. Fish 

and Wildlife Service contracted with the U.S. Geological 

Survey to conduct an assessment of Laysan and black-footed 

albatross populations. This assessment includes a review of 

the taxonomy, legal status, geographic distribution, natural 

history, habitat requirements, threats, and monitoring and 

management activities for these two species. The second part 

of the assessment is an analysis of population status and trends 

from 1923 to 2005.

Laysan and black-footed albatrosses forage throughout 

the North Pacific Ocean and nest on tropical and sub-tropical 

oceanic islands from Mexico to Japan. As of 2005, 21 islands 

support breeding colonies of one or both species. The core 

breeding range is the Hawaiian Islands, where greater than 

99 percent of the World’s Laysan albatrosses and greater than 

95 percent of the black-footed albatrosses nest on the small 

islands and atolls of the Northwestern Hawaiian Islands. These 

islands are all protected as part of the Papahānaumokuākea 

Marine National Monument.

Albatrosses are long-lived seabirds with deferred 

maturity, low fecundity, and high rates of adult survival. 

Their life history characteristics make populations especially 

vulnerable, to small increases in adult mortality. The 

primary threats to Laysan and black-footed albatrosses 

include interactions with commercial fisheries, predation 

by introduced mammals, reduced reproductive output due 

to contaminants, nesting habitat loss and degradation due to 

human development and invasive plant species, and potential 

loss and degradation of habitat due to climate change and 

sea-level rise. Incidental mortality (bycatch) in commercial 

fisheries is the greatest anthropogenic source of mortality 

(post-fledging) for both species. We found that longline 

fishing effort prior to the 1980s was greater than previously 

estimated and a very significant source of mortality.

Regulations to minimize and monitor albatross mortality 

have been enacted in most U.S. and Canadian longline 

fisheries, but monitoring of bycatch rates and regulations 

to minimize seabird mortality are extremely limited in the 

much larger multinational longline fleets. Management 

to address threats at the breeding colonies is ongoing and 

includes eradication or control of non-native species, habitat 

management, and abatement programs to reduce impacts 

of contaminants. Effective long-term conservation and 

management of the Laysan and black-footed albatrosses 

require management and monitoring at the breeding colonies 

and at sea and continued assessment of population status and 

trends.

1 University of Massachusetts, Department of Natural Resources 

Conservation, Amherst, MA.

2

U.S. Geological Survey, Massachusetts Cooperative Fish and Wildlife 

Research Unit, University of Massachusetts, Amherst, MA.

3

U.S. Fish and Wildlife Service, Migratory Birds and Habitat Programs, 

Portland, OR.
2 Status Assessment of Laysan and Black-Footed Albatrosses, North Pacific Ocean, 1923–2005

We evaluated the status and trends of Laysan and 

black-footed albatross populations using linear regression, 

population viability analysis (PVA), and age-structured matrix 

models. Analyses were predominantly based on nest-count 

data gathered at French Frigate Shoals, Laysan Island, and 

Midway Atoll. At these three colonies, nest counts were 

greater than 75 percent of the World’s population of blackfooted albatrosses and greater than 90 percent of the World’s 

population of Laysan albatrosses. The first quantitative 

estimates for most colonies were made in 1923, after the era 

of feather hunting, when populations were at their lowest 

levels. Another comprehensive survey of Hawaiian colonies 

was conducted between 1956 and 1958, after which colony 

counts were irregular until the U.S. Fish and Wildlife Service 

(USFWS) began standardized surveys of French Frigate 

Shoals in 1980, and Laysan Island and Midway Atoll in 

1992. Regression analysis was used to evaluate linear trends 

in populations from 1923 to 2005, 1957 to 2005, and 1992 

to 2005. PVA was conducted by fitting stochastic, discretetime, logistic, and exponential models to observed data and 

then making population projections 60 years (about three 

generations) into the future. Age-structured population models, 

based on a matrix modeling framework, were used to evaluate 

the effect of fishery bycatch on populations. Estimates of 

albatross bycatch were either obtained by projecting measured 

rates for U.S. fisheries to International fleets or by using 

published values.

The Laysan albatross population increased from an 

estimated 18,000 pairs in 1923 to 590,000 pairs in 2005. The 

large population increase during the past 83 years is likely 

a response to the end of persecution by feather hunters, 

decrease in conflicts with military activities, and an increase 

in nesting areas at some colonies. Analysis of linear trends in 

the population showed a positive change over 1923 to 2005 

and 1957 to 2005 and a stable size from 1992 to 2005. PVA 

results for the Laysan albatross colony on French Frigate 

Shoals indicate that this colony is currently stable, but there 

is a 28-percent probability of the population decreasing by 

24 percent over the next 60 years. PVA results for the Laysan 

Island colony indicate that the colony is most likely to increase 

in size over the next 60 years, but there also is a 45-percent 

probability of the colony decreasing in size. PVA was not 

conducted for Midway Atoll due to the small sample size. 

Matrix modeling results indicate that the Laysan albatross 

population, summed across all three colonies (Midway 

Atoll, Laysan Island, and French Frigate Shoals), increased 

6.7 percent per year from 1992 to 2005, and the estimated 

bycatch of 2,500 birds per year is less than the estimated 

Potential Biological Removal (PBR—the maximum number 

of mortalities, not including natural deaths, while maintaining 

an optimum sustainable population).

The black-footed albatross population increased from 

an estimated 18,000 pairs in 1923 to 61,000 pairs in 2005. 

As with Laysan albatrosses, the increase in the black-footed 

albatross population over the past 83 years probably is 

in response to the end of persecution at nesting colonies. 

Analysis of linear trends in population size showed a 

positive change from 1923 to 2005, no change from 1957 

to 2005, and no change from 1998 to 2005. PVA results for 

the black-footed albatross colony on French Frigate Shoals 

indicate that this colony has a 50-percent probability of 

increasing by 74 percent in the next 60 years, but it also 

has a 35-percent probability of significantly decreasing. 

PVA results for the Laysan Island colony indicate that the 

population is most likely to increase by 54.7 percent over 

the next 60 years, but also has a 35-percent probability of 

significantly decreasing. PVA results for the Midway Atoll 

colony indicate that it is most likely to increase by 36 percent 

over the next 60 years, and has a 23-percent probability 

of decreasing. Matrix modeling results indicate that the 

black-footed albatross population, summed across all three 

colonies, is stable, or slightly increasing, with a population 

growth rate of 0.3 percent per year. The 2005 estimate of 

bycatch is 5,228 birds per year, but if this value is doubled, 

a safeguard for underestimating bycatch, it approaches the 

PBR of 11,980 birds per year, although the upper 95-percent 

confidence limit (17,486) exceeds the PBR. 

Our knowledge of interactions of Laysan and blackfooted albatrosses with fishing operations is imperfect, partly 

because of the difficulty of obtaining reliable bycatch data 

from all fleets. Results from the matrix modeling indicate that 

fishery bycatch is not significantly affecting the size of the 

Laysan albatross population, but may be causing a decrease in 

black-footed albatross populations.

Introduction

Laysan and black-footed albatrosses breed on oceanic 

islands in the subtropical and tropical Pacific Ocean, between 

14oN and 31oN latitude, from Mexico to the East China Sea 

(Harrison, 1990; Whittow, 1993a and 1993b, fig. 1). The 

majority of birds nest on the low islands and atolls of the 

Northwestern Hawaiian Islands, and their foraging habitat 

includes most of the North Pacific Ocean (Rice and Kenyon, 

1962a; Tickell, 2000). During the last century, these species 

have been subject to high rates of mortality and disturbance at 

both the breeding colonies and foraging grounds (Cousins and 

Cooper, 2000; Tickell, 2000; Lewison and Crowder, 2003). 

Populations were greatly reduced, and Laysan and blackfooted albatrosses were extirpated from many breeding islands 

by feather hunters during the late 19th and early 20th centuries 

(Rice and Kenyon, 1962a; Spennemann, 1998; Tickell, 2000). 
Introduction 3

tac_08_9354_0255_Albatrosses_Fig01

See inset below

156°W 160°W 164°W 168°W 172°W 176°W 180°

28°N26°N24°N22°N20°N

0 100 200 300 MILES0 100 200 300 400 500 KILOMETERS

Midway Pearl &

Hermes Reef

Lisianski

Laysan

French Frigate Shoals

Necker Nihoa

Kaula

Ni`ihau

Lehua

Kaua`i

O`ahu

Kure

N o r t h w e s t e r n I s l a n d s M a i n I s l a n d s Hawaiian Islands

Hawai`i

Maui

Kaho`olawe

Lāna`i

Moloka`i

GardnerPinnacles Maro

Reef

WakeAtoll

MinamiTorishima

Kazan

Retto

Torishima

Isla de Guadalupe

Clarion

San

Benedicto

Izu Shoto

Alijos Rocks

R U S S I A

C H I N A

C A N A D A

A U S T R A L I A

I N D O N E S I A

M E X I C O

N KOREA

S KOREA

Equator

TAIWAN

U N I T E D

S T A T E S

P H I L I P P I N E S

PAPUA

NEW GUINEA

H a w a i i a n I s l a n d s

J A

P

A

N

Ogasawara

(Bonin Is.) Senkaku Retto

. sI anair a M

Marshall IslandsJohnston Atoll Islas Revillagigedo

P A C I F I C

O C E A N

(Phoebastria immutabilis and Phoebastria nigripes)

EXPLANATION

Laysan:

BreedingExtirpated

BreedingExtirpated

Black-footed: Both:

BreedingExtirpated

Breeding Distribution of

Laysan and Black-Footed Albatross

120°E

50°N30°N10°N

10°S

140°E 160°E 180° 160°W 140°W 120°W 100°W

120°E 140°E 160°E 180° 160°W 140°W

0°

50°N100°W30°N10°N0°10°S

120°W

0 2,000 MILES0 1,000

1,000

2,000 KILOMETERS

Map from U.S. Fish and Wildlife Service, Pacific Region, ES/GIS, September 2008. Projection: Word Robinson, with a central median of 180 degrees. Datum is Word Geodetic System, 1984Photo credit: Maura Naughton

Figure 1. Breeding distribution of Laysan and black-footed albatrosses, North Pacific Ocean. 
4 Status Assessment of Laysan and Black-Footed Albatrosses, North Pacific Ocean, 1923–2005

Designation of the Hawaiian Islands Bird Reservation (later 

renamed the Hawaiian Islands National Wildlife Refuge) in 

1909 provided protection to breeding colonies in the core 

breeding range. Human occupation and military activities 

at several breeding islands, during and subsequent to World 

War II, degraded nesting habitat and reduced the breeding 

populations at these islands, including the extirpation of some 

colonies (Fisher and Baldwin, 1946; Rice and Kenyon, 1962a). 

Introduced mammalian predators have been removed from all 

the larger colony sites in the Northwestern Hawaiian Islands, 

but they remain a threat to smaller colonies and may be an 

impediment to recolonization of historical nesting sites. At sea, 

albatrosses have been subjected to mortality by commercial 

fisheries (Johnson and others, 1993; Cousins, 2001; Lewison 

and Crowder, 2003) and exposure to contaminants (Ludwig 

and others, 1998; Guruge and others, 2001a and 2001b; 

Finkelstein and others, 2006).

The U.S. Fish and Wildlife Service contracted with the 

U.S. Geological Survey to conduct a status assessment of 

Laysan and black-footed albatrosses due to concerns over 

the status of the populations and the impacts of threats. The 

assessment includes a review of the taxonomy, legal status, 

natural history, and population status and trends of these two 

species. Population trends were based on data collected at 

French Frigate Shoals, Laysan Island, and Midway Atoll; 

sites where 75 percent of the World’s population of blackfooted albatross and 90 percent of the World’s Laysan 

albatrosses nest. Population changes were analyzed using 

linear regression, population viability analysis (PVA) and agestructured population models.

Taxonomy

Molecular analyses based on the mitochondrial 

cytochrome-b gene identified a strong phylogenetic 

relationship among all North Pacific albatrosses, supporting 

the former designation of Phoebastria (Reichenbach, 1852) 

for this group (Nunn and others, 1996; Robertson and Nunn, 

1998), a classification that has been adopted by the American 

Ornithologists’ Union (1997).

The current taxonomy for the Laysan albatross is 

Phoebastria immutabilis, Order Procellariiformes, Family 

Diomedeidae (American Ornithologists’ Union, 1998). No 

subspecies are recognized (Robertson and Nunn, 1998; 

BirdLife International, 2004a).

The current taxonomy for the black-footed albatross 

is Phoebastria nigripes, Order Procellariiformes, Family 

Diomedeidae (American Ornithologists’ Union, 1998). There 

are no recognized subspecies (Robertson and Nunn, 1998; 

BirdLife International, 2004b), although a recent study based 

on the mitochondrial cytochrome-b gene identified significant 

genetic differentiation between Hawaiian and Japanese 

populations of black-footed albatrosses (Walsh and Edwards, 

2005).

Legal and Conservation Status

In the United States, Canada, Japan, Russia, and China, 

migratory birds, including albatrosses, are protected by 

domestic legislation that implements migratory bird treaties 

(summarized in Harrison and others, 1992) including the 

Migratory Bird Treaty Act (United States), Migratory Bird 

Convention Act (Canada), Wildlife Protection and Hunting 

Law (Japan), On the Protection and Use of Wild Animals 

(Russia), and Wildlife Protection Law (China).

Additional protective designations include:

United States

• A petition to list black-footed albatross under the 

Endangered Species Act (ESA) was submitted to 

the USFWS by Earth Justice and is currently under 

review to determine if listing is warranted. Blackfooted albatross is listed as a Bird of Conservation 

Concern at national and regional levels and in Bird 

Conservation Regions 5, 32, 67, and 68 (U.S. Fish and 

Wildlife Service, 2002). Laysan albatross is listed in 

Bird Conservation Regions 5, 67, and 68 (U.S. Fish 

and Wildlife Service, 2002). Black-footed albatross is 

listed as threatened by the State of Hawai`i (Mitchell 

and others, 2005).

Mexico

• Both species are listed as ‘Amenazada’ (Threatened) 

under the List of Species at Risk, Annex 2, of the 

Norma Oficial Mexicana NOM-059-ECOL-2001 

(March 6, 2002; http://www.ine.gob.mx/ueajei/

publicaciones/normas/rec_nat/no_059.html).

Canada

• Black-footed albatross was assessed nationally as a 

species of Special Concern by the Committee on the 

Status of Endangered Wildlife in Canada (2007). The 

Federal government is evaluating whether the species 

should receive legal listing under the Species at Risk 

Act.

• Provincially, black-footed albatross is considered 

secure and at no risk of extinction in British Columbia 

(that is, on BC’s Yellow-list), and Laysan albatrosses 

are considered of Special Concern (that is, on BC’s 

Blue-list; British Columbia Ministry of Environment, 

2007).
Geographic Distribution 5

International

• The International Union for the Conservation of Nature 

and Natural Resources (IUCN) listed black-footed 

albatross as Endangered in 2003 (International Union 

for the Conservation of Nature and Natural Resources, 

2004) based on a projected decrease of greater than 

60 percent over the next three generations (56 years). 

The stated reason for this projected decrease was 

rate of incidental mortality in longline fisheries in 

North Pacific Ocean (International Union for the 

Conservation of Nature and Natural Resources, 2004; 

based on Lewison and Crowder, 2003).

• The IUCN listed Laysan albatross as Vulnerable in 

2003 (International Union for the Conservation of 

Nature and Natural Resources, 2004) based on a 

projected decrease of greater than 30 percent over 

three generations (84 years). The stated reason for 

this projected decrease also was attributed to effects 

of longline fishing in the North Pacific Ocean, a 

threat that is ongoing (International Union for the 

Conservation of Nature and Natural Resources, 2004). 

• Both species are listed in Appendix II of the 

Convention on Migratory Species (the Bonn 

Convention). Appendix II species “have an 

unfavourable conservation status or would benefit 

significantly from International co-operation organized 

by tailored agreements.”

Species’ Descriptions

The Laysan albatross is a medium-sized albatross, 

weighing approximately 3.2 kg, with males weighing about 

10 percent more than females. They are 79–81 cm in length 

with a 195–203 cm wingspan (Harrison, 1985). The bill 

is pinkish-orange with a grey tip, and the feet are flesh to 

pink in color. The upper wings, mantle, back, upper rump, 

and tail are dark sooty brown. The head, lower rump, and 

underparts are white. The eyes have black shading and a dark 

iris. The sides of the head are washed with grey. The blackand-white underwing pattern varies among individuals, with 

wing margins having a narrow, black band and underwing 

coverts varying in amount of black. Juveniles have a similar 

appearance to adults, but have a greyer bill and less grey on 

the face.

The black-footed albatross is a medium-sized, darkbrown albatross, 68–74 cm in length, with a wingspan of 

193–213 cm (Harrison, 1985). All ages have a blackish bill, 

legs, and feet. Adults are dusky brown, with white under the 

eye, a white band of feathers encircling the base of the bill, 

and white feathers over the base of the tail and undertailcoverts. Fledglings are uniformly dark brown and acquire the 

white ring at the base of the bill and around the tail with age 

(Hyrenbach, 2002).

Geographic Distribution

Breeding Colonies

The Laysan and black-footed albatrosses are openocean species, coming to land exclusively to breed. The core 

breeding range, supporting more than 99 and 95 percent of the 

breeding populations of Laysan and black-footed albatrosses, 

respectively, are the low, sandy islands of the Northwestern 

Hawaiian Islands (NWHI, fig. 1). The NWHI are the small 

islands and atolls located northwest of the islands of the main 

Hawaiian Islands. These include Kure and Midway atolls, 

Pearl and Hermes Reef, Lisianski, Laysan, Gardner Pinnacles, 

French Frigate Shoals, Necker, and Nihoa Islands. On the 

main Hawaiian Islands, black-footed albatrosses nest on the 

westernmost islands of Ka`ula and Lehua (VanderWerf and 

others, 2007). Laysan albatrosses nest more extensively on the 

main Hawaiian Islands on Ka`ula, Lehua, Ni`ihau, Kaua`i, and 

O`ahu (Harrison, 1990; VanderWerf and others, 2007). A few 

pairs of each species recently recolonized Wake Island, a U.S. 

territory in the central Pacific, but only Laysan albatrosses 

have successfully fledged a chick from this location (Rauzon 

and others, 2008).

Laysan albatrosses also breed on Mukojima in Japan 

(Ogasawara Islands or Bonin Islands; Hasegawa, 1984) 

and islands off Mexico on Guadalupe Island, Revillagigedo 

Islands (Clarión and San Benedicto islands), and Alijos Rocks 

(Pitman, 1985; Pitman and others, 2004). In Japan, blackfooted albatrosses breed on Torishima of the Izu Islands; 

several islands in the Mukojima and Hahajima rettos of the 

Ogasawara Islands; and on Kita-kojima and Minami-kojima 

in the Senkaku Retto (Hasegawa, 1984; Tickell, 2000; 

T. Deguchi, Yamashina Institute for Ornithology, written 

commun., 2006; N. Nakamura, Yamashina Institute for 

Ornithology, written commun., 2008). Individual pairs of 

black-footed albatrosses successfully nested on Guadalupe 

Island in 1998 and San Benedicto in 2000 (Pitman and 

Ballance, 2002). 

Whereas the breeding range has expanded with these new 

colonies in Mexico (Dunlop, 1988; Pitman and others, 2004), 

several historically large colonies extirpated by feather hunters 

in the central and western Pacific have not reestablished (Rice 

and Kenyon, 1962a; Tickell, 2000). 

At-Sea Distribution 

The foraging range for albatrosses changes with the phase 

of the breeding cycle. Foraging distribution has been studied 

using band recoveries, shipboard surveys and, more recently, 

satellite telemetry and geolocational loggers. BirdLife 

International provided maps from their Tracking Ocean 

Wanderers Database to illustrate the breeding and 

non-breeding distribution of these two species (fig. 2). 
6 Status Assessment of Laysan and Black-Footed Albatrosses, North Pacific Ocean, 1923–2005

A detailed description of the methods and maps can be found 

in BirdLife International (2004c). The utilization distributions 

shown in these maps represent areas used by tracked birds; 

areas of low or no density do not imply an absence of birds. 

Areas close to deployment locations, particularly at-sea 

deployments where bird density does not approach that of the 

colonies, could show a higher use bias because the tracks are 

not independent samples.

At Sea: Breeding Albatrosses

Laysan Albatross.—Foraging trips of breeding Laysan 

albatrosses tagged at French Frigate Shoals occur in tropical 

waters (greater than 20°C), as well as colder subarctic and 

tac_08_9354_0255_Albatrosses_Fig02

120°E 140°E 160°E 180° 160°W 140°W 120°W

50°N

70°N

30°N

10°N

120°E 140°E 160°E 180° 160°W 140°W 120°W

50°N

70°N

30°N

10°N

140°E 160°E 180° 160°W 140°W 120°W

50°N

70°N

30°N

10°N

140°E 160°E 180° 160°W 140°W 120°W

50°N

70°N

30°N

10°N

EXPLANATION

At-sea deployment

Breeding sites

Tracked

Unknown

Distribution, in percent

50

75

95

Range

0

0

3,000 MILES

5,000 KILOMETERS

Projection: Plate Caree, Geographic

Coordinate System. Datum: World

Geodetic System, 1984

A. Black-footed albatross breeding B. Black-footed albatross nonbreeding

C. Laysan albatross breeding D. Laysan albatross nonbreeding 

(Source: Maps produced by BirdLife International, the BirdLife Global 

Procellariiform Tracking Database using data from Scott A. Shaffer, 

Michelle Kappes, Yann Tremblay, Dan P. Costa, Bill Henry, and 

Don A. Croll (University of California, Santa Cruz); Dave J. Anderson 

and Jill Awkerman (Wake Forest University); Michelle Hester and 

David Hyrenbach (Oikonos – Ecosystem Knowledge and Duke University); 

Rob Suryan and Karen Fischer (Oregon State University); and Greg Balogh 

(U.S. Fish and Wildlife Service).

Figure 2. Kernel density distribution for breeding and non-breeding black-footed and Laysan albatrosses from satellite (PTT) and 

geolocator (GLS) tracking data.

North Pacific Transition Domain waters north of the Hawaiian 

breeding colonies (Hyrenbach and others, 2002; BirdLife 

International, 2004c). Adult foraging trips ranged from 10 to 

32 days during incubation to 1–3 days during chick brooding 

(BirdLife International, 2004c). Hyrenbach and others (2002) 

reported adults brooding chicks made short trips to tropical 

and subtropical waters (greater than 18°C) north of the colony, 

with trips having a median duration of 3 days and a maximum 

distance of 510 km. During the post-guard period, breeding 

adults increased the median duration and maximum range of 

their trips (14.5 days; 2,675 km), mixing short (1–4 days) with 

long (12–29 days) trips north of the colony, over transitional 

(12°–15°C) and subarctic waters (less than 10°C) of the Gulf 

of Alaska and the Aleutian Islands (Hyrenbach and others, 
Geographic Distribution 7

2002). Gender differences were not observed. During 1999, a 

year with high breeding failure, adults that lost chicks flew to 

the Kuroshio-Oyashio Current (30°–45°N and 140°–160°E) 

east of Japan (Fernández and others, 2001). Laysan albatrosses 

generally travel farther north to cool waters along the northern 

edge of the transition zone and farther west of the colony than 

black-footed albatrosses (Gould and others, 1998; S. Shaffer, 

University of California, Santa Cruz, written commun., 2006).

Tracking data of Laysan albatrosses breeding on 

Guadalupe Island, Mexico, show distinctly different foraging 

distributions from birds breeding in Hawai`i (BirdLife 

International, 2004c). Mexican birds primarily remained 

within the California Current System south of 45°N, showing 

little overlap with the at-sea distribution of Laysan albatrosses 

from French Frigate Shoals (BirdLife International, 2004c). 

Black-Footed Albatross.—Breeding adults from Tern 

Island, French Frigate Shoals made both short and long trips. 

During incubation, foraging trips ranged from 10 to 32 days 

(BirdLife International, 2004c). Short trips, having a median 

duration of 2 days and a maximum distance of 303 km, were 

made into tropical waters (greater than 20°C) north of Tern 

Island during brooding and the post-guard periods (Hyrenbach 

and others, 2002, 2006). Long trips, having a median length of 

9 days and a maximum range of 1,174 km, were interspersed 

with short trips during the post-guard period. Long trips 

extended northeast of the colony to the continental shelf off 

western North America from British Columbia to California. 

Roundtrips were a minimum of 9,000 km and lasted at least 

15 days. During a year of low breeding success (1998–99), 

foraging trips during brooding were longer and primarily 

directed to waters distant from North America (Fernández and 

others, 2001). 

At Sea: Non-Breeding Albatrosses

Laysan Albatross.—The western portion of the North 

Pacific Ocean is used to a greater extent by Laysan than 

black-footed albatrosses (fig. 2). Band recovery data indicate 

that young Laysan albatrosses (less than 2 years old) primarily 

are observed off eastern Japan, along the convergence of the 

Kuroshio-Oyashio currents. As they get older, birds gradually 

shift their range east-northeast (Fisher and Fisher, 1972; 

Robbins and Rice, 1974). During summer (non-breeding 

season), adult Laysan albatrosses primarily are observed 

around the Aleutian Islands and the western Gulf of Alaska 

(Robbins and Rice, 1974; McDermond and Morgan, 1993; 

Melvin and others, 2004). Despite the high survey effort, 

few Laysan albatrosses have been observed in the California 

Current System (Miller, 1940; Thompson, 1951; Fisher and 

Fisher, 1972; Briggs and others, 1987; Briggs and others, 

1992). Sightings off southern California since the mid-1980s 

are likely due to northern movement of Guadalupe birds 

(Hyrenbach, 2001). Laysan albatrosses generally are observed 

over, and seaward of, the continental slope over areas of 

strong, persistent upwelling, and along the boundaries of 

different water masses (McDermond and Morgan, 1993), 

such as the North Pacific Subtropical Convergence (Wahl 

and others, 1989). During post-breeding dispersal, Laysan 

albatrosses from Hawai`i move into the northern and western 

Pacific, whereas birds from the Mexican colonies remain in 

the eastern Pacific (S. Shaffer, University of California, Santa 

Cruz, written commun., 2006).

Black-Footed Albatross.—Densities of black-footed 

albatrosses are higher in the eastern North Pacific Ocean 

than Laysan albatrosses (fig. 2). One-year-old black-footed 

albatrosses have been observed in the Kuroshio-Oyashio 

Current and along the North Pacific Subtropical Convergence 

(Robbins and Rice, 1974). With increasing age, individual 

birds shift their range farther east, toward the west coast of 

North America. During the summer, adults are primarily 

observed offshore in the North Pacific, northeast of Japan and 

off North America (Robbins and Rice, 1974).

Black-footed albatrosses have long been known 

to occupy waters off the west coast of North America. 

Documented observations from ships indicate that from 

late winter (February) to fall (November), black-footed 

albatrosses were the primary albatross species observed 

between San Francisco and Honolulu (Fisher, 1945; Yocom, 

1947; Thompson, 1951). High densities of this species 

typically are observed offshore, over the cold waters of the 

California Current, as far south as Point Conception and the 

Channel Islands (Miller, 1936, 1940). Abundance of blackfooted albatrosses is markedly reduced outside the influence 

of the California Current (Miller, 1940; Thompson, 1951), 

and compared to Laysan albatrosses, black-footed albatrosses 

tend to remain in warmer waters along the southern edge 

of the transition zone (S. Shaffer, University of California, 

Santa Cruz, written commun., 2006; fig. 2). In the northern 

part of their range, black-footed albatrosses reach the Gulf of 

Alaska and the Aleutian Islands in summer, where their range 

overlaps with Laysan albatrosses. Black-footed albatrosses 

are most abundant over shelf breaks and along the boundaries 

of water masses (Wahl and others, 1989; McDermond and 

Morgan, 1993). 

At a “meso-scale,” distances as far as 12 km, the 

distribution of black-footed albatrosses is correlated with the 

presence of fishing vessels (Wahl and Heinemann, 1979). 

Black-footed albatrosses actively feed on fishing offal and 

discards, and their abundance is significantly affected by the 

presence of fishing boats (Hyrenbach, 2001).

Satellite tracking of black-footed albatrosses from the 

California Current System during summer indicates that 

they either remain in the area where they were captured 

(Hyrenbach and Dotson, 2003) or make long trips to the 

central and western Pacific Ocean in association with waters 

of the Transition Domain (Hyrenbach and others, 2005).
8 Status Assessment of Laysan and Black-Footed Albatrosses, North Pacific Ocean, 1923–2005

Natural History

Laysan Albatross

Breeding Cycle

Laysan albatrosses have a well-defined breeding cycle 

with little annual or inter-island variation. Males arrive first at 

the nesting colonies in late October to early November. Most 

breeding birds return to the colony by the end of November, 

about 10–14 days later than black-footed albatrosses (Frings 

and Frings, 1961). The first eggs are laid November 15–20, 

and most eggs are laid by mid-December (Rice and Kenyon, 

1962b; Fisher, 1969; U.S. Fish and Wildlife Service, unpub. 

data, 1980–2005). The incubation period averages 65 days 

(Rice and Kenyon, 1962b; Fisher, 1971b) and is longer than 

expected for an egg of its size, similar to other Procellarids 

and tropical seabirds (Whittow, 1984). The first eggs hatch in 

mid- to late January and most hatch by mid-February (Rice 

and Kenyon, 1962b; Fisher, 1971b; U.S. Fish and Wildlife 

Service, unpub. data, 1980–2005). Adults brood chicks for 

several days and continue to attend the chick for about 1 

month (guard phase), after which the adults spend most of 

their time at sea, returning to land only to feed the chick. The 

chick rearing period averages 165 days (Rice and Kenyon, 

1962b; Fisher and Fisher, 1969; U.S. Fish and Wildlife 

Service, unpub. data, 1980–2005), with the earliest chicks 

fledging in mid-June. Most fledging occurs in July, with a few 

individuals remaining as late as August. By the last week of 

July, adults are seldom seen at the colonies (Rice and Kenyon, 

1962b; Fisher, 1969). 

Nests and Nest Spacing

Laysan albatrosses are colonial breeders that typically 

nest near the center of the island on sheltered, flat areas 

surrounded by vegetation (Frings and Frings, 1961; Howell 

and Bartholomew, 1961; Rice and Kenyon, 1962b). Before 

egg laying, the female forms a shallow depression in the 

vegetation or substrate, although most of the nest construction 

is done by the male during the first incubation shift (Fisher, 

1971b). The rim of the nest is built by gathering soil, sand, 

vegetation, and other material from around the nest. The 

completed nest, including the depression surrounding the nest, 

is 85–100 cm in diameter and about 15–20 cm high (Rice and 

Kenyon, 1962b; Fisher, 1971b). 

 Nest densities vary with habitat. In 1958, the highest 

densities at Midway Atoll (0.0845 nests/m2

) were observed 

on Eastern Island in open, grassy areas with scattered trees 

(Frings and Frings; 1961). By 2005, the Laysan albatross 

population had substantially increased at Midway Atoll. 

The highest nest densities were in the southwestern sectors 

of Eastern Island (0.193–0.240 nests/m2

) and on Sand 

Island in the open, grassy areas that had been managed 

as parade grounds and antennae fields by the U.S. Navy 

(0.166–0.214 nests/m2; U.S. Fish and Wildlife Service, unpub. 

data, 1980–2005). The highest nest densities on Sand Island 

were in areas dominated by introduced turf grasses that were 

regularly mowed. In contrast, nest densities were lowest in 

open, sandy areas and areas of dense, tall vegetation such as 

the native beach naupaka, Scaevola taccada (U.S. Fish and 

Wildlife Service, unpub. data, 1980–2005). At Laysan Island, 

most birds nest in association with the native bunch grass 

(Eragrostis variabilis), the dominant vegetation of the island 

interior, but the highest densities are in the low, flat areas 

surrounding the lagoon and the guano hardpan created by past 

mining operations (Ely and Clapp, 1973).

Breeding Site and Mate Fidelity

Laysan albatrosses are monogamous with long-term pair 

bonds commonly retained until death or disappearance of a 

mate (Whittow, 1993a). Rice and Kenyon (1962b) observed 

only a few occasions (2.1 percent) where both birds returned 

with new mates in subsequent breeding attempts. 

 Laysan albatrosses exhibit high fidelity to their natal 

islands and nesting sites (Fisher, 1971a) with limited dispersal 

to other islands. In a study of banded birds at Midway Atoll, 

Fisher and Fisher (1969) concluded that Laysan albatrosses 

rarely visited islands other than their natal or breeding island. 

Most birds that did visit other islands were subadults. Firsttime breeders commonly build their first nests close to their 

hatch site with males (median = 12.3 m, range = 2.4–49.8 m) 

nesting closer to their hatching location than females 

(median=24 m, range = 2.4–42 m; Fisher, 1971a). Established 

pairs return to almost the same exact location to breed. At 

Midway Atoll, returning pairs nested within 1–6 m of where 

they nested in previous years (Rice and Kenyon, 1962b; 

Fisher, 1971a).

Demography and Limiting Factors

Breeding Age.—Laysan albatrosses can breed as early 

as 5 years of age (Fisher and Fisher, 1969). The mean age of 

first breeding is 8 to 9 years with males starting a year earlier 

than females (Fisher, 1975b). Nearly all birds begin breeding 

by age 12, with only a small percentage starting as late as 

16 years (Van Ryzen and Fisher, 1976).

Fecundity.—Females lay only one egg per season, and 

they do not relay if the egg is lost (Fisher, 1968). Although 

physiologically capable of producing an egg every year 

(Whittow, 1993a), most females periodically skip a breeding 

season. Fisher (1976) conducted a study at Midway Atoll 
Natural History 9

(1960 to 1973) and found that breeding frequency was affected 

by food availability, characteristics of the pair bond, breeding 

experience, previous season’s breeding success, and possibly 

gender. For birds in which the pair bond was maintained over 

the 10–13 year study, the mean breeding frequency per pair 

per year ranged from 0.82 to 0.86. Mean breeding frequency 

decreased to 0.71, 0.64, and 0.57 for albatrosses with two, 

three, and four different mates, respectively. Albatrosses 

that lose a mate, through widowing or other reasons, lost 

on average 1.4 (males) and 1.9 (females) breeding seasons 

before resuming breeding with a different mate (Fisher, 1976). 

Inexperienced breeding birds had lower breeding frequencies 

than experienced birds (mean = 0.59 during the first 5 years), 

and more than one-half of young pairs did not breed in the 

year following their first attempt (Fisher, 1976). Albatrosses 

that successfully raised a chick had a higher probability of 

skipping the next breeding season than those that lost their egg 

or chick (Rice and Kenyon, 1962b).

Breeding Success.—Reproductive success at French 

Frigate Shoals (mean = 0.64, SD = 0.19, n = 25 years; U.S. 

Fish and Wildlife Service, unpub. data, 1980–2005) from 1980 

to 2004 was comparable to that of Midway Atoll from 1961 to 

1972 (mean = 0.63, SD = 0.1, n = 4 years; Fisher, 1975a), but 

more recent data (1992–2001) indicate a lower success rate at 

French Frigate Shoals (mean = 0.50, SD = 0.20, n = 8 years; 

U.S. Fish and Wildlife Service, unpub. data, 1980–2005). 

The lowest success rates were calculated for Laysan Island 

(mean = 0.24, SD = 0.05, n = 4 years) from 1992 to 1995 

(U.S. Fish and Wildlife Service, unpub. data, 1980–2005). 

The primary cause of nest failure was desertion by one parent, 

but other sources include flooding, oceanographic anomalies, 

rat predation, and strong storms (Fisher, 1971b, 1975a; 

Woodward, 1972; U.S. Fish and Wildlife Service, unpub. data, 

1980–2005). Storms with high waves that completely wash 

over small islets may cause higher nest loss than nest desertion 

at some sites. These storms have little effect on adult survival 

(Fisher, 1975a, 1976).

Fledglings are susceptible to many sources of mortality. 

After leaving the nest area, young albatrosses congregate 

along the beaches for several days before leaving the island, 

and many die of starvation during this period (Rice and 

Kenyon, 1962b; Fisher and Fisher, 1969). During their first 

flights to sea, young albatrosses are susceptible to predation by 

tiger sharks (Galeocerdo cuvieri) or may become water-logged 

and drown. Fisher (1975a) estimated that 3.5–10 percent of 

chicks fledged from the nest did not reach the open ocean.

 The breeding period is a time of high-energy demand. 

Breeding adults lose as much as 26 percent of their body 

mass between when they arrive at the colony site and when 

their chicks reach peak mass (Fisher, 1967). Albatrosses may 

need to reach a minimum body weight to attempt breeding 

(Fisher, 1967), and birds that skip breeding most likely did not 

reach this threshold. Fisher (1967) found that non-breeding 

birds had body masses that were 8–11 percent lower than 

those of breeding birds. If adults with low body weights 

initiate breeding, they may be more susceptible to deserting 

the nest due to depletion of energy reserves. Therefore, food 

availability during non-breeding and breeding seasons is likely 

to affect breeding attempts and their success.

Juvenile and Adult Survival.—A few subadults return to 

the colony when they are 2 years old, but most wait until they 

are 4 years of age (Fisher, 1969). USFWS initiated monitoring 

to estimate adult survival rates in 2005 but currently, the 

only available information is from Fisher’s work conducted 

at Midway Atoll from 1961 to 1973 (Fisher, 1975a). Annual 

survival rates of 0.91 were estimated for juveniles (fledging to 

4 years old). Annual survival rates were 0.982 for individuals 

between 4 and 8 years old, when Laysan albatrosses begin 

breeding. Once adults start breeding their survival rates 

decrease, probably due to the high energetic costs associated 

with egg-laying and chick-rearing. However, Fisher (1975a, 

1975b) found first-time breeders had higher annual survival 

than experienced breeders (0.960 versus 0.946, respectively), 

perhaps because they had lower breeding frequencies and 

success.

Predators

The only known predators of Laysan albatrosses are tiger 

sharks and introduced mammals, including rats, mongooses, 

dogs, cats, and pigs. Tiger sharks prey on fledglings when 

first learning to fly. Shark numbers vary from year to year 

(Rice, 1959), but are present during fledging at all NWHI that 

support large albatross colonies.

Polynesian rats (Rattus exulans) killed nesting adults and 

chicks on Green Island, Kure Atoll (Kepler, 1967; Woodward, 

1972), until rats were eradicated in 1995 (C. Vanderlip and A. 

Marie, Hawai`i Department of Land and Natural Resources, 

unpub. data, 2004). Rat predation varied annually with almost 

no predation in some years and close to 100 percent chick 

mortality in other years (Woodward, 1972). At Midway Atoll, 

black rats (Rattus rattus) preyed on chicks and abandoned 

eggs, but they did not appear to attack healthy chicks or 

incubating adults (Fisher, 1971b). Rats were eradicated from 

Midway Atoll in 1996 (U.S. Fish and Wildlife Service, 2005). 

On the main Hawaiian Islands, feral and domestic dogs and 

cats kill albatross adults and chicks, and predator control 

programs are needed to protect nesting colonies (Mitchell 

and others, 2005; U.S. Fish and Wildlife Service, 2005). 

Mongooses are suspected egg predators. In addition, cats and 

dogs are important predators on the Mexican islands. The 

smaller offshore islets that are free of predators and human 

disturbance provide refuge for these colonies (Pitman and 

others, 2004). Feral pigs threatened the albatross colony on 

Clarion Island until they were eradicated in 2001 (Island 

Conservation and Ecology Group, 2001).
10 Status Assessment of Laysan and Black-Footed Albatrosses, North Pacific Ocean, 1923–2005

Diet and Foraging Behavior

Laysan albatrosses eat squid, fish, and other invertebrates 

and will scavenge on fisheries offal (fish scraps and guts) 

when available (Whittow, 1993a). Based on their diet and high 

rhodopsin (a visual pigment that enhances nocturnal vision) 

levels in their eyes, Laysan albatross were believed to feed at 

night on vertically migrating squid, when squid are near the 

surface (Harrison and others, 1983). Pitman and others (2004) 

found deep-water squid species in stomach samples of Laysan 

albatrosses from Guadalupe Island, Mexico, and suggested 

that Laysan albatrosses fed during the day by scavenging on 

squid that died after mating and floated to the surface.

During the breeding season, Hawaiian albatrosses fed 

their chicks primarily squid (65 percent), fish (9 percent), 

crustaceans (9 percent), and coelenterates (4 percent by 

volume; Harrison and others, 1983). Less than 6 percent of 

the squid were identified, and flying squid (Ommastrephidae) 

dominated those that were identified (Harrison and 

others, 1983). Pitman and others (2004) identified more 

than 97 percent of the cephalopod beaks in the samples 

from Mexico. Many families were represented (including 

Cranchiidae, 32 percent; Histioteuthidae, 27 percent; and 

Gonatidae, 20 percent), but not Ommastrephidae. The reason 

for this discrepancy is unknown, but the small percentage 

of squid identified in the Hawaiian study could be a factor. 

Pitman and others (2004) suggest that either the Hawaiian 

samples reflected the diets of birds scavenging from the North 

Pacific driftnet fishery, or they fed in a different region than 

birds from Mexican colonies.

Laysan albatrosses extensively scavenged on North 

Pacific driftnet fisheries while this fishery was active from 

1978 to 1992 (Gould and others, 1997). The main prey 

species scavenged from the nets were neon flying squid 

(Ommastrephes bartrami) and Pacific pomfret (Brama 

japonica), which accounted for 68 and 14 percent by mass, 

respectively, of stomach samples from collected birds killed 

as bycatch. Among the prey items that were highly digested, 

and thus thought to be caught away from the nets, were 

myctophid fish (Electrona risso, Symbolophorus californiense, 

Lampanyctus jordani) and Pacific saury (Cololabis saira), all 

occurring in greater than 5 percent of the stomach samples 

(Gould and others, 1997).

 Pacific saury is a pelagic, fast-growing fish with 

high commercial value found in the North Pacific Ocean 

from Japan to the Gulf of Alaska and southward to Mexico 

(Eschmeyer and others, 1983). Pacific saury was documented 

by Harrison and others (1983) as occurring in Midway Atoll 

samples during the winter, but not from other islands. This 

prey species also was found in diet samples from Laysan 

albatrosses but not black-footed albatrosses. These results 

suggest that small, schooling fish are important prey for 

Laysan albatrosses foraging in the western Pacific Transitional 

Zone and these results agree with the higher densities of 

Laysan albatrosses documented in this zone during June–

September by Gould and others (1998).

Stable isotope analysis (δ13C and δ15N) of the birds 

killed in driftnet fisheries indicated that adult Laysan 

albatrosses fed at a lower trophic level than juveniles (Gould 

and others, 1997), suggesting that juveniles may have had a 

higher association with the driftnet fisheries. This agrees with 

the high proportion of juveniles salvaged from this fishery.

Black-Footed Albatross

Breeding Cycle

Black-footed albatrosses also have a well-defined 

breeding cycle with little annual or inter-island variation. Birds 

arrive at the islands in mid- to late October. The first eggs are 

laid November 8–18 and most eggs are laid by early to midDecember, although a few eggs are laid through the end of the 

month (Rice and Kenyon, 1962b; Woodward, 1972; U.S. Fish 

and Wildlife Service, unpub. data, 1980–2005). The incubation 

period averages 66 days (Rice and Kenyon, 1962b) and, 

similar to other Procellarids and tropical seabirds, is longer 

than expected for an egg of this size (Whittow, 1984). The first 

eggs hatch in mid-January and most hatch by early February 

(Rice and Kenyon, 1962b; Woodward, 1972; U.S. Fish and 

Wildlife Service, unpub. data, 1980–2005). A few eggs hatch 

as late as February 20–22 (U.S. Fish and Wildlife Service, 

unpub. data, 1980–2005). Adults brood the chicks for several 

days and continue to attend the chick for about 1 month (guard 

phase), after which the adults spend most of their time at 

sea, returning to the island only to feed the chick. The chickrearing period averages 150 days (Rice and Kenyon, 1962b; 

Woodward, 1972) with the earliest fledging of chicks in early 

June. Most fledging occurs from mid-June to mid-July with a 

few individuals remaining as late as August. Adults are seldom 

seen at the colonies after early June (Rice and Kenyon, 1962b; 

Woodward, 1972; Whittow, 1993b).

Nests and Nest Spacing

Black-footed albatrosses are colonial nesters. Their nests 

consist of a shallow depression in loose, sandy substrate, 

surrounded by a rim of packed sand a few centimeters high. 

Nests are most common along wind-swept, sandy shores, or 

along the periphery of vegetation (Frings and Frings, 1961; 

Howell and Bartholomew, 1961; Rice and Kenyon, 1962b). 

At Midway Atoll and French Frigate Shoals, the birds also 

nest in areas of low-growing vegetation. Fisher (1972) 

suggested that black-footed albatrosses nesting far from the 

beach in Midway Atoll’s vegetated habitats had initially nested 

in more typical sandy, shoreline habitat but that the vegetation 

and distance to sea had changed as a result of human 

manipulations. The highest nest densities at Midway Atoll in 

1960 and 2005 were comparable at 0.024 nest/m2

 (Robbins, 

1966) and 0.025 nest/m2

 (U.S. Fish and Wildlife Service, 

unpub. data, 1980–2005), respectively.
Natural History 11

Breeding Site and Mate Fidelity

Albatrosses are monogamous with pair bonds typically 

retained until death or disappearance of one mate (Whittow, 

1993b). Of 42 black-footed albatross pairs banded at French 

Frigate Shoals, 9.5 percent of females and 19 percent of males 

changed mates at least once during a 4-year study (U.S. Fish 

and Wildlife Service, unpub. data, 1980–2005). The other 

member of the pair did not return to the island prior to the 

mate change (U.S. Fish and Wildlife Service, unpub. data, 

1980–2005).

Most young birds return to their natal islands to breed 

with limited dispersal to other islands. Chicks banded at 

French Frigate Shoals, Pearl and Hermes Reef, and Midway 

Atoll were recaptured at Kure Atoll from 1963 to 1969, and 

32 of the 158 chicks from other islands subsequently nested 

at Kure Atoll (Woodward, 1972). Most (86 percent) of the 

albatrosses that were banded on other islands and recaptured 

at Kure Atoll had been banded as chicks (Woodward, 1972). 

Established pairs return to the same island and almost the 

same location to breed. Returning pairs nest on average within 

4.5–5.8 m of where they nested the previous year (Rice and 

Kenyon, 1962b; Robbins, 1966).

Demography and Limiting Factors

Breeding Age.—The earliest breeding age for blackfooted albatrosses is 5 years. The average age is 7 years 

(Viggiano, 2001).

Fecundity.—Females lay one egg per season and do not 

relay if the egg is lost (Rice and Kenyon, 1962b). Although 

females are physiologically able to breed every year, most do 

not. At Midway Atoll, most individuals (63 percent) nest in 

2 consecutive years, but only 42 percent nest in 3 consecutive 

years (Robbins, 1966). At French Frigate Shoals, 69 percent 

of the females and 72 percent of the males nested in any given 

year, and 41 percent of the females and 38 percent of the 

males nested in 4 consecutive years, 1991–94 (U.S. Fish and 

Wildlife Service, unpub. data, 1980–2005). Viggiano (2001) 

found the probability of breeding in a given year was related 

to molt and breeding success in the previous year. On average, 

75 percent of black-footed albatrosses that successfully 

fledged a chick bred the next year, while 83 percent of those 

that failed to fledge a chick bred the next year (Viggiano, 

2001).

Breeding Success.—Breeding success of black-footed 

albatrosses from egg to fledging was 0.42 (SD = 0.04, n = 

4 years) at Kure Atoll during the 1960s (Woodward, 1972). 

More recent studies at Midway Atoll (1992–2001) and French 

Frigate Shoals (1980–2004) indicate higher reproductive 

success, averaging 0.55 (SD = 0.16, n = 8 years) and 0.69 (SD 

= 0.11, n = 25 years), respectively (U.S. Fish and Wildlife 

Service, unpub. data, 1980–2005). The lowest success rates 

in recent years were measured at Laysan Island (1992–1995; 

mean = 0.40, SD = 0.02, n = 4 years; U.S. Fish and Wildlife 

Service, unpub. data, 1980–2005), a value similar to estimates 

from Kure Atoll during the era when rats were present 

(Woodward, 1972).

The primary factors contributing to breeding failure at 

Kure Atoll from 1963 to 1968 were adult desertion, winter 

storms, and rat predation (Woodward, 1972). Rats have been 

eradicated from all NWHI (U.S. Fish and Wildlife Service, 

2005). Because black-footed albatrosses nest closer to the 

ocean, they are more affected by winter storms than Laysan 

albatrosses. High waves destroy near-shore nests, and strong 

winds bury nests in sand, including the chick or in some cases 

the incubating adult (Fisher, 1971b; McDermond and Morgan, 

1993).

Juvenile and Adult Survival.—Juveniles return to the 

colony at the age of 3-4 years (Rice and Kenyon, 1962b). 

Annual survival rates from fledging to 5 years were estimated 

to be 0.75 at Kure Atoll (1960–68; Woodward, 1972). 

Viggiano (2001) estimated the annual survival rate of juveniles 

0–5 years old to be 0.79, 2–4 years old to be 0.89, and 

breeding adults to be 0.89 from French Frigate Shoals.

Predators

Tiger sharks prey upon fledglings of black-footed 

albatross during their first flights to sea (U.S. Fish and 

Wildlife Service, unpub. data, 1980–2005). On Kure Atoll, 

chicks were killed by Polynesian rats (Woodward, 1972). 

However, this is no longer a problem in the NWHI because 

rats have been eradicated from Midway and Kure Atolls (U.S. 

Fish and Wildlife Service, 2005).

Diet and Foraging Behavior

Black-footed albatrosses feed at the surface by surfaceseizing, contact dipping, and scavenging (Gould and others, 

1998). They eat squid, fish, and other invertebrates and 

scavenge fisheries offal when available (Whittow, 1993b). 

Most diet information is derived from two sources: 

Harrison and others (1983) and Gould and others (1997). 

Harrison and others (1983) collected regurgitated samples 

throughout the chick-feeding stage from birds in the Hawaiian 

colonies (1978–80), and Gould and others (1997) collected 

stomach samples from birds killed in the driftnet fisheries. 

During chick rearing, black-footed albatrosses in Hawai`i fed 

their chicks 50 percent fish, 32 percent squid, and 5 percent 

crustaceans on a volume basis, although these data may be 

biased due to the highly digested condition of the stomach 

contents. Main prey items identified were flyingfish ova, 

Family Exocoetidae (frequency of occurrence = 80.2 percent, 

volume = 44.2 percent); and squid, Family Ommastrephidae 

(frequency of occurrence = 11.7 percent, volume = 3.4 

percent; Harrison and others, 1983).
12 Status Assessment of Laysan and Black-Footed Albatrosses, North Pacific Ocean, 1923–2005

Squid and large-mesh driftnet fisheries operated from 

1978 to 1992, primarily in the Transitional Zone (35°–46°N 

and 145°W–145°E; Ito and others, 1993). Black-footed 

albatrosses scavenged extensively from nets, primarily on 

neon flying squid (Ommastrephes bartrami) and Pacific 

pomfret (Brama japonica), which accounted for 67 and 

18 percent mass, respectively (Gould and others, 1997). 

Highly digested items, thought to be consumed before the 

birds were entangled in the net, were primarily squids from 

the families Gonatidae (Gonatopsis, Berryteuthis, Gonatus), 

Cranchiidae (Leachia, Taonius, Galiteuthis), Onychoteuthidae 

(Onychoteuthis borealijaponicus), and Octopoteuthidae 

(Octopoteuthis deletron). All species represented greater 

than 5 percent frequency of occurrence (Gould and others, 

1997). These studies indicate that Laysan and black-footed 

albatrosses take similar prey items but in different proportions, 

which may reflect their different distributions at sea.

Habitat Requirements

One basic life-history characteristic of albatross species 

is the separation of nesting and foraging areas. Nesting of 

Laysan and black-footed albatrosses is restricted to oceanic 

islands. Laysan albatrosses prefer to nest on level areas in 

the interior of islands, typically in association with grass and 

other low vegetation, although dense vegetation precludes 

nesting (Frings and Frings, 1961; Howell and Bartholomew, 

1961; Woodward, 1972). By contrast, black-footed albatrosses 

primarily nest on sandy areas near the shore (Frings and 

Frings, 1961). At sea, both species widely range over the 

North Pacific (see section, “Geographic Distribution”).

Threats

Laysan and black-footed albatrosses face a wide range 

of threats at sea and on the breeding islands. Interactions with 

commercial fishing operations (bycatch), contaminants, and 

plastics threaten birds at sea, while invasive species (predators, 

plants, and invertebrates), contaminants, habitat degradation, 

and human disturbance threaten birds at nesting colonies. 

Changes associated with global climate change potentially 

threaten both species at sea and on breeding grounds.

Fishery Bycatch

Mortality due to fisheries is the primary factor 

threatening Laysan and black-footed albatross populations 

(Croxall and Gales, 1998; Gales, 1998; Cousins and Cooper, 

2000; Lewison and Crowder, 2003). To assess its effect on 

both species, we conducted a detailed analysis of all fisheries 

for which bycatch of Laysan and black-footed albatrosses 

has been documented. Bycatch refers to non-target species 

unintentionally caught in fishing gear. The three main fisheries 

for which bycatch data are available are high seas driftnet, 

Alaskan and Canadian demersal longline, and U.S. pelagic 

longline. Bycatch information for other longline fisheries, such 

as the U.S. West Coast groundfish fishery and foreign longline 

fleets, were not available at the time of these analyses.

Description of the Fisheries

High Seas Driftnet Fisheries.—Three general types of 

driftnet fisheries operated in the high seas of the North Pacific 

until 1992: (1) salmon driftnet fishery (Japan), (2) large-mesh 

driftnet fishery for billfish and tuna (Japan and Taiwan), and 

(3) squid driftnet fishery (Japan, the Republic of Korea, and 

Taiwan) (DeGange and others, 1993; Ogi and others, 1993). 

These fisheries used large nets, usually 15 to 60 km long, 

vertically suspended in the water, from the surface to 6 to 8 

m deep (DeGange and Day, 1991; Gong and others, 1993; 

Nakano and others, 1993). Due to the high rate of incidental 

mortality to seabirds, marine mammals, sea turtles, and nontarget fish by this fishing gear, a global moratorium on highseas pelagic driftnet fishing was adopted in December 1991 

(to be fully implemented by December 1992) by the United 

Nations (UN) General Assembly Resolution 46-215. However, 

a few vessels continue to illegally fish with driftnets in the 

North Pacific high-seas (National Marine Fisheries Service, 

2005). 

The Japanese high-seas salmon driftnet fishery operated 

from 1952 to1991 and was divided into mothership and 

land-based salmon fisheries (DeGange and Day, 1991; Ogi 

and others, 1993). The mothership salmon fishery operated 

primarily southeast of the westernmost Aleutian Islands, 

inside the U.S. exclusive economic zone (EEZ) (DeGange and 

others, 1993). This fishery peaked in 1959 and subsequently 

decreased until its closure in 1991. The land-based salmon 

fishery operated primarily off eastern Japan (DeGange and 

Day, 1991). This fishery reached its highest effort from 1955 

to 1976, then declined until being closed in 1991 (DeGange 

and Day, 1991; Ogi and others, 1993). During peak years, 

hundreds of thousands of kilometers of net were set each 

season. Albatross bycatch was not known to occur in the 

mothership fishery, but Laysan albatrosses were killed in the 

land-based salmon fishery (DeGange and Day, 1991; DeGange 

and others, 1993; Ogi and others, 1993).

The Japanese large-mesh driftnet fishery targeted striped 

marlin, broadbill swordfish, tuna, and albacore, whereas the 

Taiwanese fleet fished mostly for tuna (DeGange and others, 

1993; Ogi and others, 1993). The fishing grounds established 

by the Japanese government were between 10°–46°N and 

from 145°W to Japan, excepting the U.S. EEZ around Hawai`i 

(Nagao and others, 1993), but fishing effort was concentrated 
Threats 13

between 20°–40°N and 150°W–140°E (Nakano and others, 

1993). The Taiwanese fleet began fishing in 1980 and operated 

in most of the North Pacific. Laysan and black-footed 

albatrosses were killed in both the Japanese and Taiwanese 

fleets (Johnson and others, 1993; Ogi and others, 1993) prior 

to closure of the fishery in 1992 due to the UN ban.

 The squid driftnet fishery was composed of fleets 

from Japan, Korea, and Taiwan. This fishery started in 

1978, increased until 1985, and decreased until closing in 

1992 (DeGange and others, 1993). The targeted species was 

the neon flying squid. The fishery was concentrated in the 

Subtropical Convergence between 34°–46°N, with most of the 

fishing effort occurring in the western Pacific Ocean (Gong 

and others, 1993; Yatsu and others, 1993; Yeh and Tung, 

1993). A distributional analysis of seabird bycatch by the 

Korean fleet indicates two areas with high bycatch rates; one 

north of the Hawaiian Islands (165°–175°W) and the other 

off of Japan (142°–162°E, Gong and others, 1993). Large 

numbers of albatrosses were killed in these fisheries (Johnson 

and others, 1993; Ogi and others, 1993).

The UN moratorium only applied to high seas fisheries, 

therefore driftnet fisheries still exist in the Exclusive 

Economic Zones (EEZ) of some countries. Laysan albatrosses 

are killed in the Japanese salmon driftnet fishery in Russia’s 

EEZ (Artyukhin and Burkanov, 2000). In the U.S., large mesh 

gillnets are fished within the EEZ off California and Oregon, 

but no albatross bycatch has been recorded (Julian and 

Beeson, 1998). 

Longline Fishing.—Longline fishing is a commercial 

technique that deploys hundreds or thousands of baited hooks 

set on the seabed (demersal longlining) or in the water column 

(pelagic longlining). In this way, longlines can be used to 

target a variety of fishes from bottom-dwelling species, such 

as halibut, to tunas of the open seas (Brothers and others, 

1999). As surface-scavengers, albatrosses are drawn to fishing 

vessels to supplement their food with discards or by stealing 

baits from hooks. 

Demersal (bottom) longline fisheries primarily target 

halibut and other groundfish species. In the northern and 

northeastern Pacific Ocean, the primary species targeted are 

(from National Marine Fisheries Service, 2006; Fisheries 

and Ocean Canada, accessed January 24, 2009, at http://

www.pac.dfo-mpo.gc.ca/ops/fm/Groundfish/default_e.

htm) halibut (Hippoglossus stenolepis), Pacific cod 

(Gadus macrocephalus), Greenland turbot (Reinhardtius 

hippoglossoides), sablefish (Anoplopoma fimbria), rockfish 

species (family Scorpaenidae), lingcod (Ophiodon elongatus), 

and spiny dogfish (Squalus acanthias). Except for halibut, 

these fish are collectively referred to as groundfish, and the 

demersal longline fisheries for groundfish off of Alaska, 

Washington, Oregon, and California are managed by the 

National Marine Fisheries Service (NMFS). The halibut 

fishery is managed by the International Halibut Commission 

(IPHC). China, Taiwan, Japan, Korea, and Russia all operate 

demersal longline fisheries in the northwestern Pacific Ocean 

(Brothers and others, 1999).

Pelagic longline fisheries are the main fisheries 

currently operating in the central North Pacific Ocean and are 

considered the greatest threat to the black-footed albatross 

(Cousins and Cooper, 2000; Lewison and Crowder, 2003). 

The IUCN listed the black-footed albatross as Endangered 

and the Laysan albatross as Vulnerable in 2003 in response to 

the threat posed by this fishery (International Union for the 

Conservation of Nature and Natural Resources, 2004).

The Hawaii-based pelagic longline fleet operates from 

the Equator to 50°N, between 135°W and 170°E, with the 

highest fishing effort near the Hawaiian Archipelago (U.S. 

Fish and Wildlife Service, 2004b). However, the highest 

incidence of interactions with albatrosses occurs between 

25°–35°N and 140°W–175°E (U.S. Fish and Wildlife Service, 

2004b). The number of vessels fishing from Hawai`i increased 

in the late 1980s and peaked at 141 in 1991. The high bycatch 

rate of protected species (sea turtles, cetaceans, and seabirds) 

associated with the pelagic longline fisheries for broadbill 

swordfish (Xiphias gladius) led to the implementation of gear 

modifications and area closures. Due to the continued high 

bycatch of sea turtles (Kinan, 2003a, 2003b), the Hawaiibased longline fishery for swordfish was closed by a Federal 

court order in April 2001 (emergency rule 66 FR 31561) and 

ratified in 2002 (C.M. 67FR40232, June 12, 2002). In 2002, 

only 100 vessels were still active, all targeting tuna (U.S. 

Fish and Wildlife Service, 2004b). The primary species of 

tuna targeted are bigeye tuna (Thunnus obesus), albacore tuna 

(Thunnus alalunga), and yellow fin tuna (Thunnus albacares). 

The swordfish-directed sector of the fishery was reopened in 

Hawai`i on April 2, 2004 (69 FR 17329) under new mitigation 

requirements to reduce sea turtle bycatch (National Marine 

Fisheries Service, 2005, p. 138).

 Swordfish and tuna landings in California began in 1991. 

By 1994, 31 vessels were fishing in the same general region as 

Hawaii-based longliners, but landing their catches in southern 

California. All fishing was conducted outside California’s EEZ 

(U.S. Fish and Wildlife Service, 2004a). From 1995 to 2001, 

most of the landings in California were from fishing grounds 

around 135°–150°W during fall and winter, and moved west, 

north of Hawai`i during spring-summer. As a consequence 

of the area closures and increased regulation in the Hawaiian 

swordfish fishery, part of the Hawaiian fleet moved their base 

port to California (about 35 vessels in 2001), where gear and 

setting regulations were not in place. A voluntary observer 

program was initiated in October 2001 that became mandatory 

in August 2002 (U.S. Fish and Wildlife Service, 2004a). The 

West Coast longline swordfish fishery was closed in 2004 (69 

FR 11540, March 11, 2004; U.S. Fish and Wildlife Service, 

2004a).
14 Status Assessment of Laysan and Black-Footed Albatrosses, North Pacific Ocean, 1923–2005

There also are pelagic longline fleets from Japan, Korea, 

and Taiwan fishing for tuna and billfish in the North Pacific 

Ocean (Kinan, 2003a). Korean fleets fish south of 20°N 

(Lewison and Crowder, 2003) and thus, are not considered 

here. Information on fishing effort by these fisheries is 

available through the public domain database maintained 

by the Ocean Fisheries Program (OFP) for pelagic fisheries 

(primarily tuna) in the North Pacific Ocean. This database 

includes fishing effort from all fleets combined, including the 

U.S. (OFP-Public Domain Catch and Effort Data). However, 

no estimates of seabird bycatch or information on the use of 

mitigation measures to reduce seabird bycatch are available 

for International fleets.

Bycatch Estimation

The many fisheries operating in the North Pacific incur 

varying levels of albatross bycatch. Data sources for bycatch 

estimates are summarized in table 1, and detailed analyses and 

results for each fishery are presented in appendix A.

From 1950 to 1977, we estimated bycatch of Laysan 

albatrosses to be less than 6,000 albatrosses per year, but 

during the period of driftnet fishing, 1978 to 1992, bycatch 

increased to an estimated 27,800 albatrosses per year (fig. 3). 

For black-footed albatrosses, the bycatch estimates showed 

a bimodal distribution with a peak of 15,290 birds in 1961 

and a second peak of 16,215 birds in 1988 (fig. 4). The 1988 

Type of data Fishery Species Source Year

Driftnet Japanese land-based salmon LAAL DeGange and Day, 1991 1977–1987

Driftnet Japanese land-based salmon LAAL Ogi and others, 1993 1990

Driftnet Japanese large-mesh driftnet LAAL/BFAL Johnson and others, 1993; Ogi and others, 1993 1990

Driftnet Taiwanese driftnet: large mesh and squid LAAL/BFAL Johnson and others, 1993; Ogi and others, 1993 1990

Driftnet Japanese squid driftnet LAAL/BFAL Johnson and others, 1993; Ogi and others, 1993 1990

Driftnet Korean squid driftnet LAAL/BFAL Johnson and others, 1993; Ogi and others, 1993 1990

Driftnet Japanese total fishing effort LAAL/BFAL Yatsu and others, 1993 1982–1990

Demersal Longline Alaskan longline groundfish LAAL/BFAL Boldt, 2004; National Marine Fisheries Service, 

2005b

Demersal Longline Washington & British Columbia longlines LAAL/BFAL Smith and Morgan, 2005 

Demersal Longline Halibut fishery effort IPHC web page—http://www.iphc.washington.

edu/halcom/research/sa/sa.data/sa.data.html

Demersal Longline Halibut fishery effort for British Columbia Smith and Morgan, 2005 2000–2002

Demersal Longline Halibut, Gulf of Alaska and Aleutians LAAL/BFAL Geernaert and others, 2001 1998–1999

Demersal Longline Halibut fishery for British Columbia LAAL/BFAL Smith and Morgan, 2005 1999–2002

Pelagic Longline International pelagic longline fisheries effort Ocean Fisheries Program (OFP)—http://www.

spc.int/oceanfish/

Pelagic Longline Hawai`i fishing effort for tuna and swordfish Kinan, 2003a, 2003b, 2004; National Marine 

Fisheries Service, 2005a

Pelagic Longline Scientific observer program data National Oceanic and Atmospheric 

Administration Fisheries, Hawai`i

1994–2004

Table 1. Data sources used in bycatch estimations for Laysan (LAAL) and black-footed (BFAL) albatrosses.

peak was due to the combined effect of high-seas driftnet and 

longline fisheries. The estimated bycatch in demersal fisheries 

off Alaska represents only a small fraction of the 2005 

estimate of total bycatch (figs. 3 and 4), and, at the time of 

these analyses, the bycatch rate is unknown for either albatross 

species in the demersal longline fisheries off California, 

Oregon, and Washington.

Overall, the high-seas driftnet and longline fisheries 

have been the most important causes of mortality for Laysan 

and black-footed albatrosses over the past 50 years, but 

effects differ between species. Pelagic longlines have killed 

a large number of albatrosses each year since the fishery 

started in 1951. The driftnet fishery, primarily active from 

1978 to 1992, killed a disproportionately large number of 

black-footed albatrosses, and a significant number of Laysan 

albatrosses, in addition to other seabirds, marine mammals, 

sea turtles, and fish. Closure of the fishery in 1992 by a United 

Nations Resolution (National Marine Fisheries Service, 2005) 

significantly reduced the total number of albatrosses killed 

each year.

In contrast, albatross mortality in pelagic longline 

fisheries continues. This is especially worrisome because, 

while most U.S. and Canadian fisheries require use of 

mitigation measures and observer programs, there is no 

scientific observer program on the International pelagic 

longline fleet, thus preventing accurate estimates of total 

bycatch and hampering establishment of mitigation programs.
Threats 15

Figure 3. Total estimated number of Laysan albatrosses killed by commercial fisheries in the North Pacific Ocean, 1951–2005. 

Figure 4. Total estimated number of black-footed albatrosses killed by commercial fisheries in the North Pacific Ocean, 

1951–2005. 

tac_08_9354_0255_Albatrosses_Fig03

0

5,000

10,000

15,000

20,000

25,000

30,000

35,000

40,000

1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005

ESTIMATED MORTALITY

Total

Pelagic longline

Driftnets

Demersal longline

Alaska trawl

Estimated Number of Laysan Albatrosses Killed

 solid line = mean

 dashed line = 95-percent confidence interval

0

5,000

10,000

15,000

20,000

25,000

1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005

ESTIMATED MORTALITY

Total

Pelagic longline

Driftnet

Demersal longline

Estimated Number of Black-Footed Albatrosses Killed

 solid line = mean 

 dashed line = 95-percent confidence interval
16 Status Assessment of Laysan and Black-Footed Albatrosses, North Pacific Ocean, 1923–2005

Predation

Prior to human influence, albatrosses were threatened 

by few, if any, predators on their remote nesting islands. 

Tiger sharks are the only native predators in the NWHI. All 

introduced mammals have been removed from the NWHI, 

with the exception of the house mouse (Mus musculus) 

on Midway Atoll (U.S. Fish and Wildlife Service, 2005). 

Although currently not a threat, the house mouse has been 

identified as an important predator of Tristan albatross 

(Diomedea dabbenena) chicks on Gough Island, and they 

potentially pose a threat on Midway Atoll in the future (Angel 

and Cooper, 2006; Wanless and others, 2007). 

Dogs nearly extirpated several albatross colonies along 

Kaua`i’s north shore until fences were installed at Kilauea 

Point National Wildlife Refuge (NWR) and predator control 

programs were instituted (U.S. Fish and Wildlife Service, 

2005). Dogs, cats, rats, and mongooses are an on-going 

problem at the Ka`ena Point Natural Area Reserve colony on 

O`ahu where the Hawai`i Department of Land and Natural 

Resources oversees control programs.

In Mexico, the Clarion raven (Corvus corax clarionensis) 

and the Clarion racer (Masticophis anthonyi) are the only 

native predators that may take albatross chicks or eggs on 

Clarion Island. Observations are limited and the impact of 

this predation is unknown (B. Keitt, University of California 

Santa Cruz, written. commun., 2008). Predation by introduced 

cats at Guadalupe Island limits the growth of populations 

at this site. If not controlled, cat predation could eventually 

cause extirpation of the colonies on the main island. Nearby 

islets provide secure nesting habitat because the islets are 

predator-free and undisturbed by humans (Pitman and others, 

2004). Predator control programs by Grupo de Ecologia y 

Conservación de Islas and the Mexican Natural Resource 

agency SEMARNAT have been effective in limiting predation 

on Guadalupe Island (Keitt and others, 2006). Dogs have been 

eradicated from Guadalupe Island and introduced pigs have 

been eradicated from Clarion Island (Aguirre-Munoz and 

others, 2008). 

Presence of introduced predators on former breeding 

islands in the Marshalls, Marianas, and Japan could be a factor 

precluding albatrosses from reoccupying some of these sites.

Introduced Species

In addition to the mammalian predators (see section, 

“Predation”), introduced herbivores, invertebrates, and plants 

also have had major impacts on albatross populations and 

their nesting habitats. Rabbits were introduced to Laysan and 

Lisianski Islands in 1903 (Tickell, 2000) and to Pearl and 

Hermes Reef probably during the era of feather poaching 

(Amerson and others, 1974). Rabbits almost completely 

denuded these islands of vegetation before the animals died 

of starvation or were eradicated from 1915 to 1928 (Ely and 

Clapp, 1973; Amerson and others, 1974; Clapp and Wirtz, 

1975). In Mexico, rabbits continue to degrade habitat on 

Clarion Island, but sheep have been eradicated from Clarion 

Island and goats have been eradicated from Guadalupe Island 

(Aguirre-Munoz and others, 2008).

Mosquitoes, a vector for avian pox, were introduced 

to the main Hawaiian Islands in 1826 (Warner, 1968) and 

also occur on Midway Atoll. The effect of introduced ants at 

colonies in Hawai`i and Mexico is unknown.

Many exotic plant species have been introduced to the 

islands. Some of these plants have enhanced albatross nesting 

habitat although others have seriously degraded it (see section, 

“Threats – Habitat Loss and Degradation”).

Habitat Loss and Degradation

The Northwestern Hawaiian Islands (NWHI) have 

undergone a series of physical changes during the past century 

as a result of human occupation. A detailed account for each 

breeding island is presented in appendix B.

Invasive Plants

Over the past century, many non-native plant species 

have been introduced to the NWHI. Of these, ironwood trees 

(Casuarina equisetifolia) and golden crown-beard (Verbesina 

encelioides) probably have had the greatest negative impact 

on albatross populations. Ironwood trees are particularly 

abundant at Sand Island (Midway Atoll), where they present 

an obstacle for flight (U.S. Fish and Wildlife Service, 2005). 

Laysan albatross will nest under the closed-canopy ironwood 

forest, but densities in this habitat are lower than in habitats 

with low vegetation. Ironwood trees were eradicated from 

Eastern Island (Midway Atoll) during the past decade. The 

ironwood trees on Sand Island also support the largest colonies 

of white terns (Gygis alba) and black noddies (Anous minutus) 

in the Hawaiian Islands (U.S. Fish and Wildlife Service, 

2005). Therefore, complete removal of ironwood trees would 

negatively affect these bird species. Golden crown-beard is 

an aggressive, woody herb that forms tall, dense stands that 

can reduce ground access for surface-nesting species, such 

as albatrosses. This plant is well established at Kure Atoll, 

Midway Atoll, and Pearl and Hermes Reef. Golden crownbeard also provides habitat for introduced mosquitoes that 

spread avian pox (U.S. Fish and Wildlife Service, 2005).

Urban and Military Development

In the past, loss and degradation of habitat due to military 

activities were a major issue (see section, “Threats – Conflicts 

with Military Activities”). The closure of military bases at 

Midway Atoll, Kure Atoll, and French Frigate Shoals, and 

the removal of many of the associated structures (buildings, 
Threats 17

antennas, fuel tanks, streetlights, etc.) has improved habitat 

quality, reduced collision-associated mortality, and led 

to increases in the size of albatross populations on these 

islands. However, issues such as lead and organochlorine 

contamination remain at these former bases (see section, 

“Threats – Pesticides and Other Contaminants”). Currently 

(2005), loss of habitat to urban development is not a major 

threat to the small Laysan albatross colonies on the main 

Hawaiian Islands, but this could become a factor in the future.

Conflicts with Military Activities

There is a long history of military occupation on islands 

that support albatross colonies. These occupations have had 

positive and negative effects on albatrosses. Kure Atoll, 

Midway Atoll, French Frigate Shoals, Johnston Atoll, Minami 

Torishima, and Iwo Jima all supported military bases in the 

past, and active installations still exist at Wake Atoll and in the 

main Hawaiian Islands of Kaua`i at the Pacific Missile Range 

Facility and O`ahu at the Marine Corps Base Hawaii. Many of 

these bases were established during WWII.

Albatrosses have been affected directly and indirectly by 

military activities. An estimated 58,000 Laysan and almost 

3,000 black-footed albatross adults were killed at Midway 

Atoll from 1957 to 1964 (table 2) in control programs intended 

to reduce albatross interference with aircraft operations 

(Kenyon and others, 1958; Rice, 1959; Robbins, 1966). Fisher 

(1966b) estimated an additional 3,000 breeding albatrosses 

were indirectly killed each year by antenna collisions and 

other activities, such as construction and vehicle collisions. 

Loss of habitat to roads, buildings, runways, and other 

development associated with military bases severely restricted 

nesting space. Aircraft use of runways on Eastern Island, 

Midway Atoll, was discontinued after WWII, and although 

the runways are badly degraded, they continue to be a major 

feature of Eastern Island. Thousands of albatrosses nest on 

old runways, and some albatross have swollen feet and leg 

joints that may be related to landing and nesting on the hard 

surface. Adult albatrosses are no longer intentionally killed 

at U.S. military bases, but in the main Hawaiian Islands, 

albatrosses are discouraged from nesting at the Pacific Missile 

Range Facility (Kaua`i), Dillingham Airfield, and the Marine 

Corps Base Hawaii (O`ahu) to minimize the chance of aircraft 

collisions (Whittow, 1993a). Nests are destroyed, adults are 

harassed, and adults and eggs are relocated to areas off base.

Throughout the Pacific, military transports have 

introduced exotic species (plants and animals) that degrade 

habitat or prey on native species. Invasive species, habitat 

degradation, and toxic chemicals continue to affect albatross 

survival long after the end of military occupation (see section, 

“Threats—Pesticides and Other Contaminants”).

Date and 

species

Estimated number of albatrosses killed on Midway Atoll 

Eastern Island Sand Island

Antennas

Aircraft 

and road 

collisions

Experiments 

and 

bulldozing

Control 

programs

1956: LAAL 2,900

 BFAL 5

1957: LAAL 2,900 4,339 4,000c + 415ad 4,688

 BFAL 5 328 800c + 25ad 100

1958: LAAL 2,900 4,668 29,764

 BFAL 5 352 277

1959: LAAL 2,900 2,662

 BFAL 5 200

1960: LAAL 2,900 2,662 1,204 9,908

 BFAL 5 200 1,430 92

1961: LAAL 2,900 2,662

 BFAL 5 200

1962: LAAL 2,900 2,662

 BFAL 5 200

1963: LAAL 2,900 2,662 928

 BFAL 5 200 294

1964: LAAL 2,900 2,662 13,810

 BFAL 5 201 2,420

1965: LAAL 2,900 2,662

 BFAL 5 200

1966: LAAL 2,900

 BFAL 5

1967: LAAL 2,900

 BFAL 5

Total: LAAL 34,800 27,641 6,547 58,170

Total: BFAL 60 2,081 2,549 2,889

Table 2. Estimated number of Laysan (LAAL) and black-footed 

(BFAL) albatrosses killed on Midway Atoll in control programs, 

experiments, and collisions with antennas, and aircraft and road 

collisions, 1956–67.

[Antennas: Estimates from Fisher (1966c) made during 1965 breeding 

season. Aircraft and road collisions: Number of aircraft landings/take-offs 

from Kenyon and others (1958), Rice (1959), and Robbins (1966). Number 

of birds killed in road collisions were only recorded by Kenyon and others 

(1958). The number of birds killed by aircraft collisions and road accidents 

were assumed to be related and followed the relation: LAAL= 2.511 and 

BFAL= 0.190 birds killed per landing/take-off (from Kenyon and others, 

1958). Relation between Walkers: Breeding birds is LAAL= 0.42:0.58 and 

BFAL= 0.45:0.55, with ‘Walkers’ including juveniles and non-nesting adults 

(Robbins, 1966). Experiments and bulldozing: Includes birds killed (Kenyon 

and others, 1958) in experimental plots and during bulldozing operations 

to flatten plots around runways (c=chicks, ad=adults), plus the number of 

breeding adults precluded from nesting due to the previous year’s blacktopping of zone-9 (1960) and zone-8 (1963) (census data are from Robbins, 

1966). Control programs: Includes birds documented in Kenyon and others 

(1958), Rice (1959), Robbins (1966), and Fisher (1966a). Breeding seasons 

refer to the year of chick hatching/fledging]
18 Status Assessment of Laysan and Black-Footed Albatrosses, North Pacific Ocean, 1923–2005

Some aspects of military occupation appear to have 

benefited albatrosses. Occupation of Midway Atoll early in 

the 20th century probably kept feather hunters from depleting 

the albatross colonies, as they did on other Northwestern 

Hawaiian Islands (Tickell, 2000). Activities on remote islands 

commonly included augmentation of land area through 

dredging and spoil deposition. Small, sandy islets, typical of 

atolls, were stabilized with exotic plants, especially grasses, 

and installation of seawalls or other reinforcements. Although 

significantly degrading the native ecological communities, 

these activities increased the land area and enhanced albatross 

nesting habitat on some islands. In 2005, the largest Laysan 

and black-footed albatross colonies in the World are located at 

Midway Atoll.

Pesticides and Other Contaminants

Metals

Lead poisoning has been documented in Laysan albatross 

chicks on Sand Island, Midway Atoll, in the immediate 

vicinity of former military and cable company buildings 

(Sileo and Fefer, 1987; Sileo and others, 1990a). Metal 

exposure is through ingestion of lead-based paint chips from 

deteriorating buildings (chips: 84,316 ± 16,183 ppm lead and 

39.9 ± 5.8 ppm mercury; Finkelstein and others, 2003). Lead 

concentrations in the livers of poisoned chicks range from 6 to 

245 ppm. These chicks exhibit symptoms such as drooping 

wings and yellow, watery bile (Sileo and Fefer, 1987; Sileo 

and others, 1990a). Lead poisoning is rare in black-footed 

albatross chicks, which typically do not occur near buildings, 

and it has not been observed in adults of either species (Sileo 

and Fefer, 1987).

In 2005, areas around contaminated buildings were 

covered to dissuade albatrosses from nesting nearby. Although 

successful in minimizing the number of nests in those areas, 

once mobile, chicks wandered into contaminated areas and 

succumbed to lead poisoning. It is estimated that as many as 

10,000 chicks per year, are potentially exposed to lethal levels 

of lead from ingestion of lead-based paint (approximately 

2–3 percent of the chicks hatched; M. Finkelstein, University 

of California, Santa Cruz, written commun., 2006) and 

perhaps more importantly, birds not exhibiting overt 

symptoms could still have immunological and neurological 

toxic effects that could decrease fitness and survival 

(Finkelstein and others, 2003).

Concentrations of mercury (Hg) and cadmium (Cd) 

also are high in Laysan and black-footed albatrosses, but no 

negative effect has been reported. In 1969, high concentrations 

of Hg (mean = 104 ppm, range: 0–250 ppm Laysan albatross; 

mean = 75 ppm, range: 50–120 ppm black-footed albatross) 

were found in the subcutaneous fat of adults, but no sign 

of poisoning was detected (Fisher, 1973). In 1985, liver 

concentrations of Hg and Cd in Laysan albatross were 

11.4 and 15.1 ppm wet weight, respectively (Honda and 

others, 1990). Liver concentrations of Hg in black-footed 

albatross were 95.4 ppm (Honda and others, 1990) and 

279 ppm (Kim and others, 1998), and Cd concentrations were 

22.0 ppm (Honda and others, 1990) and 70.6 ppm (Kim and 

others, 1998) wet weight. Honda and others (1990) suggested 

that these concentrations may be the result of natural 

background levels and low elimination rates in albatrosses 

because there was no visible sign of poisoning.

Organochlorine Contaminants

Laysan and black-footed albatrosses from the Hawaiian 

Islands exhibit high concentrations of organochlorine 

contaminants, but black-footed albatrosses have significantly 

greater accumulations (Fisher, 1973; Jones and others, 

1996; Auman and others, 1997; Guruge and others, 2001a). 

Organochlorine compounds, such as PCBs and DDE (main 

breakdown product of DDT), are known to reduce avian 

fecundity through embryo mortality, teratogenic development, 

and eggshell thinning; effects known as the Great Lakes 

Embryo Mortality, Edema, and Deformities Syndrome 

(GLEMEDS; Gilbertson and others, 1991). Contaminant 

levels in Laysan albatross eggs were lower than threshold 

levels expected for eggshell thinning or other dioxin-like 

effects (table 3), and thus no direct GLEMEDS risk is believed 

to be present (Jones and others, 1996; Auman and others, 

1997; Guruge and others, 2001b). Contrary to this finding, 

Guruge and others (2001b) estimated a Hazard Index4 greater 

than 20, which is within the range where population-level 

effects are expected. Field studies have found no measurable 

effect (Auman and others, 1997; Ludwig and others, 1998). 

Concentrations of PCBs and DDE in Laysan and black-footed 

albatrosses have increased 130 to 360 percent in the last 

decade (Finkelstein and others, 2006).

Black-footed albatrosses from Hawai`i contain high 

concentrations of organochlorine contaminants that may 

cause dioxin-like effects. Black-footed albatross eggs contain 

toxic equivalents of PCB, DDE, and TCDD (table 4), known 

to cause GLEMEDS effects in fish-eating birds (Auman and 

others, 1997; Guruge and others, 2001b). Hazard Indices for 

black-footed albatross eggs were 1.7–9.7 for PCBs, 0.51 for 

DDE, and 12–86 for TCDD (Jones and others, 1996; Auman 

and others, 1997; Guruge and others, 2001b). The latter value 

suggests that population-level effects could exist. This is of 

even greater concern because concentrations of PCBs and 

DDE in adult black-footed albatrosses have increased over the 

past decade (Finkelstein and others, 2006).

4

Hazard Index (HI) is the Toxic equivalent (TEQ) divided by the No 

Observable Adverse Effect Level (NOAEL). At HI=1 NOAEL has been 

reached, at HI=10 the first signs of adverse effects appear, and at HI=20 

population-level effects are observed (Auman and others, 1997).
Threats 19

 Compound

Organochlorine concentration, 

in nanogram per gram, wet weight

December 

19691

November/

December 

19932,3

1997–984,5

Subcutaneous Fat

DDD 500 

(60–940)

 54 5

(16–33)

DDT 940 

(440–1,960)

6,700 5

(3,200–9,500)

DDE 3,600 

(1,800–4,800)

6,100 5

(2,800–8,000)

PCBs 8,200 

(940–16,700)

2

2,110 21,000 5

(9,800–33,000)

PCB-TEQs 2

0.333 

Total TEQs 2

0.531 2.7 4

(2.1–3.5)

Whole Egg

DDE 3

300 

PCBs 2

199 (177–220) 3

1,000

PCB-TEQs 0.031 2,3(0.0302–0.0312)

Total TEQs 0.051 2,3(0.0484–0.0517)

0.27 4

(0.21–0.35)

1

 Fisher (1973): from Midway (n = 22). 

2

 Jones and others (1996): from Midway (Adults fat tissue, n = 5; eggs, 

n = 2 groups of 10 eggs each).

3

 Auman and others (1997): from Midway (n = 2 groups of 10 eggs each).

4

 Guruge and others (2001a): from fisheries nearby Midway (n = 7).

5

 Guruge and others (2001b): same samples as Guruge and others (2001a).

Table 3. Mean and range of organochlorine concentrations in 

the subcutaneous fat of adult Laysan albatrosses and whole eggs, 

Midway Atoll.

[Compound: DDE = 1,1-dichloro-2,2’-bis-chlorophenyl-ethylene; DDT = 

dichloro-diphenyl-trichloroethane; DDD = dichloro-diphenyl-dichloroethane; 

PCBs = polychlorinated biphenyls; TEQs = 2,3,7,8-TCDD toxic equivalents; 

TCDD = 2,3,7,8-tetrachlorodibenzo-p-dioxin]

 Compound

Organochlorine concentration, 

in nanogram per gram, wet weight

December 

19691

November/

December 

19932,3

1997–984,5

Subcutaneous Fat

DDD 950 

(680–1,160)

190 5

(73–610)

DDT 3,500 

(970–7,580)

33,000 5

(15,000–76,000)

PCBs 22,300 

(15,000–34,400)

92,000 5

(36,000–180,000)

DDE 15,300 

(5,100–22,700)

30,200 5

(13,000–73,000)

TEQs 6.0 4

(2.9–9.9)

Whole Egg

DDE 3

1,800

PCBs 2

688, 33,800

PCB-TEQs 2,30.087

Total TEQs 2,30.124 0.60 4

(0.29–0.99)

1

 Fisher (1973): from Midway (n = 7).

2

 Jones and others (1996): from Midway (n = 1 group of 10 eggs).

3

 Auman and others (1997): from Midway (n = 1 group of 10 eggs).

4

 Guruge and others (2001a): from fisheries nearby Midway (n = 16).

5

 Guruge and others (2001b): same samples as Guruge and others (2001a).

Table 4. Mean and range of organochlorine concentrations in 

subcutaneous fat of adult black-footed albatrosses and whole 

eggs, Midway Atoll.

[Compound: DDD = dichloro-diphenyl-dichloroethane; DDT = dichlorodiphenyl-trichloroethane; PCBs = polychlorinated biphenyls; DDE = 

1,1-dichloro-2,2’-bis-chlorophenyl-ethylene; TEQs = 2,3,7,8-TCDD toxic 

equivalents; TCDD = 2,3,7,8-tetrachlorodibenzo-p-dioxin]

Egg shells of black-footed albatrosses collected in 1995 

were 3–4 percent thinner than eggs collected before WWII 

(Ludwig and others, 1998). Fisher (1973) also reported that 

eggshells thinned between 1959 and 1969. Although the 

average concentration of DDE in eggs is below the threshold 

for eggshell thinning, variation is high and Ludwig and others 

(1998) estimated that 2–3 percent of the female population 

contain concentrations of DDE that produce eggshell thinning, 

and therefore loss by crushing. The percentage of black-footed 

albatross eggs lost due to shell breakage during the first week 

of incubation in 1994 was 3.34–4.02 percent compared to 

1.54–1.65 percent for Laysan albatrosses (Ludwig and others, 

1998). Broken eggs were crushed at the pointed end and 

broken egg shells were 40 percent thinner than intact eggs.

The higher concentration of organochlorines in blackfooted albatrosses, relative to Laysan albatrosses, is thought 

to reflect geographic differences in foraging areas, rather than 

dietary differences (Finkelstein and others, 2006). Blackfooted albatrosses consume more flying fish eggs than Laysan 

albatrosses, a food that adsorbs lipophilic contaminants 

from the sea surface (Ludwig and others, 1998). However, 

dietary preferences are not different enough to explain why 

organochlorine concentrations are about 400 percent higher 

in black-footed albatrosses than Laysan albatrosses. This may 

be the result of different foraging ranges of adults during the 

breeding season (Fernández and others, 2001), exposing each 

species to different risk levels (Finkelstein and others, 2006). 
20 Status Assessment of Laysan and Black-Footed Albatrosses, North Pacific Ocean, 1923–2005

Black-footed albatrosses frequent the northeastern Pacific, 

an area known to have high concentrations of organochlorine 

contaminants in contrast to Laysan albatrosses that typically 

feed farther west in the North Pacific Ocean, a region having 

lower contaminant concentrations (Guruge and others, 2001a, 

2001b).

Organochlorine concentrations in both species are likely 

having subtle effects on individual birds and increases could 

potentially have population-level effects (Auman and others, 

1997). The primary source of DDT in the North Pacific Ocean 

may be agriculture application in Southeast Asia (Ludwig 

and others, 1998), whereas PCBs are derived from industrial 

practices (Finkelstein and others, 2006).

Plastics

Laysan albatrosses at Midway Atoll have a higher 

prevalence, diversity, and volume of plastic in their stomachs 

than other Hawaiian seabirds (Kenyon and Kridler, 1969; 

Sileo and others, 1990b). Adults ingest the plastic at sea 

and then feed it to their chicks (Kenyon and Kridler, 1969; 

Pettit and others, 1981). Plastic and other indigestible items 

(such as squid beaks) are accumulated in the upper stomach, 

or proventriculus, during chick rearing, but usually are 

regurgitated by the chick prior to fledging (Pettit and others, 

1981; Sievert and Sileo, 1993). Although the incidence and 

total amount of plastic are higher in chicks that die prior to 

fledging, the overall effect of plastic ingestion is uncertain 

(Fry and others, 1987; Auman and others, 1998). A direct 

relation between chick death and plastic ingestion occurs 

only when large amounts of plastic (greater than 150 g) 

appear to cause impaction (Fry and others, 1987). Sievert and 

Sileo (1993) concluded that mortality directly attributable 

to ingested plastic was not a significant cause of death in 

albatross chicks.

Plastic ingestion could reduce a chick’s ability to swallow 

full-size meals, resulting in under-nourishment and possibly 

dehydration. Laysan albatross chicks with ‘large’ volumes 

(greater than 22 cm3

) of plastic in their proventriculus attained 

significantly lower asymptotic fledging weights than chicks 

with small amounts (less than 22 cm3) of plastic (Sievert and 

Sileo, 1993; Auman and others, 1998). Sub-lethal, ‘large’ 

volumes of plastic were found in 27 percent of Laysan and 

16 percent of black-footed albatross chicks, but no effects on 

growth were detected for black-footed albatrosses (Sievert 

and Sileo, 1993). Dehydration was the most common cause 

of death in older Laysan albatross chicks at Midway Atoll, 

coincident with higher temperatures in May to July (Sileo and 

others, 1990a; Sievert and Sileo, 1993). Because this effect 

occurs near the end of chick rearing and only one in four 

chicks contain high plastic levels, the overall effect of plastic 

ingestion may be to reduce chick survival to fledging by 

0.0–5.7 percent (Sievert and Sileo, 1993) or 0.2–1.0 percent 

(Sileo and others, 1990a) in some years.

Black-footed albatross chicks also had a high incidence 

and diversity of plastic in their proventriculus (Sileo and 

others, 1990b). Although the incidence and abundance of 

plastics were usually lower than in Laysan albatrosses (Sievert 

and Sileo, 1993; Gould and others, 1997), black-footed 

albatrosses contained higher amounts of plastic fiber, probably 

derived from fishing gear (Sileo and others, 1990b; Gould and 

others, 1997). 

Plastic ingestion also may increase the absorption of 

organochlorine compounds (Fry and others, 1987), as these are 

positively adsorbed on plastic surfaces (Carpenter and others, 

1972). However, the amount of organochlorines, as PCBs, 

accounted for by plastic particles seems to be small relative to 

trophic accumulation (Ryan and others, 1988).

Disease

Avian pox is a viral disease, transmitted by mosquitoes, 

that affects albatross chicks on Midway Atoll and the main 

Hawaiian Islands. Mosquitoes are not native to Hawai`i and 

pox has not been observed at the other NWHI colonies, where 

mosquitoes have not been introduced. Although pox was once 

thought to be a serious threat to Laysan albatrosses at Midway 

Atoll, and epizootics with extensive chick mortality have 

occurred irregularly in the past (Sileo and others, 1990a), it is 

now known that most of the infected chicks survive (Young 

and VanderWerf, 2008). Pox rarely affects black-footed 

albatross chicks; possibly because they nest in more open 

areas where mosquito numbers are lower. The vulnerability of 

albatrosses to West Nile Virus and avian influenza is unknown.

 Mild infections of chiggers (Womersia midwayensis) 

and some associated mortality were documented in Laysan 

albatross chicks at Midway Atoll in 1987, and an outbreak 

of mites apparently resulted in increased mortality of blackfooted albatross chicks at Kure Atoll in 2002 and 2003 

(C. Vanderlip and A. Marie, Hawai`i Department of Land and 

Natural Resources, unpub. data, 2004).

Dehydration was the most prevalent cause of death in 

older Laysan albatross chicks during a study at Midway Island 

in 1987 and was suspected to be one of the important causes of 

recurrent fledgling epizootics at Midway and Laysan Islands 

(Sileo and others, 1990a). This result was further supported 

in 1993–95, when, as a result of dehydration, many Laysan 

albatross chicks on Midway Island died from necrotizing 

enteritis (Work and others, 1998).

Population Size and Isolation

The current population size of black-footed albatross is in 

the hundreds of thousands and Laysan albatross number in the 

millions, thus, no demographic problems due to environmental 

stochasticity or genetic drift are expected. Genetic diversity 

of Hawaiian black-footed albatrosses is in correspondence 
Monitoring and Management Activities 21

with its population size (Walsh and Edwards, 2005). The 

overwhelming majority of both species nest on six low atolls/

islands in the Hawaiian archipelago. This concentration of 

birds at a small number of locations may make the populations 

vulnerable to catastrophic events. 

Climate Change

Predicted sea-level rise associated with global climate 

change poses a significant threat to the low-lying islands 

of the NWHI and the central Pacific (Baker and others, 

2006). Black-footed albatrosses may be affected sooner than 

Laysan albatrosses, because they nest on open, sandy beaches 

around the periphery of these islands, and strong storms and 

associated storm surges can cause significant nest loss (Fisher, 

1971b; McDermond and Morgan, 1993). However, loss of 

habitat to erosion will affect both species. When sea levels 

rose in the past, it was assumed that species moved to higher 

islands as the low islands disappeared, but current human 

occupation and introduced predators on the main Hawaiian 

Islands limit options for new, viable colony sites (Baker and 

others, 2006). As sea levels rise over the next century, secure 

habitat on higher islands throughout the range will become 

increasingly important.

Increased sea surface temperatures could result in 

changes in the location and intensity of typhoons in the central 

Pacific, causing them to form farther east and affecting islands 

and atolls that are usually unaffected (Spennemann, 1998). 

It is difficult to predict the effects that large-scale changes in 

the marine ecosystem (for example, disruption of currents, 

acidification, changes to food webs and food distribution) will 

have on albatrosses.

Monitoring and Management Activities

Monitoring 

Breeding Surveys

Counts and estimates of active nests have been conducted 

using standardized techniques at French Frigate Shoals, 

Laysan Island, and Midway Atoll since 1980, 1992, and 

1992, respectively (Flint, 2005). Surveys of both species 

have been conducted annually at French Frigate Shoals and 

Laysan Island. At Midway Atoll, black-footed albatrosses 

have been surveyed annually since 1992 and six censuses of 

Laysan albatrosses have been conducted between 1992 and 

2005; counts of Laysan albatrosses have not been conducted 

annually at Midway Atoll because of the high cost of counting 

this large colony.

Standardized surveys are conducted early during the 

incubation period after most eggs have been laid and prior 

to any significant nest failure. Counts typically are initiated 

mid-December and completed by the first week of January. 

At Laysan Island, the number of Laysan albatross nests is 

estimated from counts of plots along transect lines rather than 

direct counts of all nests. From 1992 to 2005, black-footed 

albatross nests at Laysan Island were estimated from the same 

standardized transects, but the sampling variance associated 

with these estimates was quite large, and direct counts have 

been conducted since 1998. There are earlier population 

counts and estimates for all three islands, but methods varied. 

 Surveys at these three colonies provide an estimate 

of active nests for greater than 75 percent of the World’s 

population of black-footed albatrosses and greater than 

90 percent of Laysan albatrosses. At other islands in the 

NWHI, where USFWS does not maintain permanent or 

seasonal staff during the winter, surveys are opportunistic and 

usually obtained during the spring or summer months. These 

counts are adjusted to account for egg and chick loss prior to 

the count. These surveys provide an estimate of the number of 

active nests (breeding pairs) in a given year and do not include 

adult birds that do not lay an egg or birds that have not yet 

reached breeding age.

USFWS contracted with the U.S. Geological Survey 

(USGS) Patuxent Wildlife Research Center to review 

the albatross monitoring program. USGS recommended 

a demographic monitoring program based on mark and 

recapture of banded adult birds (W.L. Kendall, U.S. 

Geological Survey Patuxent Wildlife Research Center, written 

commun., 2005). This program was implemented at Midway 

Atoll, French Frigate Shoals, and Kilauea Point, Kaua`i 

during the 2005–06 breeding season and at Laysan Island in 

2006–07. This new program will provide information on adult 

survival, probability of a breeder skipping a breeding season, 

and reproductive success. It will be evaluated and documented 

over a 3-year period, and if successful, it will be implemented 

as the long-term population monitoring program for these 

two species in the Hawaiian Islands. Counts of active nests at 

Midway Atoll, Laysan Island, and French Frigate Shoals will 

continue, but the frequency of these counts may change.

As part of this collaboration, USGS compiled all existing 

albatross banding and recapture data from the past 50 years 

into a database that is administered by the USGS Bird Banding 

Lab (Doherty and others, 2006). Preliminary evaluations of 

survival and recruitment rates for black-footed and Laysan 

albatrosses were conducted, but overall data quality was not 

sufficient to support rigorous analysis (W.L. Kendall, U.S. 

Geological Survey Patuxent Wildlife Research Center, written 

commun., 2005).
22 Status Assessment of Laysan and Black-Footed Albatrosses, North Pacific Ocean, 1923–2005

Bycatch Monitoring

Numerous analyses indicate that fishing bycatch is the 

most important source of human-induced mortality for both 

albatross species. In recent years, the U.S. and Canada have 

implemented scientific observer programs to monitor bycatch 

(including seabird bycatch) of some fisheries that operate out 

of Hawai`i and along the west coast of North America (Alaska 

to California). But not all fleets are monitored and most 

International pelagic longline fleets (Japan, Korea, Russia, 

and China) are not monitored (Cousins and Cooper, 2000). 

Many of the fleets that are monitored use mitigation measures 

to minimize the bycatch of seabirds; the unmonitored fleets 

generally are not required to use mitigation measures, so 

estimation of bycatch is even more difficult. Collection 

and analysis of albatross carcasses salvaged from fisheries 

provide important information on age or sex biases in bycatch 

mortality, but few fisheries salvage dead birds.

Management Activities

Protection of Nesting Islands

United States.—The NWHI support greater than 

99 percent of the World’s nesting Laysan albatrosses 

and greater than 95 percent of the World’s black-footed 

albatrosses. The first legal protection of these islands came in 

1903 when President Theodore Roosevelt issued Executive 

Order 199A placing Midway Atoll under the control of the 

U.S. Navy in response to recurring reports of squatters and 

poachers killing large numbers of birds. The rest of the NWHI, 

including the marine habitat surrounding the islands from 

Nihoa to Kure (excluding Midway), gained legal protection 

in 1909, when Roosevelt established the Hawaiian Islands 

Bird Reservation (Executive Order 1019). The name was 

changed to the Hawaiian Islands National Wildlife Refuge in 

1940. Although plume hunters and others continued to exploit 

albatross in the NWHI after designation of the Reservation, 

this protection spared these colonies from total extirpation, 

which was the fate of other colonies throughout the range. 

Midway Atoll was designated a National Wildlife Refuge in 

1988, while still under U.S. Navy administration. In 1996, 

Midway Naval Air Station was closed and administration of 

the atoll and surrounding reefs was transferred to the USFWS 

(Executive Order 13022). Kure Atoll, originally part of the 

Hawaiian Islands Bird Reservation, was commissioned a 

LORAN Station in 1961 and was administered by the U.S. 

Coast Guard until 1992 when it was transferred to the State of 

Hawai`i, to be managed by the Hawai`i Department of Land 

and Natural Resources as a State Seabird Sanctuary. All other 

islands of the NWHI are managed by the USFWS as National 

Wildlife Refuges (U.S. Fish and Wildlife Service, 2005). In 

2006, approximately 139,793 mi2

 of emergent and submerged 

lands and waters of the NWHI, including the National Wildlife 

Refuges and State Seabird Sanctuary, were included in the 

Papahānaumokuākea Marine National Monument (Presidential 

Proclamation 8031).

Japan.—The Izu and Ogasawara Islands are in Japan’s 

National Park system. Albatross breeding islands in the 

Ogasawara (Bonin) Islands and Torishima in the Izu Islands 

are designated as Special Protection Areas in which wildlife 

capture is prohibited. The Senkaku Retto, a breeding site of 

disputed national ownership (Japan, China, and Taiwan), has 

no legal protection.

Mexico.—Guadalupe Island and the Revillagigedos 

Islands are Biosphere Reserves, administered by the Comisión 

Nacional de Áreas Naturales Protegidas (CONANP).

Habitat and Vegetation Management

Habitat restoration at former military bases is ongoing at 

French Frigate Shoals, and Midway, Kure, and Johnston atolls. 

The Department of Defense worked with the State of Hawai`i 

(Kure Atoll) and USFWS to restore habitat when the bases 

were decommissioned and transferred to the wildlife agencies. 

USFWS and the State of Hawai`i have continued habitat 

management efforts at these atolls, which includes removal 

and modification of remaining structures that negatively affect 

albatrosses (for example, removal of light poles and excess 

buildings, control and removal of invasive vegetation, and rat 

eradication).

Lead poisoning of albatross chicks remains a problem at 

Midway Atoll, where chicks eat lead-based paint chips peeling 

from old buildings. USFWS attempted to reduce this problem 

by covering areas around the most highly contaminated 

buildings with ground cloth, but this has not proven 

successful. Other means of addressing the problem need to be 

devised and implemented.

Control programs for the invasive weed, golden crownbeard, have been implemented at Kure and Midway Atolls, 

but they are very costly, labor intensive, and of limited 

success. New methods to eradicate or control this invasive 

plant are needed. USFWS also has a rigorous program to 

preclude the transfer of exotic plants or insects from highly 

contaminated islands, such as Midway Atoll, to the rest of the 

NWHI. Restrictions regarding the treatment of food, clothing, 

camping gear, and other equipment are strictly enforced when 

moving between islands. 

At Midway Atoll, several of the highest density nesting 

areas are dominated by introduced grasses that must be 

mowed annually to keep the vegetation low. If left unmanaged, 

the vegetation grows too high, and albatross nest densities 

decrease. Recent introduction of endangered Laysan ducks 

and recovery of Bonin petrel populations at Midway Atoll may 

complicate management of these areas in the future.
Population Status and Trends 23

Predator Management

Introduced terrestrial predators are no longer an issue 

at colonies in the NWHI, as all non-native predators have 

been removed. Predator control actions are necessary at the 

main Hawaiian Island colonies, and coordinated efforts are 

ongoing by Hawai`i Division of Forestry and Wildlife, U.S. 

Department of Agriculture–Wildlife Services, and USFWS. 

Likewise, control programs have been implemented at some of 

the Mexican colonies by Grupo de Ecologia y Conservacion 

de Islas, Island Conservation, and SEMARNAT. A cat 

eradication program was recently completed at Wake Atoll, 

and a follow-up evaluation is scheduled. Rats remain an issue 

at this site.

Fishery Management

Management to reduce albatross bycatch in North 

Pacific fisheries is complicated because many different 

nations participate in these fisheries. Regulations to reduce 

the incidental take of seabirds, specifically albatrosses, 

in commercial fishing operations have been promulgated 

for several fisheries that operate out of Hawai`i, Alaska, 

Washington, Oregon, and California. However, three different 

Fisheries Management Councils function in the Pacific and 

in some instances, the regulations for comparable fisheries, 

operating in the same general area, are not consistent (for 

example, the shallow-set pelagic longline fisheries for 

swordfish that operated out of California versus Hawai`i from 

2001 to 2005). This is most often an issue with U.S. pelagic 

fisheries that operate on the high seas. Other nations that 

operate pelagic longline fisheries in the North Pacific typically 

do not require the use of mitigation measures to reduce the 

bycatch of seabirds and do not have observers to monitor the 

magnitude and composition of the seabird bycatch. 

International pelagic longline fleets, targeting swordfish 

and tuna in the North Pacific, currently pose the greatest 

known threat. The fleets fishing in the area of overlap with 

Laysan and black-footed albatrosses primarily are vessels 

from Japan, Taiwan, Russia, and the U.S., although vessels 

from China and Korea may overlap with the southern portion 

of the albatrosses’ range. The U.S. Hawaii-based fleet has 

required the use of seabird mitigation measures since 2000, 

and this has resulted in a significant reduction in the bycatch 

of albatrosses by this fleet. Use of mitigation measures was 

not required in the U.S. West Coast-based tuna and swordfish 

fleet (fishing west of 150o W longitude) prior to closure of the 

swordfish fishery in 2004. Seabird mitigation measures are 

now required for all vessels fishing with longline gear off the 

U.S. West Coast under the Highly Migratory Species Fishery 

Management Plan.

Albatross bycatch also occurs in demersal longline 

fisheries in the North Pacific. The U.S. has required the use 

of mitigation measures by most of the vessels in Alaska’s 

demersal longline fisheries since 1997, and albatross bycatch 

has been greatly reduced. Canada has required the use of 

seabird avoidance measures since 2002, as a condition of 

licensing in the longline fisheries off British Columbia. 

Seabird mitigation measures are not required in the demersal 

longline fisheries that operate off California, Oregon, and 

Washington. Russia and Japan also have demersal longline 

fleets in the North Pacific. U.S. scientists are collaborating 

with Russian scientists to assist in the development of 

mitigation measures for Russian longline fisheries.

The U.S. has had some level of scientific observer 

coverage and regulations to mitigate seabird bycatch in its 

pelagic longline fishery since 1993. Despite the relatively high 

level of albatross bycatch in pelagic longline fisheries, only 

the total fishing effort and fish catch are known for the other 

International fleets operating in the North Pacific. As of 2005, 

data from the U.S. observer programs were the only detailed 

information available for this fishery.

Migratory Bird Treaty Act

The Migratory Bird Treaty Act (MBTA) is the U.S. 

domestic law that implements four International conventions 

(with Canada, Mexico, Japan and Russia) for the protection 

of shared migratory bird resources. Under the MBTA, it is 

unlawful to take, capture, kill, or possess any migratory bird, 

including albatrosses, unless permitted by regulation. The 

MBTA is not enforced beyond 3 nautical miles from the U.S. 

coastline. However, many activities that incidentally kill 

albatross, such as fishery bycatch, occur beyond the 3-mile 

limit.

Population Status and Trends 

Understanding population trends for long-lived species is 

often complicated by delayed age at first breeding, propensity 

to skip breeding in a given year, environmental variability, 

lack of information on juveniles, limited understanding of 

albatross autecology, and lack of continuous population data. 

As a consequence, population projections from models based 

on the best available data are the primary means of assessing a 

species’ conservation status. 

Assessing the conservation status of a species is based on 

at least two components: (1) describing the population trend 

by fitting a model to the data, and (2) projecting population 

changes over a specified time interval given an initial 

population size (population viability analyses, or PVA). 

An assessment of both albatross species was conducted 

by applying three different analyses to the breeding population 

estimates: (1) regression analysis, using the combined counts 

from Midway Atoll, Laysan Island, and French Frigate Shoals; 

(2) population viability analysis, using the counts from each of 

these three colonies since 1980; and (3) age-structured matrix 

modeling, based on a long-term breeding population data set.
24 Status Assessment of Laysan and Black-Footed Albatrosses, North Pacific Ocean, 1923–2005

Population Analysis Methods

All analyses were based on estimates or counts of active 

nests at French Frigate Shoals, Laysan Island, and Midway 

Atoll. Regression analysis was used to evaluate linear trends 

in populations over 1923–2005, 1957–2005, and 1992–2005. 

Population viability analyses were conducted by fitting 

stochastic, discrete-time, logistic, and exponential models 

to observed data, and then making population projections 

60 years into the future. Age-structured population models, 

based on a matrix modeling framework, were used to evaluate 

the effect of fishery bycatch on populations, and estimates 

were made of the maximum number of mortalities, not 

including natural deaths, that could occur while maintaining 

an optimum sustainable population (Potential Biological 

Removal, or PBR). Estimates of albatross bycatch were 

obtained either by projecting measured rates for U.S. fisheries 

to unmonitored fleets, including International fleets, or from 

published values. Detailed descriptions of analytical methods 

are provided in appendix C.

Results for Laysan Albatross

Population Estimates – A Historical Review

Albatross populations were exploited in the late 1800s 

and early 1900s for feathers, eggs, and guano extraction, 

resulting in significant decreases in population and the 

extirpation of numerous colonies (Rice and Kenyon, 1962a; 

Spennemann, 1998). Records prior to feather hunting are 

sparse, and reports of colony size for the large colonies are 

often disputed, but estimates for Laysan Island alone were 

as high as 2 million birds (Schlemmer in Nutting, 1904). 

The population increased following the cessation of feather 

hunting. From the 1920s to 2005, the total number of nesting 

pairs increased from an estimated 17,930 to 600,000 (table 5). 

Some islands may now support colonies that are larger than 

pre-feather hunting levels (Midway and Kure Atolls) although 

other islands likely support smaller colonies (Laysan and 

Wake Islands). Colonies on several islands in the central and 

western Pacific never reestablished following extirpation 

(Johnston Atoll, Minami Torishima, and Torishima in the 

Izu Islands). Population growth generally has been highly 

variable between colonies (table 5, fig. 5). Below, we present 

a summary of Laysan albatross population changes at each 

colony, beginning with the northernmost colony in the NWHI.

Figure 5. Number of Laysan albatross breeding pairs 

at colonies from the 1920s until 2005. Values are shown 

in table 5.

tac_08_9354_0255_Albatrosses_Fig05

0

50,000

100,000

150,000

200,000

250,000

300,000

350,000

400,000

450,000

Kure Atoll

Midway Atoll

Pearl and 

Hermes Reef

Lisianski Island

Laysan Island

Gardner 

Pinnacles

French Frigate

Shoals 

Necker Island

Nihoa Island

 Ni`ihau Island

 Ka’ula Island

Kaua`i Island

 O`ahu Island

JAPAN

MEXICO

NUMBER OF BREEDING PAIRS

0

5,000

10,000

15,000

20,000

25,000

30,000

A. Breeding pair estimates from each island. 

B. Breeding pair estimates at all islands except Midway Atoll and 

 Laysan Island. Kure Atoll Midway Atoll Pearl and Hermes Reef Lisianski Island

Laysan Island

Gardner 

Pinnacles

French Frigate

Shoals 

Necker Island

 Nihoa Island

Ni`ihau Island

Ka’ula Island

 Kaua`i Island

O`ahu Island

JAPAN

MEXICO

1920s

1957–58

2002–05

1920s

1957–58

2002–05
Population Status and Trends 25

Laysan albatross colony on Laysan Island in the 1890s. 

Photograph courtesy of Bishop Museum, Honolulu, Hawai`i (http://www.bishopmuseum.org)
26 Status Assessment of Laysan and Black-Footed Albatrosses, North Pacific Ocean, 1923–2005

Colony

Estimated number of albatross breeding pairs

Hatch years

19231

* 1957–58 1981–2005

U.S.A

Kure Atoll 75 2350 3*3,900 (2000)

Midway Atoll 3,800 2

100,055 3408,130 (2005)

Pearl and Hermes Reef 830 2

17,750 3*6,910 (2003)

Lisianski Island 1,270 4

*<6,000 (1960s) 326,500 (1982)

Laysan Island 10,800 2

130,000 3140,860 (2005)

Gardner Pinnacles 3 2

2 515 (?)

French Frigate Shoals 200 2

584 33,230 (2005)

Necker Island 950 2

2,500 3*500 (1995)

Nihoa 3 6

*<50 

(1960s)

3

0 (1995)

Ni`ihau 2

500 3190 (2002)

Ka`ula 0 2

0 360 (1981)

Kaua`i 7

1 (1945) 3160 (2005)

O`ahu 2

0 853 (2005)

Japan

Ogasawara Gunto 

(Bonin Island)

 920 (2005)

Mexico

Guadalupe Island 10337 (2005)

Revillagigedo Island 11, 1263 (2003)

Alijos Rocks 113 (2003)

Total (rounded) 17,930 257,800 600,000

1

Wetmore in Rice and Kenyon (1962a).

2

Rice and Kenyon (1962a).

3

Flint (2005).

4

Clapp and Wirtz (1975).

5

Gales (1998).

6

Clapp and others (1977).

7

Munro (1945) in Tickell (2000).

8

Young and others (in press).

9

Chiba and others (2007).

10

R.W. Henry, University of California, Santa Cruz, written commun., 2008.

11

Pitman and others, 2004.

12

R. Wanless, BirdLife South Africa, written commun., 2009.

*spring/summer estimates were adjusted for nest loss.

Table 5. Estimates of the number of Laysan albatross breeding pairs 

by colony and hatch year at all extant colonies.

[Hatch year of census is shown in parentheses]

Kure Atoll.—Wetmore reported 50 pairs of 

Laysan albatrosses in the spring of 1923 (Olson, 

1996). By 1958, the nesting population had increased 

to 350 pairs (Rice and Kenyon, 1962a). As a result 

of habitat modifications, Laysan albatross numbers 

increased to 1,450 pairs in 1963 (Rice and Kenyon, 

1962a; Robbins, 1966). Following closure of the 

LORAN Station, the population increased to 3,900 

pairs in 2000 (Hawai`i Department of Land and 

Natural Resources, unpub. data, 2000). 

Midway Atoll.—Before human occupation, 

Midway Atoll probably supported several thousand 

nesting pairs of Laysan albatrosses (Munro, 1942, 

in Rice and Kenyon, 1962a). Habitat modifications 

by the Pacific Cable Company led to a rapid 

population increase (Rice and Kenyon, 1962a). 

Wetmore (1923) reported more than 1,500 pairs on 

Eastern Island and 1,000 pairs on Sand Island “all 

with well grown young” (Wetmore in Olson, 1996). 

Military activities during WWII (1941–45), and 

albatross “control programs” (1955–65), resulted 

in population decreases during these periods. The 

breeding population continued to decrease from 

approximately 100,000 pairs in 1956 to 72,000 pairs 

in 1962 (Robbins, 1966). After discontinuation of 

the Distant Early Warning Line radar base in 1965, a 

second period of rapid population growth began, and 

408,000 active nests were counted in December 2005 

(figs. 5 and 6). Over the period from 1923 to 1958, 

the population growth rate (λ) averaged 1.105, and 

decreased to 1.031 from 1958 to 2005. During the 

past 15 years, breeding pairs of Laysan albatrosses 

appear to have remained relatively stable, although 

annual variation in counts has been considerable 

(fig. 6). 

Pearl and Hermes Reef.—There are no 

quantitative estimates of albatross populations at 

this atoll prior to feather hunting. From the 1920s to 

1958, the Laysan albatross population increased from 

an estimated 830 to 17,750 pairs, probably a result 

of rabbit eradication in 1928 and the ending of feather 

hunting (Amerson and others, 1974). An estimate 

of 12,840 young in late March 1968 (Amerson and 

others, 1974) indicated that the population remained 

relatively high at least through the 1960s, before 

decreasing to approximately 6,900 pairs in 2003 

(table 5). Vegetation on Southeast Island, where 

most albatrosses nest, changed from grasses and 

forbs in 1958 (Rice and Kenyon, 1962a) to a 

community currently dominated by the invasive, 

golden crown-beard.
Population Status and Trends 27

tac_08_9354_0255_Albatrosses_Fig06

Total

Tern

East

Trig

Whale-Skate

Gin

Lt.Gin

NUMBER OF BREEDING PAIRS

0

0

50,000

100,000

150,000

200,000

250,000

500

1,000

1,500

2,000

2,500

3,000

3,500

0

100,000

200,000

300,000

400,000

500,000

450,000

350,000

250,000

150,000

50,000

1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005

Laysan Island

French Frigate Shoals

Midway Atoll

Figure 6. Number of breeding pairs of Laysan albatross on Midway Atoll, Laysan Island, and French Frigate Shoals, 1958–

2005. The colony and the source of data for the 1950s and 1960s were: Midway—Rice and Kenyon (1962a), Robbins (1966), 

Ludwig and others (1979, in Tickell, 2000); Laysan—Rice and Kenyon (1962a), Ely and Clapp (1973); French Frigate Shoals—

Rice and Kenyon (1962a), Amerson (1971). Data for 1979–2005 were collected by U.S. Fish and Wildlife Service personnel.
28 Status Assessment of Laysan and Black-Footed Albatrosses, North Pacific Ocean, 1923–2005

Lisianski Island.—In 1891, Laysan albatrosses were 

considered abundant on the island but no quantitative 

estimates of the breeding population were made (Munro, 

1942, in Rice and Kenyon, 1962a). Following feather raids 

and loss of vegetation to rabbits, there were no more than 800 

pairs by late season 1923 (Wetmore in Olson, 1996). Rice and 

Kenyon (1962a) estimated 30,000 pairs in 1958, but Clapp and 

Wirtz (1975) felt this estimate was high and estimated that the 

breeding population pairs in the 1960s were usually 4,000 to 

5,000 pairs. By 1982, the population increased to an estimated 

26,500 pairs (U.S. Fish and Wildlife Service, unpub. data, 

1980–2005). The population growth rate (λ) was 1.048 from 

1923 to the 1960s and 1.034 from the 1960s to 1982.

Laysan Island.—Historically, Laysan Island supported 

the largest colony of Laysan albatrosses. Estimates of colony 

size prior to feather hunting are disputed, but the earliest 

report, circa 1900, was 2 million birds (probably includes 

breeding and non-breeding birds) by the manager of the guano 

company (Nutting, 1904). Shortly after this, feather hunters 

killed hundreds of thousands of birds, primarily albatrosses, 

from 1909 to 1915 (Dill and Bryan, 1912; Ely and Clapp, 

1973). When Dill (1916) visited Laysan Island in April 1911, 

he estimated only one-sixth of the original albatross colony 

remained, numbering approximately 180,000 birds. Bailey 

(1952) considered this estimate high because he counted only 

12,300 nests the following season. However, recent surveys 

indicate that the number of breeding pairs can vary greatly 

between years, so this variation may be explainable. The 

lowest estimate of Laysan albatrosses, 6,800 pairs, was in the 

spring of 1923 when rabbits had reduced the island to a desertlike appearance (Wetmore in Ely and Clapp, 1973). From 

1923 to 1958, the albatross population rebounded, increasing 

from 10,800 to 130,000 pairs, a growth rate of 1.078 (fig. 5). 

Since 1958, the population appears to have remained relatively 

stable, although exhibiting high annual variation (fig. 6). 

Given the imprecise, early estimates, whether or not the 

colony at Laysan Island has fully recovered is difficult to 

assess.

Gardner Pinnacles.—Approximately 10 Laysan albatross 

pairs nest on these rock stacks, which have never supported a 

large breeding colony (table 5).

French Frigate Shoals.—There are no quantitative 

estimates of colony size before Wetmore’s estimate of 130 

pairs in 1923 (Rice and Kenyon, 1962a). The number of 

nesting pairs remained low through WWII and the U.S. 

Coast Guard occupation, but increased after the Coast Guard 

LORAN Station moved from East Island to Tern Island 

in 1952 (Amerson, 1971). On Tern Island, the number of 

breeding pairs remained low until the LORAN Station 

closed in 1979 and management of the island transferred 

to the USFWS. From 1958 to 1980, the number of Laysan 

albatrosses nesting on French Frigate Shoals increased from 

584 to 973 pairs, and to 3,226 pairs in 2005 (fig. 6). Both 

expansion of the land area at Tern Island and cessation of 

military activities likely contributed to this increase.

Necker Island.—An estimate of the Laysan albatross 

colony size prior to arrival of feather hunters was 1,000 to 

2,000 birds, or less than 1,000 breeding pairs (in Rice and 

Kenyon, 1962a). The colony increased in size to 2,500 pairs in 

1958, but then decreased to 500 pairs in 1995 (table 5).

Nihoa Island.—This island has never supported more 

than a small colony of Laysan albatross (maximum 20 pairs), 

and in some years, no albatross have nested here (Clapp and 

others, 1977).

Main Hawaiian Islands.—Small colonies are present 

on Ka`ula, Lehua, and Ni`ihau Islands. On Kaua`i, colonies 

are present at the Pacific Missile Range Facility on the 

west coast and various locations along the north shore from 

Kilauea Point NWR to Princeville. Colonies also are found 

on O`ahu at Ka`ena Point Natural Area Reserve, Kuaokala 

Game Management Area, and the Marine Corps Base Hawaii 

(Kaneohe Bay).

 Central Pacific Islands.— Historically, Laysan 

albatrosses nested at Johnston and Wake Atolls but these 

colonies were extirpated by feather hunters in the early 20th 

century (Rice and Kenyon, 1962a). A few pairs survived at 

Wake Atoll until the 1940s when eaten by starving soldiers 

(Spennemann, 1998). Laysan albatrosses have recently shown 

signs of recolonizing these sites. On Johnston Atoll, birds 

have been observed prospecting for nest sites (U.S. Fish and 

Wildlife Service, unpub. data, 1980–2005), and on Wake Atoll, 

a pair fledged a chick in 2002, the first Laysan albatross chick 

to fledge in more than 50 years (Rauzon and others, 2008).

Japanese Islands.—Prior to feather hunting at the turn 

of the 20th century, Laysan albatrosses nested on Minami 

Torishima (Marcus Island), in the Ogasawara (Bonin) 

Islands, and on Torishima in the Izu Islands (Bryan, 1903; 

Kurata, 1978). Of these, recolonization has only occurred 

in the Ogasawara Islands (table 5) where approximately 

10–20 pairs nest (Chiba and others, 2007). Quantitative 

estimates of historical colony sizes are not available, but 

Bryan (1903), during a 1902 survey of Minami Torishima, 

was told by feather hunters that Laysan albatrosses “had been 

so exceedingly abundant in former years that a man could kill 

three hundred birds in a day.” Although this island historically 

supported a large colony of both species, the estimate in Rice 

and Kenyon (1962a) of at least 1 million Laysan and blackfooted albatrosses nesting on this island probably is high 

(Tickell, 2000).

Mexican Islands.—The first observed breeding 

attempts of Laysan albatrosses on Mexican Islands were 

from Guadalupe Island in 1983, Clarion Island in 1987, San 

Benedicto Island in 1990, and Alijos Rocks in 2003 (Howell 

and Webb, 1992; Gallo-Reynoso and Figueroa-Carranza, 

1996; Pitman and Ballance, 2002; Pitman and others, 2004). 

Populations on these islands are growing, but numbers are 

still relatively small (approximately 400 total breeding pairs; 

R.W. Henry, University of California, Santa Cruz, written 

commun., 2008).
Population Status and Trends 29

Regression Analysis of Count Data

We used linear regression to fit lines to log-transformed 

counts of breeding pairs of Laysan albatross from Midway 

Atoll, Laysan Island, and French Frigate Shoals combined for 

1923–2005, 1957–2005, and 1992–2005 (table 6). Wetmore’s 

counts (Rice and Kenyon, 1962a; Olson, 1996) from the 

spring and summer of 1923 were adjusted for nest loss to 

generate estimates of the number of breeding pairs at each 

colony. Counts were available from all three island groups 

for 8 years (1923, 1957, 1992, 1997, 2001, 2002, 2004, and 

2005). Analyses in which the P-value was less than or equal 

to 0.05 was taken as significant (that is, evidence that the 

population had either increased or decreased over that time 

interval, table 6). Thus, over the long (83 years) and moderate 

(48 years) time intervals, the population was increasing, but 

has remained stable during the recent time period (13 years).

Population Viability Analyses (PVA) of 

Count Data

PVA were conducted for the Laysan Island and French 

Frigate Shoals populations, but insufficient data were available 

for Midway Atoll. Due to differences in demographic 

parameters for Laysan Island and French Frigate Shoals, a 

pooled PVA was not conducted.

Laysan Island.—Population estimates for Laysan 

albatrosses on Laysan Island (1992–2005) were obtained 

by re-analyzing the original transect data collected by the 

USFWS (appendix C). Results from the re-analysis produced 

lower population estimates for most years, although the 

population trend is the same as the original estimates. The 

observed growth rate distribution, Robs (fig. 7), shows 

no significant temporal trend (slope = 0.0058, t = 0.157, 

p = 0.878, USFWS original estimates), but a strong negative 

Years Statistical 

significance

Coefficient of 

determination Slope

Laysan Albatross

1923–2005 P = 0.001 R2

 = 0.85 positive

1957–2005 P = 0.032 R2

 = 0.64 positive

1992–2005 P = 0.596 R2

 = 0.08 none

Black-Footed Albatross

1923–2005 P < 0.002 R2

 = 0.74 positive

1957–2005 P = 0.785 R2

 = 0.01 none

1998–2005 P = 0.609 R2

 = 0.05 none

Table 6. Results of linear regression analyses of trends in 

Laysan and black-footed albatross populations at French Frigate 

Shoals, Laysan Island, and Midway Atoll combined.

tac_08_9354_0255_Albatrosses_Fig07

1991 1993 1995 1997 1999 2001 2003 2005

-1.0

-0.8

-0.6

-0.4

-0.2

0.0

0.2

0.4

0.6

0.8

1.0

1.2

OBSERVED GROWTH RATE DISTRIBUTION

OBSERVED GROWTH RATE DISTRIBUTION (ROBS)

0 50,000 100,000 150,000 200,000 250,000

-1.2

-1.0

-0.8

-0.6

-0.4

-0.2

0.0

0.2

0.4

0.6

0.8

1.0

1.2

BREEDING POPULATION SIZE (TIME: T-1) 

FREQUENCY

−1.5 −1.0 −0.5 0.0 0.5 1.0 1.5

0.5

1.0

1.5

2.0

-1.2

0.0

A. Frequency distribution of Robs from U.S. Fish and Wildlife 

 Service estimates. 

B. Inter-annual variability of Robs. 

C. Relation between Robs and breeding population size for U.S. Fish

 and Wildlife Service and re-analyzed data estimates.

Transects, FWS

Transects, corrected

Trendline

y = 0.0058x – 11.681

y = -7E-06x + 1.0166

R 2

 = 0.0022

R 2

 = 0.3513

Figure 7. Observed growth rate distribution (Robs) for the 

Laysan albatross breeding population, Laysan Island.
30 Status Assessment of Laysan and Black-Footed Albatrosses, North Pacific Ocean, 1923–2005

Data: 

1992–2005 

[N(Robs)=13] 

Parameters fitted 

[mean and (95-percent confidence interval)] logL(φ) AICc

Including sampling error + environmental stochasticity

Exponential 

model

ˆ = - 0.00266 (- 0.01986; 0.01469)

= 0.49684 (0.41614; 0.58242)

= 0.47975

= 0.12919

tot

env

s error

a

−







σ

σ

σ

-8.883 22.867

Logistic 

model -6 -6 -6

ˆ = 1.01202 (0.78488; 1.26352)

ˆ = 7.2621×10 (5.5818×10 ; 9.1356×10 )

ˆ = 139,357

0.41401 (0.35122; 0.47791)

= 0.39334

= 0.12919

tot

env

s error

a

b

K

σ

σ

σ −

−

 =





-5.892 20.451

Table 7. Parameter estimation for exponential and logistic R-function models fitted to 

Laysan albatross Robs data, Laysan Island.

[Laysan albatross Robs data from U.S. Fish and Wildlife Service, unpub. data, 1980–2005; Flint, 2005. 

Robs, observed growth rate distribution; aˆ, population growth rate; σtot  , total variation;

σenv  , environmental stochasticity; σs error −  , sampling error; – ˆ

b , density-dependent parameter; 

K, carrying capacity]

relation with its own population size 

(slope = -7×10-6, t = -2.441, 

p = 0.033, USFWS original 

estimates). This is a characteristic of 

populations close to their carrying 

capacity and having significant 

first-order negative feedback with 

respect to their size (Royama, 

1992; Berryman and others, 

2002). Support for the logistic 

model was indicated by a lower 

corrected Akaike’s Information 

Criterion (AICc), relative to the 

exponential model (table 7), and 

the distribution of the residuals. 

However, the logistic model did not 

fit the data significantly better than 

the exponential model (Likelihood 

Ratio Test, LRT = 1.49, p = 0.176), 

so the latter was used for population 

forecasts.

When sampling error is included 

in the exponential model, the 

population growth rate ( aˆ ) does not 

differ from zero. This is true even 

after re-estimating population sizes 

(table 8), indicating the population 

is stable and primarily affected by 

environmental stochasticity ( σenv  ). 

Analysis of the residuals indicates 

strong deviations from the general 

trend in 1999, 2000, and 2002. In 

1999, a strong, negative Robs value 

was observed, which reflects the low 

breeding population in 2000. The 

positive Robs values for 2000 and 

2002 are the result of low breeding 

population sizes in the preceding 

years.

Growth rates overlap between 

those calculated using the original 

USFWS population estimates, and 

our re-estimates. Projections using 

USFWS estimates with the sampling 

error removed, indicate a 0.50 

probability that the population will 

decrease by 7 percent (95-percent 

confidence interval [CI]: -36.2–42.6) 

in 60 years (fig. 8). Moreover, 

the low slope in the cumulative 

probability distribution (CPD) near 

the median imposes a high variance 

on this value. However, the CPD for 

Data: 

1992–2005 

[N(Robs)=13] 

Parameters fitted

[mean and (95-percent confidence limit)] logL(φ) AICc

Including sampling error + environmental stochasticity

Exponential 

model

ˆ = 0.00245 (-0.02305; 0.02876)

= 0.43078 (0.34702; 0.51384)

= 0.41410

= 0.11871

tot

env

s error

a

σ

σ

σ −







-5.820 17.140

Logistic 

model -6 -6 -6

ˆ = 0.95874 (0.71461; 1.24625)

ˆ = 7.8404×10 (5.7933×10 ; 10.2415×10 )

ˆ = 122,282

0.36263 (0.30147; 0.42585)

= 0.34265

= 0.11871

tot

env

s error

a

b

K

σ

σ

σ −

−

 =





-3.346 16.121

Table 8. Parameter estimation for exponential and logistic R-function models fitted to 

Laysan albatross Robs data after re-analysis of transect data, Laysan Island.

[Laysan albatross Robs data from U.S. Fish and Wildlife Service, unpub.data, 1980–2005; Flint, 2005. 

Robs, observed growth rate distribution; aˆ, population growth rate; σtot  , total variation; σenv  , 

environmental stochasticity; σs error −  , sampling error; – ˆ

b , density-dependent parameter; K, carrying 

capacity]

higher rates of population decline have high probabilities, as for example, the potential 

reduction of greater than 68 percent (CI: -78.9 – -53.3) has a 0.45 probability (fig. 8).
Population Status and Trends 31

tac_08_9354_0255_Albatrosses_Fig08

A.

B.

0

0.1

0.2

0.3

0.4

0.6

0.5

-1.0 -0.5 0.0 0.5 1.0

RATE OF CHANGE

CUMULATIVE PROBABILITY

0

500,000

1,000,000

1,500,000

2,000,000

TIME (YEARS)

NUMBER OF BREEDING PAIRS

2010 2020 2030 2040 2050 2060

tac_08_9354_0255_Albatrosses_Fig09

-0.80

-0.60

-0.40

-0.20

0.00

0.20

0.40

0.60

0.80

1980 1985 1990 1995 2000 2005

-0.80

-0.60

-0.40

-0.20

0.00

0.20

0.40

0.60

0.80

500 1,000 1,500 2,000 2,500 3,000

NUMBER OF BREEDING PAIRS

OBSERVED GROWTH RATE DISTRIBUTION (ROBS)

FFS trendline

Tern

FFS

Tern trendline

First-order, low noise

y = -0.0013x + 2.6897

R 2

 = 0.0009

y = -0.0002x + 0.336

R2

 = 0.1286

y = -0.0003x + 0.7356

R 2 = 0.2915

Strong perturbations

A. Inter-annual variability of Robs. 

B. Relation between Robs and the breeding population size (time: t-1). Figure 8. Population projection (A, n = 30) and 

cumulative probability (B) that a given rate of population 

change is reached over 60 years using the exponential 

model and re-analysis of transect data for Laysan 

albatross, Laysan Island.

Figure 9. Observed growth rate distribution (Robs) for 

the Laysan albatross breeding population, French Frigate 

Shoals.

The population projection using the corrected transect 

estimates of population size predicts a slightly better trend. 

After 60 years, the median population size would increase 

by 15.7 percent (CI: -20 – 63.6). But as with the previous 

analysis, there is a high probability that the population would 

decrease by greater than 50 percent (0.45 probability, mean: 

-56.6 percent, CI: -70 – -37.7, fig. 8). 

French Frigate Shoals.—The population time-series 

for French Frigate Shoals is the best available for Laysan 

albatrosses (fig. 9). The temporal trend of Robs at French 

Frigate Shoals shows no significant deviation from zero 

(slope = -0.0013, t = -0.139, p = 0.891), but a series of 

small and large vertical perturbations, characteristic of 

environmental stochasticity, affected the R-function (Royama, 

1992). As on Laysan Island, there is a significant first-order 

negative feedback with its own population size (time = t-1; 

slope = -0.0003, t = -2.939, p = 0.008). Both factors together 

suggest that this population is affected by density-dependent 

processes and is near its carrying capacity. This conclusion 

also is supported by the logistic model having a lower AICc 

value than the exponential model (table 9, fig. 10).

The exponential model suggests that the population has 

a significant positive growth rate, aˆ = 0.03837 (CI: 0.03718 – 

0.03960, after including sampling error). Analysis of the 

residuals indicates two periods of strong environmental 

perturbations. The first one occurred from 1985 to 1988, 
32 Status Assessment of Laysan and Black-Footed Albatrosses, North Pacific Ocean, 1923–2005

Data: 

1982–2005 

[N(Robs)=23] 

Parameters fitted 

[mean and (95-percent confidence interval)] logL(φ) AICc

Including sampling error + environmental stochasticity

Exponential 

model ˆ = 0.03837 (0.03718; 0.03960)

= 0.29825 (0.29125; 0.30513)

= 0.29790

= 0.01448

tot

env

s error

a

σ

σ

σ −







-4.298 13.197

Logistic 

model -4 -4 -4

ˆ = 0.73607 (0.70660; 0.76474)

ˆ = 3.1363×10 (3.0034×10 ; 3.2665×10 )

ˆ = 2,347

0.25686 (0.25195; 0.26184)

= 0.25645

= 0.01448

tot

env

s error

a

b

K

σ

σ

σ −

−

 =





-0.328 7.919

Table 9. Parameter estimation for exponential and logistic R-function models fitted to 

Laysan albatross Robs data, French Frigate Shoals.

[Laysan albatross Robs data from U.S. Fish and Wildlife Service, unpub.data, 1980–2005; Flint, 2005. 

Robs, observed growth rate distribution; aˆ, population growth rate; σtot  , total variation; σenv  , 

environmental stochasticity; σs error −  , sampling error; – ˆ

b , density-dependent parameter; K, carrying 

capacity]

when lower than usual Robs values 

occurred in 1985 and 1987 (fig. 9), 

followed by an increase in Robs as 

the population returned to a more 

typical number of breeding pairs in 

1987 and 1989 (fig. 6). The second, 

and stronger perturbation, occurred 

from 1999 to 2000 when the number 

of breeding pairs was one-half that 

of the preceding and following year 

(fig. 6).

Population projections based on 

the exponential model suggest that 

in 60 years the population has a 0.50 

probability of increasing by 8.36 

times (CI: 6.53 – 10.74), although 

there is a 0.275 probability that the 

population would decrease by 0.24 

times (CI: -0.41 – -0.04) in 60 years 

(fig. 10).

For this island, the logistic 

model presents a significant 

improvement in fitting Robs over 

the exponential model (LR test, 

LR = 13.54, p = 0.012). The logistic 

model indicates a carrying capacity 

of 2,347 Laysan albatross pairs for the entire atoll (table B-1), 

although the observed trend suggests this is an underestimate 

(fig. 6).

Matrix Model Analyses

Trend over the Past Century.—The Laysan albatross 

population grew rapidly following the end of feather hunting, 

increasing from ca. 18,000 breeding pairs in 1923 to ca. 

590,000 breeding pairs in 2005 (fig. 11). Population trends 

for individual colonies were not necessarily consistent with 

this overall pattern, and showed significant annual variation 

in number of breeding pairs. Breeding colonies on islands 

that received little human disturbance after 1923 (Pearl and 

Hermes Reef, Lisianski, Laysan, and Necker Islands) showed 

a high population growth rate until the 1950s, followed 

by stationary, although annually variable, colony sizes. In 

contrast, colonies at Midway Atoll and French Frigate Shoals, 

which were occupied by the U.S. military during and after 

WWII, exhibited a low growth rate until the 1960s. The end of 

WWII and associated military activities (for example, runway 

and base construction, habitat modification), the cessation of 

albatross control programs, and finally the decommissioning 

of military bases in the NWHI, all contributed to the high 

population growth observed at these two colonies since the 

1960s. On Kure Atoll, military occupation did not have an 

initial negative effect on the Laysan albatross colony, rather 

clearing of dense vegetation was followed by rapid growth of 

the colony (Woodward, 1972). The leveling off of colony sizes 

in the 1950s on islands that were not occupied by the military 

and colony growth on islands where humans increased nesting 

habitat support a hypothesis that nest sites may be limiting for 

Laysan albatrosses at some sites at the colony level. Further 

support for this hypothesis may be the recent colonizations 

of Mexican Islands (Howell and Webb, 1989; Pitman and 

Ballance, 2002), increasing numbers of birds breeding on the 

Main Hawaiian Islands, and the repopulation of Wake (Rauzon 

and others, 2008) and the Ogasawara Islands (Hasegawa, 

1984). However, historical estimates of colony size on Laysan 

Island far exceed current estimates, indicating that nest site 

limitation is not the only factor.

We calculated the Potential Biological Removal level, 

PBR (Wade, 1998), as a comparison for the effects of fisheries 

bycatch. In this analysis, the maximum population growth 

rate was estimated by modeling historical data on breeding 

population size using a matrix-projection model, randomly 

selected demographic parameters, and several estimates of the 

fishery bycatch rate. Demographic parameters derived using 

this approach are independent of those derived from capturerecapture analyses, and thus provide an additional approach to 

understanding population processes. 
Population Status and Trends 33

Figure 11. World Laysan albatross breeding population 

trend as derived from estimates for each island. World 

population size estimation with 95-percent CI. Nest 

site carrying capacity, K1, as the sum of the maximum 

estimated breeding pairs at each island. Fit_mean 

indicates a logistic model fitted to the estimated breeding 

population trend.

tac_08_9354_0255_Albatrosses_Fig11

100,000

0

200,000

300,000

400,000

500,000

600,000

700,000

800,000

1920 1930 1940 1950 1960 1970 1980 1990 2000

BREEDING POPULATION SIZE

EST-mean ± 1 SD

K1

Fit_mean

World population with 95-percent CI

tac_08_9354_0255_Albatrosses_Fig10

-1.0 -0.5 0.0 0.5 1.0 1.5 2.0 0

0.1

0.2

0.3

0.4

0.5

RATE OF CHANGE

CUMULATIVE PROBABILITY

0

5,000

10,000

15,000

20,000

TIME (YEARS)

NUMBER OF BREEDING PAIRS

2010 2020 2030 2040 2050 2060

A.

B.

Figure 10. Projection (A, n = 30) and cumulative probability 

(B) that a given rate of population change is reached over 

60 years using the exponential model for Laysan albatross, 

French Frigate Shoals.

Parameter Estimation.—The logistic function provided 

a good fit to the growth of the Laysan albatross population, 

suggesting a strong influence of density-dependent processes 

(fig. 11). Estimated parameters from the logistic function 

were population growth rate aˆ = 0.0673 ± 0.0031 and 

carrying capacity Kˆ = 779,144 ± 63,770 nesting pairs for the 

currently occupied islands (fig. 11). The maximum growth 

rate we estimated (7.0–7.8 percent annual) is higher than 

previous estimates for all albatross species other than the 

short-tailed albatross (6.5–8.0 percent, U.S. Fish and Wildlife 

Service, 2005). Our modeling approach indicated that simple, 

density-independent models (1) do not fit the data, and (2) 

significantly underestimate the growth rate of the population 

(table 10). Density-independent matrix models commonly 

are used in the assessment of long-lived species, despite their 

limitations for species having K-selected life-history traits 

(Bjorndal and others, 2000; Lewison and Crowder, 2003). 

Our results argue against the use of density-independent 

models when forecasting the growth of albatross populations. 

Furthermore, analysis of the population growth potential 

indicates that current low rates of growth may be primarily 

due to density-dependent processes, and secondarily to 

fisheries bycatch (fig. 12). These estimates, applicable to 

the current colonies, may change if historical colonies are 

re-established.

Adult and juvenile survival estimates derived from 

capture-recapture data differed from the estimates we obtained 

using a matrix modeling approach. Survival estimates from 

capture-recapture analyses, especially for juveniles, vary 

widely between studies indicating uncertainty in the estimates. 

Our estimates of adult survival were similar to the weighted 

adult survival estimated for 1963 to 1982 (table 11), but 

estimates for other periods differed widely from the mean 

value we obtained using our modeling approach. Capturerecapture estimates of juvenile survival were lower than our 

estimates during the period of intense military occupation at 

Midway Atoll and Tern Island (French Frigate Shoals), and 

much higher than ours afterwards (table 11). Low estimated 

juvenile survival during military occupancy, as estimated 

by capture-recapture techniques, may have resulted from 

the harassment of birds and the restriction of their nesting 

space, thus biasing the recapture rate downward. Because 

our modeling approach did not use recapture rates, it was 

unaffected by this potential bias.
34 Status Assessment of Laysan and Black-Footed Albatrosses, North Pacific Ocean, 1923–2005 Table 10. Parameter estimates [median (95-percent CI)] for the Laysan albatross population-projection matrix under different model structures. [Descriptions of parameters and models are shown in appendix C. b, constant measuring the strength of density-dependence. Lambda (λ) max, maximum growth rate of the population. NA, not applicable] Parameters Model: Exp-A Model: Exp-B Model: Log-2A Model: Log-2B Model: Log-2C Model: Log-2D Exponential: Low bycatch (mean for H1) Exponential: High bycatch (mean for H2) Logistic: Low bycatch (mean for H1) Logistic: High bycatch (mean for H2) Logistic: High bycatch (97.5 percentile for H2) Logistic; High bycatch (2.5 percentile for H2) Breeding frequency 0.76 (0.70–0.84) 0.77 (0.70–0.85) 0.77 (0.70–0.84) 0.80 (0.71–0.85) 0.78 (0.73–0.84) 0.79 (0.71–0.85) Breeding success 0.62 (0.55–0.69) 0.62 (0.56–0.69) 0.64 (0.55–0.70) 0.66 (0.57–0.70) 0.68 (0.62–0.70) 0.63 (0.56–0.69) Survival fledglings 0.775 (0.700–0.890) 0.800 (0.710–0.895) 0.810 (0.700–0.900) 0.830 (0.720–0.900) 0.880 (0.801–0.900) 0.830 (0.715–0.890) Survival juveniles 0.955 (0.942–0.985) 0.965 (0.940–0.985) 0.975 (0.945–0.990) 0.980 (0.960–0.990) 0.985 (0.973–0.990) 0.980 (0.950–0.990) Survival adults 0.955 (0.942–0.985) 0.972 (0.955–0.990) 0.980 (0.957–0.990) 0.980 (0.960–0.990) 0.985 (0.973–0.990) 0.982 (0.957–0.990)

b NA NA 1.50×10–8

(1.00×10–8 – 2.15×10–8)

1.60×10–8

(1.05×10–8 – 2.05×10–8)

1.60×10–8

(1.16×10–8 – 2.03×10–8)

1.70×10–8

(9.47×10–9 – 2.30×10–8)

Lambda (λ) max 1.054 

(1.052–1.056)

1.064

(1.062–1.066)

1.070

(1.064–1.082)

1.078

(1.072–1.088)

1.088

(1.084–1.096)

1.075

(1.066–1.087)

N 100 100 100 100 124 100

1Iteration process stopped after 21 hours.
Population Status and Trends 35

Fishery Impact.—Our 2005 estimate of fishery 

bycatch is approximately 2,500 birds per year, a value 

less than the estimated Potential Biological Removal 

level for Laysan albatrosses. Most of the fishery bycatch 

probably is accounted for by the International pelagic 

longline fleet (fig. 3), for which no official estimate is 

available. However, our model of population growth 

suggests that the long-term bycatch for the pelagic 

longline fleet was no higher than 0.187 birds/1,000 

hooks (H2 – Hypothesis 2; appendix C) Given the 

current size and growth rate for the Laysan albatross 

population, this mortality level falls below the net 

growth exhibited for the species (fig. 12), and currently 

does not appear to be threatening the long-term viability 

of the species.

Results for Black-Footed Albatross

Population Estimates – A Historical Review

Quantitative estimates of black-footed albatross 

colony sizes prior to feather hunting are even more 

limited than estimates for Laysan albatrosses. 

Populations had already been decimated by the 1920s 

when an estimated 17,800 pairs nested in Hawai`i 

and another 200 pairs nested in Japan (approximately 

18,000 pairs total; table 12). By 1958, the nesting 

population had increased to almost 55,000 pairs (Rice 

and Kenyon, 1962a), a growth rate of λ = 1.026. 

From 1958 to 2005, the population increased slowly 

to 61,700 pairs. Population changes on each island 

have varied widely (fig. 13), primarily reflecting the 

different histories of human occupation. The number of 

nesting pairs on Laysan Island and Pearl and Hermes 

Reef have decreased since 1958, but this loss has 

been compensated by increases at Kure and Midway 

Atolls, and French Frigate Shoals, where the numbers 

of nesting birds have increased since military activities 

ended. Below, we present a summary of black-footed 

albatross population changes at the current breeding 

sites.

Kure Atoll.—From 1923 to 1958, the colony size at 

Kure decreased from 365 to 70 breeding pairs (table 12), 

but the 1958 count by Rice and Kenyon (1962a) may 

have been abnormally low, since Woodward (1972) 

documented 200–350 pairs breeding annually in the 

1960s (table 12). From 1958 to 2000, the colony 

increased to an estimated 2,020 pairs, a change that was 

likely due to removal of dense vegetation in 1961 (Rice 

and Kenyon, 1962a; Woodward, 1972) and closure of 

the station in 1992.

tac_08_9354_0255_Albatrosses_Fig12

A.

B.

0.00

0.01

0.02

0.03

0.04

0.05

0.06

0.07

GROWTH RATE (R) / FISHING MORTALITY RATE

1950 1960 1970 1980 1990 2000 2010

1950 1960 1970 1980 1990 2000 2010

0

20,000

40,000

60,000

80,000

100,000

NUMBER OF ADULTS AND JUVENILES

Growth rate as r/2

EXPLANATION

Growth rate as r/4

Remaining growth potential estimate 

from breeding population size

Model log2a

Model log2d

Fishery bycatch is H1-mean

Fishery bycatch is H2-low

Fishery bycatch is H2-mean

Navy removals

Figure 12. Potential growth rate (A) and net growth (B) for the 

Laysan albatross.
36 Status Assessment of Laysan and Black-Footed Albatrosses, North Pacific Ocean, 1923–2005

Table 11. Demographic parameter estimates [mean ± 1 SD (range)] available for the Laysan 

albatross. 

[Overall estimates of the survival rates were calculated using W.L. Kendall estimates (U.S. Geological Survey 

Patuxent Wildlife Research Center, written commun., 2005) and the proportion of birds breeding at Midway 

Atoll and elsewhere, as derived from the historical breeding population reconstruction]

Parameter Kure Atoll Midway Atoll Tern Island Overall

Breeding 

frequency

 1

1960–72

0.84 ± 0.09 

(0.62–1.00)

 

Breeding 

success

2

1964–1969

0.58 ± 0.09 

(0.47–0.68)

3

1962–65

0.63 ± 0.14 

(0.49–0.78)

4

1980–2003

0.64 ± 0.19

(0.09–0.89)

 4

1992–2001 

0.50 ± 0.20

(0.22–0.76)

 

Juvenile 

survival 

rate

3

1962–72

0.982, 4–8 yr

5

1963–82

0.48 ± 0.04

5

1963–82

0.78 ± 0.17

5

1963–82

0.756

5

1983–93

1.00

5

1983–93

0.99 ± 0.001

5

1983–93

0.996

5

1994–2002

1.00

5

1994–2002

0.98 ± 0.004

5

1994–2002

0.993

Adult survival 

rate

3

1962–72

0.982, 4–8 yr

 

5

1963–82

0.48 ± 0.04

5

1963–82

0.78 ± 0.17

5

1963–82

0.756

5

1983–93

1.00

5

1983–93

0.99 ± 0.001

5

1983–93

0.996

5

1994–2002

1.00

5

1994–2002

0.98 ± 0.004

5

1994–2002

0.993

1

Fisher (1976).

2

Woodward (1972).

3

Fisher (1975a).

4

U.S. Fish and Wildlife Service, unpub. data, 1980–2005.

5

W.L. Kendall (U.S. Geological Survey Patuxent Wildlife Research Center, written commun., 2005).

Midway Atoll.—There are 

no reports of colony size prior to 

feather hunting, but during a visit 

to Midway Atoll in 1902, Bryan 

(1906) noted

“Everywhere on 

Eastern Island great 

heaps, waist high, of 

dead albatrosses were 

found. Thousands 

upon thousands of 

both species had been 

killed.”

Based on the number of carcasses, 

Bryan (1906) estimated that 

black-footed albatrosses were 

three times more abundant than 

Laysan albatrosses. The colony 

size increased rapidly from 2,000 

pairs in the 1920s to a peak of 

nearly 20,000 pairs in the early 

1940s (Fisher and Baldwin, 1946; 

Rice and Kenyon, 1962a). Fisher 

and Baldwin (1946) reported the 

black-footed albatrosses were 

not affected as much as Laysan 

albatrosses by the military 

activities associated with WWII, 

but after the war, the size of the 

colony decreased to 8,700 pairs in 

1957 (Rice and Kenyon, 1962a) 

and 4,700 pairs in 1963 (Robbins, 

1966). This decrease probably 

was due to the combined effects 

of human activities that included: 

military control programs and 

activities, introduced vegetation, 

physical alteration of the 

shoreline nesting habitat, and 

possibly fisheries bycatch (Rice 

and Kenyon, 1962a; McDermond 

and Morgan, 1993). There were 

no complete counts of breeding 

black-footed albatrosses between 

1963 and 1992. In 1992, 19,757 

nests were counted and by 2005, 

the number of nests had increased 

to 21,830. From 1999 to 2005, 

the number of nesting pairs has 

increased each year, but over the 

last 14-year period, there has been 

no detectable population trend 

(fig. 14).
Population Status and Trends 37

Colony

Estimated number of black-footed 

albatross breeding pairs

1923–32 1957–58 1994–2005

U.S.A.

Kure Atoll 1

*365 (1923) 270 3*2,020 (2000)

Midway Atoll 1

*2,430 (1923) 28,700 321,829 (2005)

Pearl and Hermes Reef 1

*3,650 (1923) 27,103 3*6,646 (2002)

Lisianski Island 1

*1,810 (1923) 22,700 3*3,737 (2002)

Laysan Island 1

*8,510 (1923) 233,523 321,006 (2005)

French Frigate Shoals 1

*730 (1923) 21,499 34,259 (2005)

Necker Island 1

*180 (1923) 2368 3*112 (1995)

Nihoa Island 1

*110 (1923) 250 3*31 (1994)

Ni`ihau (Lehua Island) 3

*10 (2002)

Ka`ula 2

100 30 (1998)

Japan

Ogasawara Gunto 3

405 (2003)

Izu Shoto 2

200 (1932) 3*1,560 (2003)

Senkaku Retto 

(Kita-kojima only)

3

*56 (2002)

Total (rounded) 18,000 54,200 61,700

1

 Wetmore in Rice and Kenyon (1962a).

2

 Rice and Kenyon (1962a). 

3

 Flint (2005).

* Spring/summer estimates were adjusted for nest loss.

Table 12. Estimates of the number of black-footed albatross 

breeding pairs by colony and hatch year. 

[The hatch year of census is shown in parentheses]

tac_08_9354_0255_Albatrosses_Fig13 NUMBER OF BREEDING PAIRS

1920s

1957–58

2002–05

1920s

1957–58

2002–05

0

5,000

10,000

15,000

20,000

25,000

30,000

35,000

JAPAN

0

1,000

2,000

3,000

4,000

5,000

6,000

7,000

8,000

Kure Atoll

Midway

Atoll

Pearl and

Hermes

Reef

Lisianski

Island

Laysan

Island

FrenchFrigate Shoals

Necker

Island

Nihoa

Island

Ni`ihau

Island

Ka’ula

Island

A. Breeding pair estimates from each island. 

B. Breeding pair estimates at all islands except Midway Atoll and 

 Laysan Island. 

JAPAN

Kure Atoll

Midway

Atoll

Pearl and

Hermes

Reef

Lisianski

Island

Laysan

Island

FrenchFrigate Shoals

Necker

Island

Nihoa

Island

Ni`ihau

Island

Ka’ula

Island

Figure 13. Number of black-footed albatross breeding 

pairs at colonies from the 1920s until 2005. Values are 

shown in table 5.

Pearl and Hermes Reef.—The colony increased from 

3,650 to 7,103 pairs from 1923 to 1958, but then decreased to 

an estimated 6,646 pairs in 2003 (table 12).

Lisianski Island.—The black-footed albatross colony 

grew from 1,810 pairs in 1923, to 2,700 pairs in 1957, and 

to 3,737 pairs in 2002 (fig. 13). Nest sites may be limiting 

because dense vegetation covers most of the island (Clapp and 

Wirtz, 1975). In addition, black-footed and Laysan albatrosses 

may compete for nest sites as indicated by both species nesting 

in open areas of the island (Clapp and Wirtz, 1975).

Laysan Island.—The earliest reports for Laysan Island 

are from Dill and Bryan (1912) who estimated 42,500 pairs 

in 1911, 1 year after the first feather raids. However, Bailey 

(1952) doubted this high figure based on his count of 7,722 

nests 2 years later. From the 1920s to 1957, estimates of 

the black-footed albatross colony increased from 4,700 to 

33,523 pairs (fig. 13; table 12). From 1992 to 2005, estimates 

of the number of nesting birds at Laysan Island were derived 

from transect samples. However, the variances associated with 

these estimates were so large that direct nest counts have been 

conducted since 1998. Direct counts indicate low interannual 

variation, and the count of 21,006 nests in 2005 is 37 percent 

less than the 1958 estimate (fig. 14).
38 Status Assessment of Laysan and Black-Footed Albatrosses, North Pacific Ocean, 1923–2005

tac_08_9354_0255_Albatrosses_Fig14

Total

Tern

East

Transects

Total

Census

Trig

Whale-Skate

Gin

Lt.Gin

NUMBER OF BREEDING PAIRS

1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005

Laysan Island

French Frigate Shoals

Midway Atoll

0

10,000

20,000

30,000

40,000

50,000

0

5,000

10,000

15,000

20,000

25,000

0

1,000

2,000

3,000

4,000

5,000

6,000

Figure 14. Number of breeding pairs of black-footed albatross on Midway, Laysan, and French Frigate Shoals from the 1950s 

to 2005. The colony and the source of data for the 1950s and 1960s were Midway — Rice and Kenyon (1962a), Robbins (1966); 

Laysan — Rice and Kenyon (1962a), Ely and Clapp (1973); French Frigate Shoals — Rice and Kenyon (1962a), Amerson (1971). 

Data for 1979 to 2005 were collected by USFWS personnel.
Population Status and Trends 39

French Frigate Shoals.—The number of breeding pairs of 

black-footed albatrosses has increased from 405 pairs in 1923 

to 4,259 pairs in 2005 (fig. 13). The overall increase primarily 

is due to increases in the number of breeding birds on East 

and Tern Islands where wash-over events due to storm surges 

are rare (Amerson, 1971). During military occupation of these 

islands, the number of breeding black-footed albatrosses 

was low. After the U.S. Coast Guard left East Island in 1952, 

the colony increased from 200 pairs in 1954 to 2,500 pairs 

in 1980 (fig. 14). Likewise, after the Tern Island LORAN 

Station closed in 1979 and administration of the atoll was 

transferred to the USFWS, the number of breeding pairs on 

Tern Island increased from 82 in 1980, to 1,721 pairs in 2003 

(fig. 14). The loss of Whale-Skate Island to erosion in 1997 

(U.S. Fish and Wildlife Service, unpub. data, 1980–2005) was 

a significant loss of nesting habitat at French Frigate Shoals. 

From 1980 to 1990, about one-third of the atoll’s black-footed 

albatross pairs nested on this islet. Only East Island supported 

a larger number of nests.

Necker and Nihoa Islands.—Only a small number of 

black-footed albatrosses nest on these small volcanic islands. 

During the past century, estimates for Necker Island fluctuated 

between 39 and 368 pairs and between 25 and 65 pairs at 

Nihoa Island. This variation may be due to annual differences 

in the proportion of pairs attempting to nest, timing of 

censuses, or true changes in the size of breeding colonies.

Japanese Islands.—Historically, black-footed albatross 

nested in the Izu Islands, Ogasawara Islands (Bonin Islands), 

Kazan Retto (Volcano Islands), Senkaku Retto, and Minami 

Torishima (Marcus Island; Tickell, 2000). Many colonies 

were extirpated by feather hunters by the early 1900s. Natural 

re-establishment of colonies occurred in the Izu Islands 

(Torishima), the Senkaku Retto, and the Ogasawara Islands 

(table 12; Hasegawa, 1984; Chiba and others, 2007). No 

quantitative estimates exist for the Japanese colonies prior to 

feather hunting, but black-footed albatrosses were reported to 

nest in large numbers on these islands. The current overall size 

of the Japanese colonies is estimated to be 2,220–2,350 pairs. 

Mariana Islands.—A colony of black-footed albatrosses 

nested on Agrihan Island in the Commonwealth of the 

Northern Marianas into the late 19th century, but was then 

extirpated and recolonization has not occurred (Jouanin, 1959 

in Rice and Kenyon, 1963; Reichel, 1991). Based on bones 

found in an archeological excavation, black-footed albatrosses 

also may have nested on Pagan Island (Tickell, 2000).

Central Pacific Islands.—Black-footed albatross were 

extirpated from Wake and Johnston atolls by feather hunters 

(Rice and Kenyon, 1962a). From 1996 to 2003, a few blackfooted albatrosses laid eggs on Wake Island, but no young 

fledged and nesting did not occur in 2004 or 2005 (Rauzon 

and others, 2008).

Mexican Islands.— The first pair of black-footed 

albatrosses nesting outside of their historic range, nested 

on Guadalupe Island in 1998, and another pair nested at 

San Benedicto Island in 2000 (Pitman and Ballance, 2002). 

Although black-footed albatrosses have visited these sites 

during subsequent breeding seasons, there have been no 

further records of nesting at either island (R.W. Henry, 

University of California, Santa Cruz, written commun., 2008).

Regression Analysis of Count Data

We used linear regression to fit lines to log-transformed 

counts of breeding pairs of black-footed albatross from 

Midway Atoll, Laysan Island, and French Frigate Shoals 

combined, for 1923–2005, 1957–2005, and 1998–2005. 

Counts were available from all three island groups for 11 years 

(1923, 1957, 1992, and 1998–2005). Analyses in which the 

P-value was less than or equal to 0.05 were taken as evidence 

that the population had either increased or decreased over the 

time interval (table 6). Thus over the longest time interval 

(83 years) the population increased, over the intermediate time 

interval (48 years), the population was stable, and there was 

no change over the shortest (13 years) and most recent time 

interval.

Population Viability Analyses (PVA) of Count 

Data

Midway Atoll.—The temporal trend in Robs was not 

significantly different from zero (slope = 0.0024, t = 0.386, 

p = 0.709), with most values within 0–0.05 (fig. 15). 

However, there was high inter-annual variation in the number 

of breeding pairs attending the atoll, which is reflected in 

the Robs values. The relation between Robs and colony 

size with time (t-1) is negative but not significant 

(slope = -2.9 × 10-5, t = -1.647, p = 0.134). The LRT indicates 

no significant improvement in using the logistic over the 

exponential model for explaining the Robs data (LR = 0.91, 

p = 0.617).

The exponential model indicates a positive growth 

rate of â = 0.015 (95 percent [CI]: 0.011 – 0.019), with the 

environmental stochasticity having a strong influence on Robs

(table 13). After sampling error was included, the logistic 

model presented a poorer fit (higher AICc value) than the 

exponential model. In both cases, there are positive and 

negative deviations from the general trend in 1996 and 1999, 

respectively. A positive trend in the residuals also is observed 

in 2003–04.

Population projections based on the exponential model 

suggest in 60 years the population has a 50 percent chance 

of increasing 1.36 times (CI: 1.23– 1.49). The probability of 

decreasing 49 percent (CI: -53 – -45 percent) in this period is 

0.10, and there is only a 0.225 probability of decreasing at all 

(fig. 16).
40 Status Assessment of Laysan and Black-Footed Albatrosses, North Pacific Ocean, 1923–2005

tac_08_9354_0255_Albatrosses_Fig16

-1.0 -0.5 0.0 0.5 1.0 1.5 2.0

0

0.1

0.2

0.3

0.4

0.6

0.5

RATE OF CHANGE

CUMULATIVE PROBABILITY

0

50,000

100,000

150,000

TIME (YEARS)

NUMBER OF BREEDING PAIRS

2010 2020 2030 2040 2050 2060

A.

B.

tac_08_9354_0255_Albatrosses_Fig15

17,000 18,000 19,000 20,000 21,000 22,000

NUMBER OF BREEDING PAIRS

1991 1993 1995 1997 1999 2001 2003 2005

OBSERVED GROWTH RATE DISTRIBUTION

OBSERVED GROWTH RATE DISTRIBUTION (ROBS) FREQUENCY

−0.2 −1.0 0.0 0.1 0.2

-0.25

-0.2

-0.15

-0.1

-0.05

0

0.05

0.1

0.15

0.2

-0.2

-0.15

-0.1

-0.05

0

0.05

0.1

0.15

0

1

2

3

4

5

6

A. Frequency distribution of Robs. 

Sand

Eastern

Midway

Trendline y = 0.0024x - 4.6915

y = -3E-05x + 0.5828

R 2 = 0.2317

R 2 = 0.0163

B. Inter-annual variability of Robs. 

C. Relation between Robs and the breeding population size (time: t-1). 

Figure 15. Observed growth rate distribution (Robs) for the 

black-footed albatross breeding population, Midway Atoll.

Figure 16. Population projection (A, n = 30) and 

cumulative probability (B) that a given rate of population 

change is reached over 60 years using the exponential 

model for black-footed albatross, Midway Atoll.
Population Status and Trends 41

Laysan Island.—Colony size estimates were derived 

from transects (1992–2005) and direct counts (1998–2005). 

Direct counts of colony size have considerably lower variance 

than transect estimates (see methods, appendix C). However, 

the available time-series data for direct counts is shorter, 

thus it may only indicate transient trends in the breeding 

population (fig. 17). Estimates from a re-analysis of transect 

samples using a negative binomial distribution represent a 

better estimate of the colony size, as samples were highly 

skewed (see methods, appendix C). Graphical examination 

also indicates that the re-estimations of the population size 

are closer to the direct counts than the original transect 

estimations, which failed to represent the relation between 

Robs and population size (fig. 17). The new estimates appear 

to under-estimate population size in most years, but this 

pattern is consistent throughout the series. Accordingly, only 

re-estimations from transect samples and direct counts were 

used to estimate population trends.

The colony growth rate derived from transects samples 

was positive, but not significantly different from zero 

(exponential model: â = 0.007, 95 percent CI [CI]: -0.045– 

0.061) (table 14; fig. 18). Population projections using this 

estimate indicate a median rate of population increase over the 

next 60 years of 54.7 percent (CI: 34.1 – 80.1). This appears 

to be overly optimistic given the 0.425 probability that the 

population would decrease by 12.3 percent (CI: -23.8 – 0.6) 

and the 0.35 probability that it would decrease by greater than 

50 percent (median: -51.3 percent, CI: -57.5 – -44.0; fig. 19). 

In addition, analysis using direct counts suggests a negative 

population growth rate, â = -0.013 (CI: -0.017 – -0.009; 

exponential model; table 15).

NUMBER OF BREEDING PAIRS

0

10,000

20,000

30,000

40,000

50,000

60,000

1990 1992 1994 1996 1998 2000 2002 2004 2006

Transects, corrected

Transects, FWS 95-percent confidence limits

Direct counts

Figure 17. Population estimates for black-footed albatross, Laysan Island.

French Frigate Shoals.—The trend in Robs for the entire 

atoll is not statistically different from zero (slope = 0.0007, 

t = 0.121, p = 0.905), whereas the relation of Robs to colony 

size is significant and negative (slope = -0.0002, t = -3.499, 

p = 0.002; fig. 20), characteristic of populations with strong 

first-order negative feedback on population size, and close to 

their carrying capacity (Royama, 1992; Berryman and others, 

2002). The LR test, using the T12

2

 version (Dennis and Taper, 

1994), also indicates that the logistic model fits the data better 

than the exponential model (T12

2

 = 10.41, p = 0.031).

As with both islands described earlier, Robs values 

are strongly affected by environmental stochasticity, as 

â < σenv  (exponential model; table 16). Analysis of residuals 

indicates that in 1984–85, there was a negative deviation 

from the general trend, followed by a corresponding positive 

deviation in Robs values. These deviations appear to be the 

result of changes in the number of breeding pairs on WhaleSkate, as neither Tern nor East Islands showed significant 

changes in their colony sizes during 1984–87 (fig. 14). The 

logistic model indicates another unusual deviation from the 

deterministic model in 1995, which again is related to changes 

in the breeding population on Whale-Skate (fig. 14). In 1997, 

Whale-Skate disappeared due to erosion.

The growth rate estimated with the exponential 

model indicates an increase in colony size, with â = 0.010 

(95-percent CI [CI]: 0.008 – 0.012) (table 16). Accordingly, 

population projections based on the exponential model 

suggest that in 60 years the population will increase by 74.2 

percent (CI: 49.9 – 100.6; p = 0.50), although there is a 0.40 

probability that the population would decrease greater than 

10.9 percent (CI: -23.4 – 2.9) and a 0.325 probability that 

this decrease would be greater than 47 percent (CI: -55 – -39; 

fig. 21). 
42 Status Assessment of Laysan and Black-Footed Albatrosses, North Pacific Ocean, 1923–2005

Data: 

1992–2005 

[N(Robs)=11] 

Parameters fitted 

(mean ± 1 SE) logL(φ) AICc

Including sampling error + environmental stochasticity

Exponential 

model ˆ = 0.01501 (0.01148; 0.01853)

= 0.06879 (0.06022; 0.07816)

= 0.06720

= 0.01469

tot

env

s error

a

−







σ

σ

σ

14.359 -23.219

Logistic 

model -5 -5 -5

ˆ = 0.59316 (0.47154; 0.72880)

ˆ = 2.9649×10 (2.3368×10 ;3.6561×10 )

ˆ = 20,006

0.06618 (0.05904; 0.07315)

= 0.06453

= 0.01469

tot

env

s error

a

b

K

σ

σ

σ −

−

 =





13.967 -18.505

Table 13. Parameter estimation for exponential and logistic R-function models fitted to 

black-footed albatross Robs data, Midway Atoll.

[Black-footed albatross Robs data from U.S. Fish and Wildlife Service, unpub.data, 1980–2005; Flint, 

2005. Robs, observed growth rate distribution; SE, standard error. aˆ, population growth rate; σtot  , total 

variation; σenv  , environmental stochasticity; σs error −  , sampling error; – ˆ

b , density-dependent parameter; 

K, carrying capacity]

Data: 

1992–2005 

[N(Robs)=13] 

Parameters fitted 

[mean and (95-percent confidence limit)] logL(φ) AICc

Including sampling error + environmental stochasticity

Exponential 

model ˆ = 0.00746 (-0.04549; 0.06144)

= 0.28828 (0.16834; 0.43672)

= 0.16155

= 0.23876

tot

env

s error

a

−







σ

σ

σ

-1.402 8.304

Logistic 

model -5 -5 -5

1

ˆ = 1.01612 (0.56609; 1.54077)

ˆ = 4.8934×10 (2.7274×10 ; 7.6219×10 )

ˆ = 20,765

0.20709 (0.12383; 0.31868)

= 0

= 0.23876

tot

env

s error

a

b

K

σ

σ

σ −

−

 =





2.816 3.797

1

Estimation was negative.

Table 14. Parameter estimation for exponential and logistic R-function models fitted to 

black-footed albatross Robs data after re-analysis of transect samples, Laysan Island.

[Black-footed albatross Robs data from U.S. Fish and Wildlife Service, unpub.data, 1980–2005; Flint, 

2005. Robs, observed growth rate distribution; aˆ, population growth rate; σtot  , total variation; σenv  , 

environmental stochasticity; σs error −  , sampling error; – ˆ

b , density-dependent parameter; K, carrying 

capacity]
Population Status and Trends 43

Data: 

1998–2005 

[N(Robs)=7] 

Parameters fitted

[mean and (95-percent confidence limit)] logL(φ) AICc

Including sampling error + environmental stochasticity

Exponential 

model ˆ = -0.01278 (-0.01669; -0.00872)

= 0.09083 (0.07766; 0.10390)

= 0.08882

= 0.01900

tot

env

s error

a

−







σ

σ

σ

7.398 -7.796

Logistic 

model -5 -5 -5

ˆ = 0.80856 (0.68629; 0.92837)

ˆ = 3.8693×10 (3.2973×10 ; 4.4298×10 )

0.07200 (0.06277; 0.08100)

= 0.06945

= 0. 01900

tot

env

s error

a

b

−

−

 =





σ

σ

σ

9.662 -5.324

Table 15. Parameter estimation for exponential and logistic R-function models fitted to 

black-footed albatross Robs data derived from direct nest counts, Laysan Island.

[Black-footed albatross Robs data from U.S. Fish and Wildlife Service, unpub.data, 1980–2005; Flint, 

2005. Robs, observed growth rate distribution; aˆ, population growth rate; σtot  , total variation; σenv  , 

environmental stochasticity; σs error −  , sampling error; – ˆ

b , density-dependent parameter]

Data: 

1982–2005 

[N(Robs)=23] 

Parameters fitted 

[mean and (95-percent confidence interval)] logL(φ) AICc

Including sampling error + environmental stochasticity

Exponential 

model ˆ = 0.01044 (0.00834; 0.01241)

= 0.18967 (0.18307; 0.19617)

= 0.18912

= 0.01441

tot

env

s error

a

−







σ

σ

σ

6.109 -7.618

Logistic 

model -4 -4 -4

ˆ = 0.76052 (0.72957; 0.79302)

ˆ = 1.9421×10 (1.8613×10 ; 2.0251×10 )

ˆ = 3,916

0.15617 (0.15141; 0.16069)

= 0.15550

= 0.01441

tot

env

s error

a

b

K

σ

σ

σ −

−

 =





11.118 -14.973

Table 16. Parameter estimation for exponential and logistic R-function models fitted to 

black-footed albatross Robs data, French Frigate Shoals.

[Black-footed albatross Robs data from U.S. Fish and Wildlife Service, unpub.data, 1980–2005; Flint, 

2005 Robs, observed growth rate distribution; aˆ, population growth rate; σtot  , total variation; σenv  , 

environmental stochasticity; σs error −  , sampling error; – ˆ

b , density-dependent parameter; K, carrying 

capacity]
44 Status Assessment of Laysan and Black-Footed Albatrosses, North Pacific Ocean, 1923–2005

tac_08_9354_0255_Albatrosses_Fig18

OBSERVED GROWTH RATE DISTRIBUTION

FREQUENCY

0

1

2

3

4

NUMBER OF BREEDING PAIRS

-0.60

-0.40

-0.20

0.00

0.20

0.40

0.60

-0.60

-0.40

-0.20

0.00

0.20

0.40

0.60

15,000 20,000 25,000 30,000 35,000 40,000

−0.3 −0.2 −0.1 0.0 0.1 0.2 0.3

1991 1993 1995 1997 1999 2001 2003 2005

A. Frequency distribution of Robs after re-analysis of transect samples. 

B. Inter-annual variability of Robs. 

C. Relation between Robs and the breeding population size (time: t-1). 

OBSERVED GROWTH RATE DISTRIBUTION (ROBS)

Transects, corrected

Direct counts

Transects, FWS

tac_08_9354_0255_Albatrosses_Fig19

-1.0 -0.5 0.0 0.5 1.0

0

0.1

0.2

0.3

0.4

0.6

0.5

RATE OF CHANGE

CUMULATIVE PROBABILITY

0

50,000

100,000

150,000

200,000

TIME (YEARS)

NUMBER OF BREEDING PAIRS

2010 2020 2030 2040 2050 2060

A.

B.

Figure 18. Observed growth rate distribution (Robs) for the 

black-footed albatross breeding population, Laysan Island.

Figure 19. Population projection (A, n = 30) and 

cumulative probability (B) that a given rate of population 

change is reached over 60 years using the exponential 

model and re-analyzed transect data for black-footed 

albatross, Laysan Island.
Population Status and Trends 45

tac_08_9354_0255_Albatrosses_Fig20

y = 0.0007x – 1.3142

y = -0.0115x + 23.055

y = -0.0002x + 0.7611

y = -0.0002x + 0.2479

R2 = 0.0007

R 2 = 0.3943

R2 = 0.3577

R2 = 0.4242

OBSERVED GROWTH RATE DISTRIBUTION

FREQUENCY

NUMBER OF BREEDING PAIRS

-0.4

-0.3

-0.2

-0.1

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

1975 1980 1985 1990 1995 2000 2005

-0.4

-0.3

-0.2

-0.1

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0 1,000 2,000 3,000 4,000 5,000 6,000

−0.4 −0.2 0.0 0.2 0.4 0.6

4

3

2

1

0

A. Frequency distribution of Robs for the entire atoll. 

B. Inter-annual variability of Robs. 

C. Relation between Robs and the breeding population size (time: t-1). 

OBSERVED GROWTH RATE DISTRIBUTION (ROBS)

FFS trendline

Tern

FFS

Tern trendline

tac_08_9354_0255_Albatrosses_Fig21

-1.0 -0.5 0.0 0.5 1.0 1.5 2.0

0

0.1

0.2

0.3

0.4

0.6

0.5

RATE OF CHANGE

CUMULATIVE PROBABILITY

0

50,000

100,000

150,000

TIME (YEARS)

NUMBER OF BREEDING PAIRS

2010 2020 2030 2040 2050 2060

A.

B.

Figure 20. Observed growth rated distribution (Robs) for the 

black-footed albatross breeding population on all of French 

Frigate Shoals (Robs-FFS) and Tern Island (Robs-Tern) only.

Figure 21. Population projection (A, n = 30) and 

cumulative probability (B) that a given rate of population 

change is reached over 60 years using the exponential 

model for black-footed albatross, French Frigate Shoals.
46 Status Assessment of Laysan and Black-Footed Albatrosses, North Pacific Ocean, 1923–2005

Matrix Model Analyses

Trend over the Past Century.—The size of the blackfooted albatross population prior to feather hunting is 

unknown, but it is believed that harvesting greatly reduced 

the population, and several colonies were known to have been 

extirpated (Rice and Kenyon, 1962a; Spennemann, 1998). 

Following this era, the black-footed albatross population 

increased from ca. 18,000 breeding pairs in 1923 to ca. 

61,000 breeding pairs in 2005 (fig. 22). Population growth 

has occurred despite major human disturbance of breeding 

colonies, primarily at Midway Atoll and French Frigate Shoals 

(fig. 13), and intense fishing mortality. The joint effect of 

these two factors led to a significant reduction of the observed 

population growth rate relative to the growth rate prior to the 

1940s. The median population growth rate for 1955–2003 

was 1.003 compared to the natural growth rate estimate of 

λ = 1.035 (log2A model; table 18), implying a 3.2 percent 

decrease in population growth due to fishery mortality.

In reconstructing the historic population trend for blackfooted albatrosses, we did not find support for the population 

estimate of Fisher and Baldwin (1946), but we did for the 

estimates of Rice and Kenyon (1962a). Our findings are 

based on the assumption that the data on control programs 

presented in table 2 are accurate. Observations by Fisher and 

Baldwin (1946) suggest that the total number of black-footed 

albatrosses killed or prevented from nesting, as presented in 

table 2, may be greatly underestimated.

Parameter Estimation.—The model we used for 

estimating demographic parameters and the population 

growth rate was a density-independent, age-structured, matrix 

model similar to that used by Cousins and Cooper (2000) and 

Lewison and Crowder (2003), thus differences in our results 

are not due to model structure. In all scenarios, the current 

breeding population size was below the maximum nesting 

capacity estimated by K1 (68,000 pairs; fig. 22). Demographic 

estimates presented are within the range of reported values 

for each parameter (table 13) and represent values necessary 

to maintain the measured population growth rate given 

the documented Navy activities during 1950 to 2005 and 

the estimated fisheries bycatch. Thus, these values are not 

maximum values for the species, and calculated population 

growth rates (λ = 1.031-1.036) are below previous estimates 

for the species (λ = 1.04, Cousins and Cooper, 2000; λ = 

1.059, Niel and Lebreton, 2005). This suggests the influence 

of additional factors affecting the population growth rate, such 

as fishery bycatch, density-dependence, interisland variation 

in breeding success, recruitment compensation, or space 

limitation.

 The 2005 fishery bycatch (fig. 23) is within the mortality 

level that can be sustained by the black-footed albatross 

population without causing a decrease. However, this 

should be interpreted with caution given the uncertainty of 

bycatch estimates (as indicated by the overlap of the bycatch 

confidence interval with the sustainable mortality level for 

black-footed albatrosses). Our analyses support the lower 

bycatch hypothesis for the International pelagic longline 

fishery, as estimated for the Hawaiian-based fleet during 

1997–2000 (see appendix A for details of bycatch hypotheses). 

Finally, the assumption of zero bycatch prior to 1970, as 

assumed by previous analyses (Cousins and Cooper, 2000; 

Lewison and Crowder, 2003), is not supported by our model.

Fishery Impact.— All model scenarios indicate that the 

overall bycatch level for the period when pelagic longline and 

high seas driftnet fisheries were both active, was greater than 

the potential growth capacity for the species. Consequently, 

the closure of the high seas pelagic driftnet fishery was 

critical to preventing further population decline. Nevertheless, 

estimated bycatch from the longline fleet was greater than for 

the driftnet fleet estimates (fig. 4), and remains as of 2005 

as the most important source of mortality for black-footed 

albatrosses.

 During the 1980s, co-occurrence of driftnet and pelagic 

longline fisheries caused a reduction in adult survival, as 

indicated by our results and those from capture-recapture data 

(table 18). Weighted averages of estimates by Kendall (U.S. 

Geological Survey Patuxent Wildlife Research Center, written 

commun., 2005) provided a better fit to survival estimates than 

our model, indicating that island-specific factors affect these 

parameters. This is further supported by the lack of fit of our 

model to the breeding population trend during the 1950s and 

1960s, indicating that albatross numbers killed by humans 

during this period may have been significantly underestimated.

0

20,000

40,000

60,000

80,000

100,000

1920 1930 1940 1950 1960 1970 1980 1990 2000 2010

BREEDING POPULATION SIZE

H2-mean

K1

H1-mean

K2

World

Figure 22. World black-footed albatross breeding 

population trend, as derived from estimations at each 

island. 
Population Status and Trends 47

Our estimate of the maximum PBR for black-footed 

albatrosses is 11,980 birds per year (range: 10,579–12,796). 

This result is comparable, although somewhat higher, than 

previous estimates of 8,850 (Niel and Lebreton, 2005) and 

10,000 birds per year (Cousins and Cooper, 2000). Our 

estimate of the 2005 bycatch level (fig. 23) is lower than these 

PBRs, but Lewison and Crowder’s (2003) moderate bycatch 

scenario is higher than some PBRs, and their worst bycatch 

scenario is higher than all PBRs. So if these bycatch levels 

are attained, then our model predicts the population would 

decline.

The maximum PBR level is calculated using estimates 

of the population growth rate and size. Wade (1998) proposed 

using density-dependent (0.5) and recovery (0.5) factors for 

estimating PBR, and we have followed that recommendation. 

A recovery factor (Fr) is used to compensate for 

uncertainty in parameter estimates, as for example, fishery 

bycatch, which is difficult to estimate (Wade, 1998). Here we 

used a Fr of 0.5, a value typically used when estimating PBRs. 

Use of a recovery factor is an important safeguard, especially 

because we have no direct estimates of the current bycatch for 

the International pelagic longline fishery, the largest threat to 

albatross species worldwide.

Table 17. Demographic parameter estimates [mean ± 1 SD (range)] available for the black–footed 

albatross. 

[Overall estimates of the survival rates were calculated using W.L. Kendall estimates (U.S. Geological Survey, 

Patuxent Wildlife Research Center, written commun., 2005) and the proportion of birds breeding at Midway Atoll and 

elsewhere, as derived from the historical breeding population reconstruction]

Parameter Kure Atoll Midway Atoll Tern Island Overall

Breeding 

frequency

1

1961–62

0.70

2

1998–1999

0.75±0.02

0.83±0.02

Breeding 

success

3

1963–68

0.42 ± 0.04

(0.36–0.46)

4

1992–2001

0.55 ± 0.16

(0.34–0.79)

4

1980–2003

0.69 ± 0.10

(0.38–0.78)

Juvenile 

survival 

rate

3

1963–68

0.750 ± 0.057

(0.689–0.822)

5

1957

0.771, 0–5 yr

2

1990–1991

0.793, 0–5 yr 

(0.760–0.824)

6

1963–82

0.40 ± 0.04

6

1963–1982

0.76 ± 0.08

6

1963–82

0.688

6

1983–93

0.92 ± 0.03

6

1983–1993

0.56 ± 0.05

6

1983–93

0.668

6

1994–2002

0.97 ± 0.004

6

1994–2002

0.97 ± 0.01

6

1994–2002

0.993

Adult 

survival 

rate

5

1961–67

0.923 (0.810–0.994)

2

1990s

0.890 (0.870–0.910)

6

1963–82

0.87 ± 0.01

6

1963–1982

0.94 ± 0.02

6

1963–82

0.926

6

1983–93

0.99 ± 0.001

6

1983–1993

0.85 ± 0.03

6

1983–93

0.892

6

1994–2002

0.92 ± 0.07

6

1994–2002

0.99 ± 0.002

6

1994–2002

0.967

1

Robbins (1966).

2

Viggiano (2001).

3

Woodward (1972). 

4

U.S. Fish and Wildlife Service, unpub. data, 1980–2005. 

5

Cousins and Cooper (2000).

6

W.L. Kendall (U.S. Geological Survey, Patuxent Wildlife Research Center, written commun., 2005).
48 Status Assessment of Laysan and Black-Footed Albatrosses, North Pacific Ocean, 1923–2005

Figure 23. Potential Biological Removal estimate using R/4, R/2, and R, and initial population sizes of black-footed albatross as 

obtained from each estimated trend for 2004. 

Table 18. Parameter estimates [median (95-percent CI)] for the black–footed albatross population–projection matrix.

[Descriptions of parameters and models are shown in appendix C. b, constant measuring the strength of density-dependence. Lambda (λ) max, maximum 

growth rate of the population. NA, not applicable]

Parameters

Model: Exp-A Model: Log-2A Model: Log-2G Model: Log-2H

Exponential; 

Low bycatch 

(mean for H1)

Logistic; 

Low bycatch 

(mean for H1)

Logistic; 

Low bycatch 

(2.5 percentile for H1)

Logistic; 

Low bycatch 

(mean × 1.14 for H1)

Breeding frequency 0.67

(0.65–0.74)

0.67

(0.65–0.72)

0.71

(0.65–0.80)

0.67

(0.65–0.68)

Breeding success 0.63

(0.51–0.71)

0.61

(0.51–0.70)

0.57

(0.50–0.67)

0.66

(0.63–0.71)

Survival fledglings 0.810

(0.710–0.890)

0.820

(0.720–0.890)

0.78

(0.70–0.89)

0.835

(0.755–0.877)

Survival juveniles 0.940

(0.920–0.985)

0.950

(0.930–0.980)

0.94

(0.93–0.97)

0.940

(0.930–0.950)

Survival adults 0.945

(0.940–0.965)

0.945

(0.940–0.960)

0.95

(0.94–0.96)

0.945

(0.941–0.950)

b NA 5.14×10-10

(4.43×10-11 – 9.63×10-10)

4.63×10-10

(1.39×10–11 – 9.58×10-10)

2.82×10–10

(2.33×10-11 – 9.31×10-10)

Lambda (λ) max 1.035

(1.034–1.036)

1.035

(1.034–1.036)

1.032

(1.031–1.033)

1.036

(1.036–1.036)

N 100 100 100 1

12

1

Iteration process stopped after 21 hours.

tac_08_9354_0255_Albatrosses_Fig23

1950 1960 1970 1980 1990 2000 2010

0

5,000

10,000

15,000

20,000

NUMBER OF ADULTS AND JUVENILES

Log2A

EXPLANATION

Log2G

Log2H

Navy removals

Potential biological removal estimate using R/4

Log2A

Log2G

Log2H

Potential biological removal estimate using R/2

Log2A

Log2G

Log2H

Potential biological removal estimate using R

H1-mean

H1-low

H1-mean*1.14

Fishery bycatch levels
Population Status and Trends 49

Discussion: Laysan and Black-Footed 

Albatrosses Population Analyses

Population Viability Analyses

PVA results indicate that colonies at Midway Atoll 

(black-footed albatrosses only) and French Frigate Shoals 

(Laysan and black-footed albatrosses) will have a positive 

growth rate over the next 60 years and they have a 0.5 

probability of increasing 0.74–8.36 times their present 

population sizes. At Laysan Island, PVA results for Laysan and 

black-footed albatrosses are less optimistic. After re-analyzing 

the transect data, projections for both albatross species suggest 

a positive population change over the next 60 years (BFAL: 

median = 0.55; LAAL: median = 0.16), but there is a high 

probability that their populations will decrease greater than 

50 percent in 60 years (figs. 8 and 19). An analysis of direct 

counts for black-footed albatrosses indicates a negative trend 

over time (â = -0.013, table 15).

Population projections are determined by population 

growth rate â and the environmental stochasticity, σenv  , with 

sampling variance removed. Growth rate determines the 

general trend in the population over time, with negative values 

indicating a decline. However, environmental stochasticity 

plays an important role in determining PVA results, as this 

parameter significantly affects the effective population 

growth in a given year, with higher σenv  values producing more 

pessimistic PVA results (Morris and Doak, 2002).

 For all islands and species analyzed, â << σenv  (fig. 24), 

and consequently, environmental stochasticity has a profound 

effect on the PVA results. For example, even when the 

â values estimated for the black-footed albatross colonies 

at Midway Atoll and French Frigate Shoals are similar, the 

higher environmental variance in the French Frigate Shoals 

population (fig. 24) implies larger probabilities of decreasing 

greater than 50 percent (figs. 16 and 21).

Another important factor affecting results is the accuracy 

of the parameter estimates. The analyses with parameter 

estimates developed from conducting direct nest counts are 

more accurate than analyses based on transect sampling 

(fig. 24). PVA analyses conducted for black-footed albatross 

on Laysan Island, where population estimates are derived from 

transect sampling, indicated a population increase but also 

had the highest probabilities of population decreases over the 

next 60 years. Parameter estimation based on direct counts of 

all black-footed albatross nests present a negative trend with 

narrower confidence intervals, but the short time series of data 

may produce misleading conclusions. However, application 

of this negative growth rate, derived from direct counts, to 

the best historical estimates (Rice and Kenyon, 1962a) during 

the 1956 and 1957 breeding seasons accurately projects the 

current breeding population. 

0

0.1

0.2

0.3

0.4

0.5

0.6

-0.05 -0.04 -0.03 -0.02 -0.01 0.00 0.01 0.02 0.03 0.04 0.05 0.06 0.07

BF-Laysan1

BF-Laysan2

BF-Midway

BF-FFS

LA-Laysan1

LA-Laysan2

LA-FFS

â

σ-ENV

Figure 24. Species and islands comparison of the population growth rate, â, and the environmental variance, σenv  , estimated 

with the exponential model (mean and 95-percent CI). 
50 Status Assessment of Laysan and Black-Footed Albatrosses, North Pacific Ocean, 1923–2005

 For most bird species, census variability reflects true 

changes in the total number of individuals (that is, Laysan 

finch; see Dennis and others, 1991), but for breeding 

albatrosses, censuses of nesting birds also are affected by 

the fraction of mature birds attempting to nest that year. 

Accordingly, σenv  should be primarily interpreted as an 

environmental variable that affects the attendance pattern 

of breeding birds in the colony. This does not preclude use 

of breeding pair censuses to estimate albatross population 

trends, because substantial decreases in population size have 

been detected using these types of data (that is, Wandering 

albatrosses, Weimerskirch and others, 1997a; Wandering, 

Grey-headed, and Black-browed albatrosses, Croxall and 

others, 1998), but longer time-series data are needed. In this 

context, only time-series data from French Frigate Shoals are 

long enough to show a potential change over time. Analysis 

from this atoll indicates that both albatross species have 

positive population growth rates, and their median trend is 

for growth over the next 60 years. However, this conclusion 

should be viewed with caution since French Frigate Shoals 

was occupied by the military until 1979, the atoll population 

represents only a small fraction of the species population, and 

important local factors may differ among islands.

The PVA analyses for black-footed albatrosses indicate 

that under conditions present in 2005, the overall population 

is not at risk of a substantial decrease over the next 60 

years, but for Laysan Island, there is great uncertainty in the 

parameter estimates. Colony size at Laysan Island should 

be carefully monitored and abundance estimates improved. 

Results from French Frigate Shoals, for which the longest time 

series data exists, indicate that the number of breeding pairs 

of both albatross species increased, even during the period 

of high fishing mortality in the 1980s. If fishing mortality is 

homogeneously distributed among all NWHI colonies, this 

suggests that another factor in addition to fishing mortality, 

perhaps nest site availability, may be reducing the observed 

population growth rates at other islands. The closure of the 

military station at French Frigate Shoals in 1980 also may 

explain the population growth at this site, as birds displaced 

by military activities returned to breed. Colonies at French 

Frigate Shoals and Midway Atoll grew faster after ‘control’ 

programs were stopped (see section, “Conflicts with Military 

Activities;” Gould and Hobbs, 1993), perhaps indicating that 

space was a limiting factor or that breeders were precluded 

from nesting. By contrast, the breeding population size of 

Laysan albatrosses appears stable on Laysan Island, although 

the black-footed albatross population has decreased (figs. 5

and 13; Gould and Hobbs, 1993).

Incidental Mortality of Albatrosses

Incidental mortality during fishing operations is believed 

to be a major threat to the long-term viability of black-footed 

albatrosses (Cousins and Cooper, 2000; Lewison and Crowder, 

2003; Niel and Lebreton, 2005). The projected population 

decrease due to this cause motivated the IUCN to list blackfooted albatrosses as Endangered in 2003 (International Union 

for the Conservation of Nature and Natural Resources, 2004). 

The population growth rate (λ) potential and fishery bycatch 

levels used in these analyses differed from ours because they 

used different estimates of adult and juvenile survival rates, 

both of which have a large impact on λ (Cousins and Cooper, 

2000), and fishery bycatch estimates.

Maximum Potential Biological Removal (PBR) for blackfooted albatrosses has been estimated to be 8,850 to 10,000 

birds/year (Niel and Lebreton, 2005; Cousins and Cooper, 

2000, respectively). The 95-percent confidence interval for 

black-footed albatross bycatch falls within this range (fig. 23), 

and therefore requires careful examination, especially because 

the PBR estimate does not consider other sources of mortality.

 The analysis of Lewison and Crowder (2003) assumed 

an initial condition in which λ~1 (stability), and added 

estimates of fishery bycatch for the International pelagic 

longline fleet in the North Pacific Ocean. Predictions from this 

modeling indicated that the black-footed albatross population 

was likely to decline rapidly over the next 60 years. This 

steep decline appears to be the result of assuming that there 

was no fishery bycatch during the 1960s to 1970s, the time 

period over which demographic parameters were estimated. 

Fishery effort data from the Ocean Fisheries Program indicates 

that bycatch probably was significant during this era (fig. 4). 

Thus, when bycatch was added to the model, the influence of 

fisheries was approximately doubled, leading to a prediction 

of rapid population decreases.

We analyzed the fishery bycatch data from the North 

Pacific Ocean since 1950 and found that the International 

pelagic longline fleet maintained a similar fishing effort 

from the 1960s to the present, with perhaps a slight decrease 

in effort during recent years (fig. 4). Because we have no 

evidence to suggest that the bycatch rate for this fishery 

changed over this period, an era with no mitigation measures 

in place, we feel that past analyses likely doubled the bycatch 

rate.
Acknowledgments 51

Conclusions

The Laysan albatross breeding population increased 

from an estimated 18,000 pairs in 1923 to 590,000 pairs in 

2005, and currently does not appear to be at risk of decline 

due to fishery bycatch. The large increase in population size 

during the past 83 years, is likely a response to cessation 

of persecution by feather hunters and the military, and an 

increase in nesting area at some colonies. Analysis of linear 

trends in the population showed a positive change over 

1923–2005 and 1957–2005, and a stable size during 1992–

2005. PVA results for French Frigate Shoals indicate that the 

population is currently stable and has a 50-percent probability 

of increasing 8.36 times in the next 60 years, but it also has a 

28-percent probability of decreasing 0.24 times. For Laysan 

Island, the PVA predicts that the median population size will 

increase by 15.7 percent in the next 60 years, but there is a 

45-percent probability that the population will decrease by 

greater than 50 percent. PVA analysis was not conducted for 

Midway Atoll due to the paucity of data. Matrix modeling 

results indicate that the Laysan albatross population, summed 

across all three colonies, is increasing at 6.7 percent a year, 

and that the estimated bycatch of 2500 birds/year is below the 

PBR.

The black-footed albatross breeding population increased 

from an estimated 18,000 pairs in 1923 to 61,000 pairs in 

2005, and currently may be at risk of decline due to fishery 

bycatch. As with Laysan albatross, the increase in population 

size over the past 83 years probably is in response to the 

end of persecution at the nesting colonies. Analysis of linear 

trends in the population showed a positive change over 1923 

to 2005, no change from 1957 to 2005, and no change from 

1998 to 2005. PVA results for French Frigate Shoals indicate 

that the population is increasing at 1 percent a year and has a 

50-percent probability of increasing by 74 percent in the next 

60 years, but it also has a 35-percent probability of decreasing 

by greater than 47 percent. For Laysan Island, the population 

is stable, and the PVA predicts the median population growth 

rate will increase by 54.7 percent. However, this should be 

taken with caution because there is a 35-percent probability 

that the population would decrease by greater than 50 percent. 

For Midway Atoll, the population is increasing annually by 

1.5 percent, and the PVA predicts a 50-percent probability of 

a 1.36 times increase in the population size and a 22.5-percent 

probability of the population decreasing by any amount. 

Matrix modeling results indicate that the black-footed 

albatross population, summed across all three colonies, is 

stable, or slightly increasing, with a population growth rate of 

0.3 percent per year. The 2005 estimate of bycatch is 5,228 

birds per year, but if this value is doubled, a safeguard for 

underestimating bycatch, it approaches the PBR of 11,980 

birds per year, although the upper 95-percent confidence limit 

(17,486) exceeds the PBR. 

Our knowledge of interactions of Laysan and blackfooted albatrosses with fishing operations is imperfect, partly 

because of the difficulty of obtaining reliable bycatch data. 

Results from the matrix modeling indicate that fishery bycatch 

is not significantly affecting the size of the Laysan albatross 

population, but may be causing a decrease in black-footed 

albatross populations. 

Acknowledgments

Special thanks to S. Fitzgerald, K. Rivera, J. Bisson, 

B. Miyamoto, C. Tokita, J. D. Kelly (NOAA Fisheries) and 

G. Williams (International Pacific Halibut Commission) 

for providing data and insights on the U.S. fisheries and 

observer programs. J. Smith (University of Washington) and 

K. Morgan (Environment Canada) provided valuable insights 

from the Canadian observer program. Thanks to E. Flint, B. 

Zaun, L. Young, J. Klavitter (U.S. Fish and Wildlife Service), 

and M. Rauzon (Marine Endeavors) for providing data on 

the U.S. colonies; R.W. Henry (University of California at 

Santa Cruz), B. Keitt (Island Conservation, University of 

California at Santa Cruz), and R. Wanless (BirdLife Global 

Seabird Programme) for data on the Mexican colonies; 

and, T. Deguchi and N. Nakamura (Yamashina Institute for 

Ornithology) and H. Hasegawa (Toho University, Japan,) for 

the Japanese colonies. Thanks to R. Young (U.S. Fish and 

Wildlife Service) for producing the breeding distribution map 

(fig. 1), C. Small and F. Taylor (BirdLife International, Global 

Seabird Programme) for producing the at-sea distribution 

maps (fig. 2), M. Morin for analyses of reproductive success, 

S. Thomsen for summarizing the contaminant literature.

We thank the following for providing reviews of an 

earlier draft: J. Bisson, L. Blight, B. Bortner, J. Croxall, 

T. Deguchi, K. Dietrich, M. Finkelstein, S. Fitzgerald, 

H. Freifeld, T. Good, D. Goodman, C. Harrison, R. Henry, 

S. Hoyle, D. Hyrenbach, A. Katekaru, B. Keitt, W. L. 

Kendall, J. Klavitter, K. Kuletz, J.D. Lebreton, R. Lewison, 

J. Ludwig, E. Melvin, K. Morgan, K. Rivera, F. RiveraMilán, C.S. Robbins, M. Romano, S. Shaffer, J. Smith, J.L. 

Trapp, U. Varanasi, S. Veran, G. Williams, B. Zaun. A special 

thanks to T. Zimmerman (U.S. Fish and Wildlife Service) 

for continued support throughout this project. We also would 

like to acknowledge the editing assistance of J. Erickson and 

R. Jacobs (USGS, Forest and Rangeland Ecosystem Science 

Center). 

Funding for this assessment was provided by the U.S. 

Fish and Wildlife Service, Division of Migratory Birds and 

Habitat Programs, Pacific Region.
52 Status Assessment of Laysan and Black-Footed Albatrosses, North Pacific Ocean, 1923–2005

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60 Status Assessment of Laysan and Black-Footed Albatrosses, North Pacific Ocean, 1923–2005

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Appendix A 61

Appendix A: Bycatch Estimation

Driftnet Fisheries

Three types of large-scale pelagic driftnet fisheries 

operated in the North Pacific: salmon driftnet fishery by 

Japan; squid driftnet fishery by Japan, Republic of Korea and 

Taiwan; and large-mesh driftnet fishery by Japan and Taiwan 

(Ogi and others, 1993). United Nations General Assembly 

Resolution 46-215 (adopted December 1991), called for a 

global moratorium on all large-scale pelagic driftnet fishing by 

December 31, 1992.

No albatrosses are known to have been captured in the 

mothership salmon fishery (DeGange and others, 1993; Ogi 

and others, 1993). For the land-based salmon fishery, there 

are two estimates of albatross bycatch, both indicating that 

only Laysan albatrosses were caught (table A1). The highest 

bycatch estimates for the Japanese land-based salmon fishery 

before 1977 were between 1,750–2,360 Laysan albatross per 

year (fig. A1). Fishing effort declined after 1977 and stopped 

in 1991 (fig. A2).

Fishing effort for the land-based salmon fishery 

was obtained from DeGange and Day (1991; fig. A2). 

Fishing effort was standardized into kilometers of net 

deployed (km-net) using the linear relation: km of net = 

12,762 + 14.053•Vessel-days (DeGange and Day, 1991). 

The last 4 years of the fishery’s operation (1988–91) were 

extrapolated under the assumption of a linear reduction in 

fishing effort from 1,156,224 tans (1 tan = 30–50 linear m of 

net) in 1987 to 536,674 tans in 1990, which is equivalent to 

34,686–57,811 km of net in 1987 to 16,100–26,833 km of net 

in 1990 (DeGange and Day, 1991; Ogi and others, 1993). The 

overall fishing effort is presented in figure A2.

Albatross bycatch rate estimates for the Japanese largemesh fishery are available only for 1990 (table A2). Likewise, 

fishing effort is only available for 1990 (Johnson and others, 

1993). Fishing effort for other years was estimated using an 

equivalence for 1990 (Number of Tans: Tunas caught) and the 

historical catch of tunas (albacore, skipjack, and other tunas) 

presented by Nakano and others (1993). Albatross bycatch 

by this fishery increased in 1981 as fishing effort increased 

(fig. A2). The estimated number of birds killed annually 

ranged from 1,300 to 2,500 for Laysan and 490–940 for blackfooted albatrosses from 1981 to 1990 (fig. A1).

10,000

15,000

0

5,000

20,000

25,000

30,000

NUMBER OF BIRDS CAUGHT

0

1,000

2,000

3,000

4,000

5,000

6,000

7,000

1970 1973 1976 1979 1982 1985 1988 1991 1994

Laysan albatross

Black-footed albatross 

TWDF

KOSQ

Total

JPSQ

JPLS

JPLM

TWDF

KOSQ

Total

JPSQ

JPLS

JPLM

Figure A1. Albatross bycatch estimates (± 1 SD) for the 

high-seas North Pacific driftnet fisheries: Japanese squid 

fishery (JPSQ), Japanese large-mesh fishery (JPLM), 

Japanese land-based salmon fishery (JPLS), Japanese 

mothership salmon fishery (JPMS), Korean squid fishery 

(KOSQ), and Taiwanese squid and tuna fishery (TWDF). See 

text for details.

Year sampled Laysan albatross 

(birds/km of net) Source

1977–87 Min = 0.00546

Max = 0.0071

SD = 0.0058

DeGange and Day (1991)1

1990 0.0121 Ogi and others (1993)

Overall mean Mean = 0.0082 

SD = 0.0068 

1

Estimated using Laysan albatross fraction (0.6 percent) of the total 

bycatch.

Table A1. Laysan albatross bycatch rate estimates for the 

Japanese land-based salmon fishery.

[km, kilometer; Min, minimum; Max, maximum; SD, standard deviation]
62 Status Assessment of Laysan and Black-Footed Albatrosses, North Pacific Ocean, 1923–2005

Albatross bycatch rate estimates for the Taiwanese 

driftnet fishery (includes both large-mesh gear for tuna and 

squid gear) for 1990 are presented in table A3. Estimates of 

total fishing effort (Number of Vessel-days) per year were 

based on the number of active vessels using the following 

equation: No. Vessel-days = 3,375.8•e0.0089•(no. vessels) 

(r2 = 0.784; data from Yeh and Tung, 1993). Fishing effort 

of the Taiwanese fleet increased rapidly from 1980 to 

1989, and decreased prior to the 1991 UN ban (fig. A2). 

Accordingly, the number of Laysan and black-footed 

albatrosses killed per year increased from 452 and 94 in 

1980, respectively, to a maximum of 2,119 Laysan and 438 

black-footed albatrosses in 1989 (fig. A1).

Bycatch estimates for the Japanese squid fleet are 

only available for 1990 (table A4). Total fishing effort 

from 1982 to 1990 is presented by Yatsu and others (1993). 

Fishing effort from 1978 to 1981 was estimated using data 

from 1982 to 1983 (Yatsu and others, 1993) and using 

the following relations between catch and effort: No. 

tans = 10,000,000 + 57.806•catch (tons). The Japanese 

fishing effort from 1978 to 1986 increased significantly 

from 516,652 km of net to 1,491,059 km of net (fig. A2). 

Accordingly, estimated bycatch of albatrosses peaked in 

1986 with an estimated 13,840 Laysan and 3,108 blackfooted albatrosses being killed (fig. A1).

Bycatch estimates for the Korean squid fleet are 

presented by Johnson and others (1993) and Ogi and others 

(1993) for 1990 only (table A5). Total fishing effort for 

1983–90 is presented by Gong and others (1993). Fishing 

effort for 1981–82 was estimated using the following 

relations between catch and effort: No. tans = -1,000,000 

+ 229.12•catch (tons), r2 = 0.747 (data from Gong and 

others, 1993, 1983–85 only). The Korean fishing effort 

began in 1981 and quickly increased to a maximum of 

1,239,016 km of net per year in 1989 (fig. A2). Albatross 

bycatch is assumed to correspond to this increase in effort, 

reaching an estimated maximum of 4,840–5,000 Laysan 

and 1,160–1,200 black-footed albatrosses killed per year 

from 1988 to 1992 (fig. A1).

Overall, these driftnet fisheries killed an estimated 

219,228 ± 32,116 Laysan and 50,311 ± 6,772 black-footed 

albatrosses (mean ± 1 SD) from 1978 to 1992, when it was 

closed by the UN ban (fig. A1). A disproportionately high 

number of juvenile albatrosses, primarily less than 2 years 

old, were caught in the squid and large-mesh driftnet 

fisheries (table A6). 

Figure A2. Fishing effort (km-net) for the main pelagic 

North Pacific driftnet fisheries that operated between 

1970 and 1992: Japanese squid fishery (JPSQ), Japanese 

large-mesh fishery (JPLM), Korean squid fishery (KOSQ), 

Japanese land-based salmon fishery (JPLS), and 

Taiwanese driftnet fishery (TWDF).

Year 

sampled

Laysan 

albatross 

(birds/km of net)

Black–footed 

albatross 

(birds/km of net)

Source

1990 0.0074–0.0185

(0.0004–0.0009)

0.0029–0.0073

(0.0002–0.0004)

Johnson and others 

(1993)

1990 0.0049–0.0122 0.0017–0.0042 Ogi and others (1993)

Overall 

mean

0.0061–0.0154

(0.0003–0.0008)

0.0023–0.0057

(0.0001–0.0003)

 

Table A2. Albatross bycatch rate estimates [mean (SD)] for the 

Japanese large-mesh driftnet fishery. 

[birds/km of net: 1 tan = 20–50 meters horizontal net length (Fitzgerald and 

others, 1993). km, kilometer]

0

400,000

800,000

1,200,000

1,600,000

1970 1973 1976 1979 1982 1985 1988 1991 1994

FISHING EFFORT, KM-NET

TWDF

KOSQ

JPSQ

JPLS

JPLM
Appendix A 63

Year 

sampled

Laysan 

albatross 

(birds/km of net)

Black–footed 

albatross 

(birds/km of net)

Source

1990 0.0030–0.0060

(0.0006–0.0012)

0.0006–0.0012

(0.0002–0.0004)

Johnson and others 

(1993)

1990 0.0020–0.0040 0.0004–0.0009 Ogi and others (1993)

Overall 

mean

0.0025–0.0050

(0.0005–0.0010)

0.0005–0.0010

(0.0002–0.0004)

 

Table A3. Albatross bycatch rate estimates [mean (SD)] for 

the Taiwanese driftnet fishery (large mesh and squid driftnet 

combined). 

[(birds/km of net): assuming 1 vessel-day about 800–1,200 tans (Ogi and 

others, 1993), and 1 tan about 30–40 meters (Fitzgerald and others, 1993). 

km, kilometer]

Year 

sampled

Laysan 

albatross 

(birds/km of net)

Black–footed 

albatross 

(birds/km of net)

Source

1990 0.0080–0.0138

(0.0003–0.0006)

0.0018–0.0031

(0.0001–0.0002)

Johnson and others (1993)

1990 0.0067–0.0116

(0.0008–0.0014)

0.0015–0.0026

(0.0002–0.0004)

Ogi and others (1993)

Overall 

mean

0.0073–0.0127

(0.0009–0.0016)

0.0016–0.0028

(0.0002–0.0004)

 

Table A4. Albatross bycatch rate estimates [mean (SD)] for the 

Japanese squid driftnet fishery. 

[(birds/km of net): 1 tan = 30–52 meters horizontal net length (Fitzgerald and 

others, 1993). km, kilometer]

Year 

sampled

Laysan 

albatross 

(birds/km of net)

Black-footed 

albatross 

(birds/km of net)

Source

1990 0.0039

(0.0003)

0.0009

(0.0001)

Johnson and others (1993)

1990 0.0042 0.0010 Ogi and others (1993)

Overall 

mean

0.0040

(0.0003)

0.0010

(0.0001)

 

Table A5. Albatross bycatch rate estimates [mean (SD)] for the 

Korean squid driftnet fishery. 

[(birds/km of net): 1 tan = 50 meters horizontal net length (Fitzgerald and 

others, 1993). km, kilometer]

Table A6. Sex and age distribution of Laysan and black-footed 

albatross carcasses salvaged from driftnet fisheries.

[<, less than; ♀, female; ♂, male; >, greater than] 

Age Broughton (1994) Langston and Rohwer (1995)1

Laysan albatross 

<2 years n = 8 (6 ♀, 2 ♂) n = 103 (52 ♀, 51 ♂)

2–6 years n = 1 (1 ♂) n = 34 (18 ♀, 16 ♂)

>6 years n = 1 (1 ♂) n = 54 (43 ♀, 11 ♂)

Black-footed albatross

<2 years n= 3 (1 ♀, 2 ♂) n = 65 (38 ♀, 27 ♂)

2–6 years n= 2 (1 ♀, 1 ♂) n = 16 ( 9 ♀, 7 ♂)

>6 years n= 3 (3 ♀) n = 36 (25 ♀, 11 ♂)

1

91 percent of birds were caught between June–October.
64 Status Assessment of Laysan and Black-Footed Albatrosses, North Pacific Ocean, 1923–2005

Area 2A Washington – California

Area 2B British Columbia

Area 2C SE Alaska

Area 3A Gulf of Alaska

Area 3B Alaska Peninsula

Area 4 Aleutian Islands

Total

FISHING EFFORT, IN 1,000 HOOKS

1970 1975 1980 1985 1990 1995 2000 2005

0

5,000

10,000

15,000

20,000

25,000

30,000

35,000

40,000

45,000

50,000

55,000

Survey

Interview

Laysan albatross Black-footed albatross

Survey

Interview

1970 1975 1980 1985 1990 1995 2000 2005 0

100

200

300

400

500

600

700

800

900

1,000

NUMBER OF BIRDS KILLED

Figure A4. Estimated albatross bycatch for the halibut fishery off the U.S. and Canada, based on fishery surveys and fishermen 

interviews (solid lines = means; dotted lines = 95-percent confidence interval for surveys).

Figure A3. Fishing effort for the halibut fishery off the U.S. and Canada (Source: IPHC). 

Demersal Longline Fisheries

A scientific observer program has monitored the Alaskan 

groundfish fisheries since 1993, and an assessment of seabird 

bycatch was recently published (National Marine Fisheries 

Service, 2006). Canada has a domestic longline fishery, mostly 

for rockfish, for which fishing effort and albatross bycatch is 

available from 1999 to 2002 (Smith and others, 2005; Smith 

and Morgan, 2005). 

Bycatch estimates for Laysan albatrosses are higher for 

longline fisheries operating in the Bering Sea and Aleutian 

Islands, and black-footed albatross bycatch rates are higher 

in the Gulf of Alaska (Boldt, 2004; National Marine Fisheries 

Service, 2006). These results are in agreement with the 

observed density of both species following fishing vessels 

in these regions (Melvin and others, 2004). When bycatch 

data did not affirm the albatross species caught, we followed 

Melvin and others (2004) and assumed that 62 percent of 

albatrosses caught in the Gulf of Alaska were black-footed 

albatrosses and 96 percent of albatrosses caught in the Bering 

Sea and Aleutian Islands were Laysan albatrosses (National 

Marine Fisheries Service, 2006). All bycatch off Washington 

and British Columbia were considered to be black-footed 

albatrosses (Smith and others, 2005).
Appendix A 65

Figure A5. Fishing effort and BPUE (birds per unit 

effort = bird/1,000 hooks) for the groundfish fishery 

conducted at the Bering Sea and Aleutian Islands 

(BSAI, A), the Gulf of Alaska (GOA, B), and the 

rockfish fishery off British Columbia (Rockfish, C). 

Confidence intervals (95 percent) are shown for the 

BPUE estimates.

tac_08_9354_0255_Albatrosses_FigA5

A

B

C

0

50,000

100,000

150,000

200,000

250,000

300,000

0.000

0.002

0.004

0.006

0.008

0.010

0.012

0

10,000

20,000

30,000

40,000

50,000

60,000

1992 1994 1996 1998 2000 2002 2004

0.000

0.005

0.010

0.015

0.020

0.025

0.030

0

1,000

2,000

3,000

4,000

5,000

6,000

0.000

0.020

0.040

0.060

0.080

0.100

0.120

0.140

0.160

FISHING EFFORT, IN 1,000 HOOKS

BIRDS PER UNIT EFFORT (BIRDS/1,000 HOOKS)

Laysan albatross

Black-footed albatross

Effort

Black-footed albatross,

stratified

Black-footed albatross,

traditional

Effort

Laysan

albatross

Black-footed

albatross

Effort

 The halibut fishery is managed by the International 

Pacific Halibut Commission (IPHC). Fishing effort for this 

fishery was obtained from the IPHC web page (http://www.

iphc.washington.edu/halcom/research/sa/sa.data/sa.data.html), 

except for British Columbia from 2000 to 2002, in which data 

were obtained from Smith and others (2005), and presented in 

figure A3. Albatross bycatch estimates are available only for 

1998 and 1999 for the Gulf of Alaska and Aleutians (Geernaert 

and others, 2001) and for 1999 to 2002 for British Columbia 

(Smith and others, 2005; Smith and Morgan, 2005). Given the 

lack of bycatch information, we used the mean of all estimates 

(table A7). The estimated number of albatrosses killed by U.S. 

and Canadian halibut fisheries has remained relatively low, 

with a maximum annual bycatch of 188 Laysan and 517 blackfooted albatrosses (fig. A4).

 The fishing effort at each fishing area, species bycatch 

rates, and estimates of total number of albatrosses killed are 

presented in figures A5 and A6. A former fishery off of British 

Columbia, which killed an estimated 7 and 4 black-footed 

albatrosses in 1999 and 2000 respectively, is included in 

figure A6. Data were not available at the time of this analysis 

to estimate bycatch of Laysan or black-footed albatrosses in 

demersal fisheries operating in the western Pacific.

Bycatch estimates for the Laysan albatross indicate 

a peak of 1,664 albatrosses killed in 1998, but significant 

decrease after this time, decreasing to 179 in 2003 (fig. A6). 

Likewise, a maximum estimate of 683 black-footed 

albatrosses were killed in 1996, but bycatch levels decreased 

to 176 in 2003 (fig. A6). This decrease is likely due to 

mitigation measures initiated in 1997 (see below) that kept 

bycatch low despite an increase in fishing effort (fig. A5).

 In the Alaska region, new seabird avoidance regulations 

have been in force since February 2004, although regional 

initiatives for reducing seabird bycatch began in 1997 

(National Marine Fisheries Service-Alaska, www.fakr.noaa.

gov/protectedresources/seabirds/bycatchinfo.htm#tra). The 

bycatch rate significantly decreased following implementation 

of these measures (fig. A5). Canada started an observer 

program in January 2000, and since 2002, there have been 

mandatory mitigation measures for halibut and rockfish 

fisheries in British Columbia along with the requirement to 

have scientific observers onboard when requested (J. Smith, 

University of Washington, written commun., 2005). 

Accordingly, albatross bycatch rates are expected to be further 

reduced.
66 Status Assessment of Laysan and Black-Footed Albatrosses, North Pacific Ocean, 1923–2005

tac_08_9354_0255_Albatrosses_FigA6

0

500

1,000

1,500

2,000

2,500

1992 1994 1996 1998 2000 2002 2004

NUMBER OF BIRDS KILLED

BSAI

Total

Total

GOA

BSAI

GOA

Black-footed albatross

Rockfish

Laysan albatross

Figure A6. Overall number of albatrosses killed in the groundfish fisheries operating at the Bering Sea and Aleutian 

Islands (BSAI), Gulf of Alaska (GOA), and British Columbia (Rockfish). Confidence intervals (95 percent) are shown for 

totals only.

Bycatch estimates Surveys Interview Number of 

years sampled

Area 2A Washington - California & 2B British Columbia 1 0.0327 ± 0.0299 2 0.0049 ± 0.0021 2 5

Area 2C SE Alaska 0.0031 ± 0.0043 0 2

Area 3A Gulf of Alaska 0.0009 ± 0.0013 0.0006 ± 0.0008 2

Area 3B Alaska Peninsula 0.0032 ± 0.0045 0.0004 ± 0.0001 2

Area 4 Aleutian Islands 0.0323 ± 0.0456 0 2

1

 Bycatch has not been estimated off of Washington so it was assumed to be the same rate as reported for British Columbia (BC); 2‘surveys’ in Area 2B (BC) 

are data from fishery observers onboard vessels, and ‘interview’ corresponds to a stratified estimation of bycatch rates considering the distribution of fishing 

effort and of the albatrosses being caught (Smith and others, 2005). 

2

 Data obtained from fisher’s master information at landing.

Table A7. Albatross (Laysan and black-footed combined) bycatch estimates (birds/1,000 hooks) for the halibut fishery off the U.S. and 

Canada (mean ± 1 SD), based on observer surveys or fishermen logbooks (interview). 

[From Geernaert and others (2001). Surveys: Data obtained from scientific observers from survey fishing trips. Interview: Data obtained from fisher’s master 

information at landing]
Appendix A 67

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

0.90

1.00

1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005

PROPORTION

OFP-Tuna

OFP-Swordfish

HI-Tuna

HI-Swordfish

Figure A8. Proportion of total catch that was tunas (OFP-Tuna) or swordfish (OFP-Swordfish) as reported to the OFP, and the 

proportion of fishing effort allocated by the Hawai`i-based fleet for tuna (HI-Tuna) or swordfish (HI-Swordfish) exclusively 

(mixed trips excluded). (Sources: Kinan 2003a, 2003b, 2004; National Marine Fisheries Service, 2005).

Figure A7. Total fishing effort of pelagic longline 

fisheries in the North Pacific Ocean (north of 20°N) 

reported to the OFP.

tac_08_9354_0255_Albatrosses_FigA7

0

50,000

100,000

150,000

1950 1960 1970 1985 1990 2000 1955 1965 1975 1980 1995 2005

FISHING EFFORT, IN 1,000 HOOKS

Pelagic Longline Fisheries

Bycatch estimates were calculated using the annual 

bycatch rate estimated for the Hawaiian-based pelagic longline 

fishery (1994–2000) and the total, pooled fishing effort 

reported by the Ocean Fisheries Program (OFP (as Lewison 

and Crowder, 2003). We included only fishing effort north 

of 20°N (as Hyrenbach and Dotson, 2003) because most 

albatross interactions occurred north of 20°N (U.S. Fish and 

Wildlife Service, 2004b) and telemetry studies indicate that 

breeding adults do not travel south of 20°N (Fernández and 

others, 2001).

 The International fishing effort reported by the OFP 

(fig. A7) is not divided into swordfish and tunas, which have 

significantly different albatross bycatch rates. However, they 

do report total catch of swordfish and tunas, which we used 

as an index for the relative fishing effort allocated to each 

(fig. A8). The analysis of the Hawaiian pelagic longline fleet 

suggests two alternative bycatch rate scenarios differing in 

bycatch level. Here we follow the lower bycatch rate scenario 

(Hypothesis 1 or H1), and consider the catch reports for tuna 

and swordfish from the OFP relative to the Hawaiian fleet 

during the late 1990s (fig. A8). In addition, we used a higher 

bycatch rate scenario (Hypothesis 2 or H2) in our population 

models. The estimated bycatch rates are presented in table A8. 

Results from our matrix models supported the lower bycatch 

rate scenario. Lewison and Crowder (2003) provide the only 

other bycatch rate estimate for this fishery. They used a ratio 

of 80:20 for tuna:swordfish fishing effort, which produced 

an overall bycatch rate for black-footed albatrosses of 0.088, 

similar to our combined H1 estimate of about 0.073 (0.050–

0.116) for the late 1990s.

The fishing effort reached peaks of 147 and 149 million 

hooks per year in 1960 and 1967, respectively. This effort 

decreased during the 1970s and increased again in 1981 

to 121 million hooks per year. Since 1981, there has been 

a decreasing trend in number of hooks deployed (fig. A7). 

Accordingly, the estimated bycatch for Laysan albatrosses has 

fluctuated from 5,600 albatrosses in 1961 to 1,290 in 2005, 

under the assumptions of H1 (fig. A9). Similarly, the estimated 

mortality of black-footed albatrosses peaked with 15,290 in 

1961 and again in the early 1980s with 10,200 albatrosses. 

The estimated bycatch has decreased since then to 4,800 

albatrosses per year in accordance with H1 (fig. A9).
68 Status Assessment of Laysan and Black-Footed Albatrosses, North Pacific Ocean, 1923–2005

Unlike other studies, we did not stratify the data by 

sectors or seasons because: (1) fishing vessels and seabirds 

both use highly productive waters, such as frontal zones (that 

is, Polovina and others, 2001; Seki and others, 2002) and thus, 

the distributions of vessels and birds are likely associated (as 

suggested from band recoveries; Fisher and Fisher, 1972); 

(2) even when a portion of the population is breeding and 

at the colony, the remainder of the population is widely 

dispersed; (3) and albatrosses are prone to approach fishing 

vessels, particularly in regions of low productivity.

 Catch and fishing effort data reported to the OFP is 

incomplete. According to the OFP, available data north of 

20°N include Japan (since 1950), Taiwan (since 1967), and 

the U.S. (since 1991). Gilman and others (2005) mentioned 

that China also has a pelagic longline fleet in the North Pacific 

Ocean, although it is unclear if they fish north of 20°N.

Black-footed, H1

Black-footed, H2

Laysan, H1 

Laysan, H2

Estimated albatrosses killed—solid lines = means; 

dashed lines = 95-percent confidence interval

0

10,000

20,000

30,000

40,000

50,000

60,000

70,000

NUMBER OF BIRDS KILLED

1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005

Figure A9. Estimates of the total number of Laysan and black-footed albatross killed by the International North Pacific pelagic 

longline fishery under two bycatch rate hypotheses.

Species Hypothesis

Swordfish

 

Tuna Overall

Mean 95% CI N (sets) Mean 95% CI N (sets) Mean 95% CI

BFAL H1 0.329 0.241 – 0.463 612 0.046 0.028 – 0.082 901 0.073 0.050 – 0.116

H2 0.388 0.301 – 0.511 931 0.197 0.121 – 0.352 579 0.208 0.131 – 0.361

LAAL H1 0.156 0.098 – 0.266 612 0.006 0.003 – 0.013 901 0.027 0.019 – 0.042

H2 0.270 0.199 – 0.377 931 0.190 0.099 – 0.430 579 0.187 0.099 – 0.417

Table A8. A comparison of bycatch rates (birds/1000 hooks) for black-footed (BFAL) and Laysan (LAAL) albatrosses under two 

alternative hypotheses.

[H1 = low rate, H2 = high rate; %, percent; Cl, confidence interval]

Here we describe our assessment of the bycatch rate of 

the Hawaiian pelagic longline fleet targeting swordfish and 

tuna, and how we used it to estimate overall mortality due to 

the International pelagic longline fleet in the North Pacific 

Ocean. Results from the Hawaiian scientific observer program 

indicate that fishing gear targeting swordfish (shallow sets; 

about 40 m; Kinan, 2003a) and tuna (deep sets; about 100–400 

m; Kinan, 2003a) differ significantly in seabird bycatch 

rates, with shallow swordfish sets catching more albatrosses 

(Lewison and Crowder, 2003). This is likely a function of 

shallower sets taking longer to sink, making baited hooks 

available to scavenging birds for a longer period of time. 

Although some sets for tuna also are shallow, classifying these 

is not straightforward, especially for the early years of the 

scientific observer program. As the OFP only provides overall 

catches of swordfish and tuna, only these two categories were 

considered.
Appendix A 69

Data collected by the Hawaiian scientific observer 

program, 1994–2004, were provided through the NOAA 

Fisheries Department, Honolulu, Hawai`i. Only sets deployed 

north of 20oN were used because this represents the area with 

most of the albatross-fisheries interactions (U.S. Fish and 

Wildlife Service, 2004b), as supported by telemetry studies 

(fig. 2; Fernández and others, 2001; BirdLife International, 

2004c). Bycatch per unit effort (BPUE, birds per 1,000 

hooks) estimates were made by fitting a negative binomial 

distribution to the BPUE data using set-by-set estimates. This 

probability distribution proved to have the best fit to the data, 

which is highly skewed and has many zero-values. Dead 

and injured birds hauled onboard were used for estimating 

the BPUE. Injured birds were included in estimates because 

they probably would be seriously injured on vessels without 

observers. Including these birds may compensate for birds 

caught during setting but lost before hauling (Gilman and 

others, 2005). Spatial and temporal patterns in the BPUE were 

analyzed using the level of detail associated with the data 

(month, latitude [x 5o] and longitude [x 5o]). Data were pooled 

into 2-month intervals, as well as latitudinal and longitudinal 

classes, to increase sample sizes for analysis. BPUE was not 

estimated for sample sizes less than 10 sets.

The temporal pattern and magnitude of bycatch, stratified 

by target species, were similar for black-footed and Laysan 

albatrosses. Results indicated that different bycatch rates for 

sets targeting swordfish compared to other species, generically 

called tunas (fig. A10). Sets targeting tunas had markedly 

lower bycatch across the years considered, whereas bycatch 

rate for sets targeting swordfish were high from 1994 to 

2001, when this fishery was closed in Hawai`i (April 2001, 

emergency rule 66 FR 31561, ratified in June 2002 through 

the C.M. 67FR40232).

For black-footed albatrosses, the proportion of birds 

recorded as ‘injured’ remained similar between years, mean 

= 20.9 percent, SD = 2.2 percent (1994–97). This estimate is 

lower than the 28 to 34 percent of birds caught during setting 

but lost before hauling (in Gilman and others, 2005). Even 

if these birds were included, the calculated bycatch is still 

probably an underestimate of the actual bycatch.

The temporal and spatial patterns in black-footed 

albatross bycatch rate for sets targeting swordfish and tunas 

were examined from 1994 to 1996. Data from these years 

were pooled due to low sample sizes. Bycatch rate estimates 

were higher for the area north of the Hawaiian Islands, within 

25o–29oN and 165o–174oW. No other temporal or spatial 

patterns were detected (fig. A11). This area is only used by 

U.S. fleets. The U.S. fleet does not fish in the western North 

Pacific, where a significant amount of fishing for swordfish 

occurs (Saito and Yokawa, 2000), and black-footed albatrosses 

forage (Robbins and Rice, 1974; Hyrenbach and others, 

2005). The overall bycatch rate was estimated assuming no 

geographic variation.

tac_08_9354_0255_Albatrosses_FigA10

Black-footed albatross

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1.1

1.2

1.3

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1.1

1.2

1.3

0

200

400

600

800

1,000

1,200

1,400

0

200

400

600

800

1,000

1,200

1,400

PELAGIC LONGLINE FISHERY IN NUMBER OF SETS OBSERVED

Laysan albatross

1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005

BYCATCH ESTIMATE, IN BIRDS PER UNIT EFFORT (BIRDS/1,000 HOOKS)

Swordfish

Swordfish

Total

Tunas

Tunas

Pelagic longline fishery

EXPLANATION

Bycatch estimates

A.

B.

Figure A10. Black-footed (A) and Laysan albatross (B) 

bycatch estimates (BPUE, birds per 1,000 hooks; mean 

and 95-percent confidence interval) and sample sizes 

(number of sets observed; solid lines) for the pelagic 

longline fishery based in Hawai`i. Data are from the 

scientific observer program.
70 Status Assessment of Laysan and Black-Footed Albatrosses, North Pacific Ocean, 1923–2005

tac_08_9354_0255_Albatrosses_FigA11

NUMBER OF SETS

BIRDS PER UNIT EFFORT (BIRDS/1,000 HOOKS)

NUMBER OF SETSNUMBER OF SETS

NUMBER OF SETSNUMBER OF SETS

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0

50

100

150

200

250

300

JAN-FEB MAR-APR MAY-JUNE JULY-AUG SEPT-OCT NOV-DEC

NUMBER OF SETS

BIRDS PER UNIT EFFORT (BIRDS/1,000 HOOKS)

0.0

0.5

1.0

1.5

2.0

2.5

3.0

BIRDS PER UNIT EFFORT (BIRDS/1,000 HOOKS)

0.0

0.5

1.0

1.5

2.0

2.5

3.0

BIRDS PER UNIT EFFORT (BIRDS/1,000 HOOKS)

0.0

0.5

1.0

1.5

2.0

2.5

3.0

BIRDS PER UNIT EFFORT (BIRDS/1,000 HOOKS)

0.0

0.5

1.0

1.5

2.0

2.5

3.0

BIRDS PER UNIT EFFORT (BIRDS/1,000 HOOKS)

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0

50

100

150

200

250

300

JAN-FEB MAR-APR MAY-JUNE JULY-AUG SEPT-OCT NOV-DEC

20N 25N 30N 35N 40N

0

50

100

150

200

250

300

350

400

450

20N 25N 30N 35N 40N

0

50

100

150

200

250

300

350

400

450

170W 165W 160W 155W 150W 145W

0

50

100

150

200

250

175W170E125W140W170W 165W 160W 155W 150W 145W

0

50

100

150

200

250

175W170E125W140W

Swordfish

Swordfish

Tunas

Species other than

swordfish

Sets targeting:

Bycatch estimates

Figure A11. Black-footed albatross (BFAL, left) and Laysan albatross (LAAL, right) bycatch rate estimates (BPUE, birds 

per 1000 hooks; mean and 95-percent confidence interval) and sample sizes (number of sets observed; solid line) for the 

pelagic longline fishery based in Hawai`i from 1994 to1996 (data pooled). Estimates are grouped by month (top), latitude 

(middle), and longitude (bottom). Data are from the scientific observer program. 
Appendix A 71

There was a significantly lower black-footed albatross 

bycatch rate for sets targeting tuna from 1997 to 2000 

compared to 1994 to 1996 (fig. A10). This difference probably 

is the result of a better classification of swordfish and tuna sets 

after 1996, because bycatch in sets targeting swordfish were 

similar over this period, and no official mitigation measures 

were implemented until 2000. We considered the bycatch rate 

for 1994–96 and 1997–2000 as alternative hypotheses (H1 

and H2, respectively) for the bycatch rate of the International 

fleet. Although fishing effort directed at swordfish or tunas 

is unknown for the International fleet, we used the reported 

number of swordfish and tunas caught as an index of the 

fishing effort expended for each target species. H1 may occur 

if fishing effort oriented to swordfish or shallow sets is underreported, whereas H2 may occur if the International fleet has 

a similar proportion of fishing effort for tuna and swordfish 

compared to the Hawaiian fleet during 1997–2000 (fig. A8, 

table A8).

Finally, we used the proportion of tuna to swordfish 

caught each year (fig. A8) to estimate the mean bycatch rate 

for the fleet. As a reference, this proportion over the last 

10 years was 92:8, yielding overall bycatch rates of H1: 0.073 

and H2: 0.208 (table A8). The overall bycatch rate estimated 

using H2 is similar to that estimated by Lewison and Crowder 

(2003), the only other estimate available for the fleet.

The proportion of Laysan albatrosses recorded as 

‘injured’ remained similar between years (1994–97), with a 

mean of 25.5 percent (SD = 8.3) and is lower than the 28 to 34 

percent loss rate estimated by Gilman and others (2005). Thus, 

inclusion of these birds is not likely to inflate our bycatch rate 

estimates.

The temporal and spatial patterns in bycatch rates for sets 

targeting swordfish and tunas were examined for 1994–96. 

Data from these years were pooled due to the small sample 

sizes. Bycatch rate estimates were higher for the area north 

of the Hawaiian Islands, within 25o–29oN and 165o–174oW, 

and during March–June (fig. A11). This suggests an important 

temporal-spatial effect that corresponds to the chick-rearing 

period in the NWHI. This area is only used by U.S. fleets. The 

U.S. fleet does not fish in the western North Pacific, an area 

important to albatrosses, especially young Laysan albatrosses 

(fig. 2; Fisher and Fisher, 1972; Robbins and Rice, 1974), but 

the International fleet does, and the bycatch rate is unknown.

 There was a significant decline in the Laysan albatross 

bycatch rate for sets targeting tuna between 1994–96 and 

1997–2000 (fig. A10). This may be the result of a better 

classification of swordfish and tuna sets after 1996, because 

the bycatch rate for sets targeting swordfish remained 

relatively constant over the entire period. Because fishing 

effort directed toward swordfish and tunas is unknown for the 

International fleet, we considered two alternative hypotheses 

regarding the bycatch rate for the International fleet: H1, the 

rate for 1994–96 and; H2, the rate for 1997–2000 (table A8). 

We used the proportion of tunas to swordfish caught each year 

(fig. A8) to obtain a weighted mean of the bycatch rate for the 

fleet. As a reference, this proportion over the last 10 years has 

been 92:8, yielding an overall bycatch rate of H1 = 0.027 and 

H2 = 0.187 (table A8).

Trawl Fisheries

Albatross bycatch has been recorded in the Alaskan trawl 

fisheries, but monitoring trawl bycatch is limited to birds 

captured in the nets. Birds killed or injured upon striking the 

cables (warps) or the sensor wire (3rd wire) are not recorded 

unless they fall into the water and are captured in the net. 

However, cable strike information began to be collected in 

2004. As of 2005, no albatrosses have been reported as being 

killed by cables or sensor wires. Canada and the U.S. have 

trawl fisheries off British Columbia, Washington, Oregon, and 

California, but no albatross bycatch data are available from 

these fisheries.
72 Status Assessment of Laysan and Black-Footed Albatrosses, North Pacific Ocean, 1923–2005

This page left intentionally blank
Appendix B 73

Appendix B. Descriptions and History of the 

Northwestern Hawaiian Islands

The Northwestern Hawaiian Islands have undergone a 

series of physical changes during the past century as a result of 

human occupation. To understand the effect of these changes 

Island Parameter estimation

Kure (1923-1956): â = 0.0811; = 500; SD = 14

(1957-2005): â = 0.1713; Kˆ = 4,493; SD = 447

Midway1

â = 0.1084; Kˆ = 446,779; SD = 53,542

Pearl & Hermes North Island:

Mean = 787; SD = 140 (just 3 censuses in 1963-1967)

Southeast Island: â = 0.1118; Kˆ = 13,926; SD = 4,691

Grass Island: EST1: â = 0.072; Kˆ = 1,799; SD = 520

EST2: â = 0.12; Kˆ = 875; SD = 440

Kittery Island: Mean = 25; SD = 28 (just 5 censuses in 1963-1969)

Seal Island: â = 0.0953; Kˆ = 206; SD = 150

Total K= 15,819

Lisianski â = 0.0661; Kˆ = 31,074; SD = 9,574

Laysan â = 0.0607; Kˆ = 198,926; SD = 53,669

Gardner Pinnacles â = 0.06; Kˆ = 8; SD = 6

French Frigate Shoals Tern Island (1954–2005): â = 0.1282; Kˆ = 2,048; SD = 260

East Island (1950–2005): â = 0.1373; Kˆ = 733; SD = 168

Other islands: (1923–1990): â = 0.1; Kˆ = 228; SD = 85

(1991–2005): â = 0.1; Kˆ = 41; SD = 45

Necker â = -0.0076; Kˆ = NA (exponential model); SD = 752

Nihoa â = 0.0401; Kˆ = 300; SD= 221

Ni`ihau Mean = 338; SD = 230 (just 2 censuses)

Kaua`i â = 0.0968; Kˆ = 225; SD = 41

O`ahu â = 0.0968; Kˆ = 10; SD = 5

Mexico Guadalupe Island:

â = 0.1693; Kˆ = NA (exponential model); SD= 11

San Benedicto Island:

â = 0.0747; Kˆ = 10; SD = 2

1

 Includes known Navy reduction of Laysan albatross breeding pairs (table 2).

Table B1. Parameter estimation for Laysan albatross breeding population size at each island. 

[Logistic model fitted: (1 )

+1= t a - N / K N N e t t  , where Nt

 = number of breeding pairs at time t, Nt+1 = number of breeding 

pairs at time t+1, a = population growth rate, K = carrying capacity, and e = 2.718, the base of the natural logarithm]

Kˆ

on the population size of both albatross species (tables B1 and 

B2), we present a detailed account for each breeding island 

below.
74 Status Assessment of Laysan and Black-Footed Albatrosses, North Pacific Ocean, 1923–2005

Island Parameter estimation

Kure (1923-1957): â = -0.0544; Kˆ = NA (exponential model); SD = 8 

(1957-2005): â = 0.0869; Kˆ = 3,994; SD = 228

Midway1

Midway-H1: (1923-1955) â = 0.0473; Kˆ = 28,023; SD = 0 (CV5% used) 

(1955-1964): â = -0.0810; Kˆ = NA (exp. model); SD = 1,520 

(1964-2005): â = 0.0992; Kˆ = 21,943; SD = 1,373 

Midway-H2: (1923-1945) â = 0.1201; Kˆ = 27,920; SD = 0 (CV5% used) 

(1945-1964): â = -0.0678; Kˆ = NA (exp. model); SD = 1,348 

(1964-2005): â = 0.0992; Kˆ = 21,943; SD = 1,373

Pearl & Hermes North Island: EST1: â = 0.072; Kˆ = 1,851; SD = 504 

EST2: â = 0.0416; Kˆ = 3,000; SD = 457 

Southeast Island: â = 0.0953; Kˆ = 3,425; SD = 1,131 

Grass Island: â = 0.0538; Kˆ = 1,933; SD = 466 

Kittery Island: Mean = 335; SD = 127 (just 6 censuses in 1957-1968) 

Seal Island: EST1: â = -0.0319; Kˆ = NA (exp. model); SD = 146 

EST2: â = 0.0397; Kˆ = 279; SD = 142 

Total K = 7,823 or 8,972.

Lisianski â = 0.0953; Kˆ = 2,866; SD = 732

Laysan EST1 (1923-2005): â = 0.0905; Kˆ = 39,030; SD = 462 

EST2 (1958-2005): â = 0.0953; Kˆ = 18,095; SD = 4,630 

EST3 (1923-2005): â = 0.0549; Kˆ = 21,681; SD = 2,655

French Frigate 

Shoals Tern Island: (1923-1942): â = 0.0953; Kˆ = NA (exp. model); SD = NA

(1943-1979): â = 0.0953; Kˆ = NA (exponential model); SD = 14 

(1979-2005): â = 0.2479; Kˆ = 1,585; SD = 97 

East Island: (1954-2005): â = 0.1825; Kˆ = 2,009; SD = 228 

Other islands: (1923-1990): â = 0.0953; Kˆ = 1,512; SD = 451 

(1990-2005): â = 0.0953; Kˆ = 288; SD = 237

Necker â = 0.0953; Kˆ = 214; SD = 101

Nihoa â = -0.0166; Kˆ = NA (exponential model); SD = 23

JAPAN Izu Shoto: (1957-2005): â = 0.1307; Kˆ = 2,009; SD = 79 

Senkaku Retto: (1973-2005): â = 0.1199; Kˆ = NA (exp. model); SD = 8 

Ogasawara Gunto: (1950-2005): â = 0.0953; Kˆ = NA (exp. model); 

SD = NA

1

 Includes known Navy reduction of black-footed albatross breeding pairs (table 2).

Table B2. Parameter estimation for black-footed albatross breeding population size at each island. 

[Logistic model fitted: (1 )

+1= t a - N / K N N e t t  , where Nt

 = number of breeding pairs at time t, Nt+1 = number of breeding 

pairs at time t+1, a = population growth rate, K = carrying capacity, and e = 2.718, the base of the natural logarithm. %, 

percent]
Appendix B 75

Kure Atoll

Kure (28°25′N, 178°10′W) is a low, coral atoll containing 

Green Island (100 ha), the only permanent land in the atoll. 

Low (less than 7.5 m) dunes are present on the northern shore 

of the island, and high waves during winter storms may wash 

beaches up to the vegetation border, thus destroying blackfooted albatross nests. Dense vegetation, primarily Scaevola 

taccada, covers most of the island, except near beaches and 

areas cleared for the LORAN Station. This dense vegetation 

greatly reduces potential albatross nesting habitat. In 1960, the 

U.S. Coast Guard built a 1,200-m runway and a 188-m high 

LORAN tower on the central plain of the island (Woodward, 

1972). In 1992, the U.S. Coast Guard left the island and 

removed all equipment. Since 1992 the island has been 

managed by the State of Hawai`i as a seabird sanctuary. 

Midway Atoll

This low, coral atoll (28°14′N, 177°22′W) contains 

two large islands, Sand (435 ha) and Eastern (135 ha), and 

two small islands, the Spit islands. The islands have been 

greatly modified by humans since the early 1900s, first by 

the Commercial Pacific Cable Company (1903), then by 

Pan American Airways (1935), the U.S. Navy (1941), and 

finally the U.S. Fish and Wildlife Service (1997). The greatest 

change has been the increase in land area, especially on Sand 

Island. The cable company transported barge loads of topsoil 

to the atoll from the main Hawaiian Islands, and the military 

deposited dredge spoils from the lagoon. The introduction of 

non-native grasses and trees soon after occupation in 1903 

greatly improved nesting habitat for the Laysan albatross 

(Rice and Kenyon, 1962a). During WW II, the U.S. Navy 

used Midway Atoll as an air station, building runways on both 

Sand and Eastern Islands. A considerable fraction of nesting 

habitat was usurped for buildings and runways (Fisher, 1949). 

In 1993, the Midway Naval Air Station was operationally 

closed and environmental clean-up began. The last Navy 

personnel left in 1997 soon after jurisdiction of the atoll was 

transferred to USFWS. Since 1996, the USFWS has overseen 

the removal of many of the former buildings and restoration 

of extensive areas once covered with asphalt (Tickell, 2000). 

Golden crown-beard, an invasive woody herb, is widespread 

and degrades seabird nesting habitat.

Pearl and Hermes Reef

This atoll (27°44′–27°57′N, 175°43′–175°59′W) consists 

of seven persistent, small, sand islands, totaling approximately 

34 ha of emergent land. The five largest islets, Southeast 

Grass, Seal-Kittery, North, and Little North support a limited 

flora, and the two smallest islets (Sand and Bird) are sand bars 

without vegetation (Baker and others, 2006). Rabbits were 

first documented on Southeast Island in 1916 and eradicated 

in 1928 (Amerson and others, 1974). Native bunch grass 

vegetation has been replaced in many areas by herbaceous 

creeping vegetation and the invasive weed, golden crownbeard, that limits albatross nesting habitat.

Lisianski Island

This is a 180-ha coral island (26°02′N, 174°00′W) with 

only a small area of sandy beaches. The east coast has exposed 

reef rock, and elsewhere the beaches are relatively narrow, 

except for the southern end where black-footed albatrosses 

commonly nest (Clapp and Wirtz, 1975). Dunes along the 

shorelines are 3–6 m as above sea level, and their edges are 

covered with dense patches of Scaevola sp. The primary plant 

species of the island interior are bunchgrass (Eragrostis sp.), 

scattered ironwood and coconut trees, and a small grove 

of devils-claw (Pisonia grandis). Birds on the island were 

harvested by feather hunters in 1904 and 1909. Rabbits were 

introduced early in the 20th century and died of starvation in 

1915 after consuming all edible vegetation on the island. In 

the absence of rabbits, the vegetation has recovered (Clapp 

and Wirtz, 1975).

Laysan Island

This is a large, roughly rectangular, sand island (291 ha; 

25°42′N, 171°44′W) with a hypersaline lake at its center. 

The island has a maximum height of 12 m above sea level, 

with coastal dunes rising abruptly from the sea to 4.5–5.4 m. 

Except for the shoreline, most of the island is covered by 

vegetation: Scaevola sp. on dune borders and scattered bunchgrass (Eragrostis sp.) in the interior. Laysan Island has wide, 

sandy beaches (225–360 m in width), except along the west 

side (22.5–45.0 m in width). Guano was mined from 1891 

to 1903 and the “guano hardpan”, the primary excavation 

site at the south end of the island, is still a prominent feature. 

Rabbits were introduced about 1903 and destroyed most of the 

vegetation before being eradicated in 1923 (Ely and Clapp, 

1973). Birds on the island were killed by feather hunters from 

1908 to 1910, and again in 1915.
76 Status Assessment of Laysan and Black-Footed Albatrosses, North Pacific Ocean, 1923–2005

Gardner Pinnacles 

The Gardner Pinnacles (25°00′N, 167°55′W) consists of 

two small volcanic rocks, 58 m high and 30 m high, totaling 

1.2 ha in area. The islets have steep sides and no sand beaches 

(Harrison, 1990).

French Frigate Shoals

The atoll (23°37′–23°52′N, 166°03′–166°20′W) consists 

of 12 low, sandy islands with sparse vegetation, and a pair 

of volcanic rock islands (36.6 and 2.7 m high) known as 

La Perouse Pinnacle. In total, the islands consist of 45 ha of 

land, and only East, Tern, and Trig Islands support vegetation 

and are not regularly washed over by storm waves. Most of 

the islands are 2.4–3.6 m above sea level and have changed 

shape and size in recent history (Amerson, 1971). Tern Island, 

formerly a small, sandy island (4.4 ha), was transformed into 

a runway by the U.S. Navy in 1942 and now has an area of 

22.7 ha. From 1952 to 1979, a U.S. Coast Guard LORAN 

Station operated on Tern Island. East Island is sandy, 4.5 ha in 

size, and has one-half of its area covered by vegetation. U.S. 

military personnel first occupied East Island in 1935, living 

in a tent camp. In 1944, the U.S. Coast Guard established a 

LORAN Station on East Island, which remained in operation 

until it moved to Tern Island in 1952. Whale-Skate originally 

consisted of two islands (6.7 ha) that later connected by a sand 

isthmus. During the 1990s, Whale-Skate slowly eroded until 

it completely disappeared in 1997. Trig Island is 4.0 ha in size 

and half-covered with vegetation. Little Gin Island is 2.0 ha in 

size and lacks vegetation. 

Necker Island

This high, rocky island (23°35′N, 164°42′W) is 16.4 ha 

in size, with steep sides rising 46.8–82.8 m above sea level. 

The limited vegetation on the island is composed primarily of 

Chenopodium sp. and Portulaca sp. Albatrosses nest on the 

hill tops and higher slopes (Clapp and Kridler, 1977).

Nihoa

This high, rocky island (23°06′N, 161°58′W) is 62.4 ha 

in size, with high peaks (107–267 m above sea level), welldeveloped valleys, steep cliffs, and a single sand beach. Nihoa 

is well-vegetated by grasses (Eragrostis sp.) and shrubs (Sida 

fallax, Chenopodium oahuensis, Sesbania tomentosa; Clapp 

and others, 1977). An introduced grasshopper (Schistocerca 

nitens) was first reported in the 1980s and during periodic 

population outbreaks the grasshoppers consume much of the 

island’s vegetation.
Appendix C 77

Appendix C. Detailed Methods for Analysis of Population 

Trends and Bycatch Impacts

Regression Analyses

We used linear regression to fit log-transformed counts of 

breeding pairs from Midway Atoll, Laysan Island, and French 

Frigate Shoals combined from 1923 to 2005, 1957 to 2005, 

and 1992 to 2005. Laysan albatross counts were available 

from the three island groups for 8 years (1923, 1957, 1992, 

1997, 2001, 2002, 2004, and 2005). Black-footed albatross 

counts were available from the three island groups for 11 years 

(1923, 1957, 1992, and 1998–2005). Analyses in which the 

p-value was less than or equal to 0.05 were taken as significant 

and evidence that the population had either increased or 

decreased over the time interval. 

Population Viability Analyses (PVA)

Logistic and exponential models were fit to the nest pair 

data, and these models were used to project population change 

60 years (about three generations) into the future to assess 

population viability. 

Breeding population trajectories were analyzed using the 

following stochastic, discrete-time, logistic model (Dennis and 

Taper, 1994):

1 ,

where: 

is defined as ln( ), 

is defined as growth rate, 

is defined as density-dependent parameter, 

is defined as standard deviation of the 

process stochasticity, and 

~ 

Xt X X a be Z t t t

X N

a

b

Z

σ

σ

+ = + + +

normal (0,1). 

 (1)

As Xt+1 – Xt = Rt , the former equation becomes a nonlinear autoregressive model of the R-function (Berryman, 

2003) with mean E(RT) = a + beXt and environmental 

stochasticity given by σZt , considering demographic 

stochasticity is absent given the large population sizes (figs. 6 

and 14). This model allows the testing of nested hypotheses 

regarding the nature of the population dynamics: Hypothesis 1 

(H1): a≠0, b=0 and; Hypothesis 2 (H2): a≠0, b<0. H1 describes 

an exponential growth model with environmental stochasticity, 

and H2 describes a stochastic Ricker model with first-order 

negative feedback on population size (Dennis and Taper, 

1994). For all purposes, nest counts were assumed to be 

representative of the breeding female population, from which 

Robst

 = ln(Nt+1 / Nt), the observed growth rate, was obtained.

Parameter estimation was conducted by maximizing 

the negative log-likelihood function L(â, ˆ

b, 2 σˆ ). Although 

the estimations of â, ˆ

b, 2 σˆ are unbiased, Dennis and Taper 

(1994) recommend using parametric bootstrapping for 

estimating confidence intervals given they are not statistically 

independent from each other. Accordingly, 2,000 population 

projections with the same length and initial population size as 

the original data were generated using eq. 1 and the 

original L(â, ˆ

b, 2 σˆ ) values. For each generated series, new 

L(âi*, ˆ

i b *, 2 ˆσ i *) were estimated and used to obtain confidence 

intervals for each parameter (2.5 and 97.5 percent sampling 

percentiles).

For the exponential model, simple linear methods 

were used for confidence interval estimation (Dennis and 

others, 1991). Accordingly, the confidence interval for â was 

estimated using (â – tα,q–1•SE, â + tα,q–1•SE), with α = 0.05, 

q = no. of Robs points, and the confidence interval for 2 σˆ

estimated as ((q–1)σ2/ x2

0.025, q–1 , (q-1)σ2

 / x2

0.975, q–1) , after 

correcting 2 σˆ for small sample sizes by using σ2 = q 2 σˆ /df, with 

df = degree of freedom, being 1 for the exponential and 2 for 

the logistic model (Dennis and others, 1991).

The process variability, estimated by σ2, represents 

both environmental stochasticity, σ2

env , and variance due to 

sampling error, σ2

s-error. Although sampling error does not 

significantly affect â, it produces a strong bias in σ2, which 

if not removed produces overly pessimistic PVAs (Morris 

and Doak, 2002). Accordingly, sampling error was removed 

from σ2 as follows: (1) the variance in Robs accounted for by 

sampling error was estimated as

1

2 2

1

var( ) var( ) var( ) , t t

t

t t

C C Robs

C C

+

+

= + (2)

where Ct is the mean population size estimated for year t; 

(2) the variance due to sampling error, after correcting for 

small samples, was estimated as the average variance of all 

var(Robst) obtained before; and (3) the environmental variance 

was then estimated as σ2

env = σ2tot – σ2s–error , with σ2tot = σ2

 , 

estimated during model fitting (Morris and Doak, 2002, p. 

163).

Variance of population estimates, var(Ct), was estimated 

from a log-normal distribution, Ct • eεZt , with εZt being 

normally distributed (Carpenter and others, 1994; Staples 

and others, 2004). This distribution has the property that the 

standard deviation ε equals the coefficient of variation (CV) 

of the census data (Carpenter and others, 1994) . Finally, 

var(Ct

) was estimated from 2,000 bootstraps of Ct • eεZt . 

The CV values used were estimated as follows: (1) a CV of 

approximately 1 percent (ε = 0.01) was included for direct 

nest censuses conducted at Midway Atoll, French Frigate 
78 Status Assessment of Laysan and Black-Footed Albatrosses, North Pacific Ocean, 1923–2005

Shoals, and Laysan Island (only black-footed albatrosses 

since 1998), as derived from field studies conducted at 

Midway Atoll (Flint, 2005), and (2) the USFWS provided 

population estimates and 95-percent confidence intervals 

derived from the assumption of normality in the distribution 

of nests per quadrant (1 quadrant = 100 m × 5 m strip transect) 

for population estimations derived from transect samples 

conducted at Laysan Island for both species since 1992. In 

both species, but particularly for black-footed albatross, there 

were a high proportion of quadrants having no black-footed 

albatross nests, thus causing the sampling distribution to 

significantly depart from normal. Data exploration indicated 

that a negative binomial (NegBin) distribution fit the data 

better than other models tested (that is BFAL 2003: lognormal: 

SSE=0.331; Poisson: SSE=0.038; NegBin: SSE=0.002). 

Accordingly, the mean number of nests per quadrant and its 

confidence interval were estimated for each species using 

the NegBin distribution and the likelihood profile of the 

mean (Hilborn and Mangel, 1997). Total population 

estimates were obtained by multiplying these estimates by 

the number of quadrants on the island. The CV was estimated 

from the estimated standard error (SE) of the mean, as 

(mean - 2.5%CI)/1.96, and divided by the mean estimated, 

CV~SE/mean.

Including sampling error when estimating parameters 

improves both model selection and parameter estimation 

(Carpenter and others, 1994). Sampling error was included by 

fittingeq. 1 to 3,000 generated data sets, each one created by 

adding sampling error to the actual census data series by using 

Ct • eεZt. The distribution of each parameter was then described 

by the median, 2.5 and 97.5 percent sampling percentiles of 

the 3,000 L(âi*, ˆ

i b *, 2 ˆσ i *) so obtained, and sampling variance 

was removed from the total variance estimated as indicated 

above.

Model selection was conducted using the corrected 

Akaike Information Criterion, 

2 2

1

pq AICc MLE

q p

= − + − −

, (3)

with maximum log-likelihood estimate (MLE, Morris and 

Doak, 2002). Differences between the exponential and 

logistic model were analyzed using the LR test proposed by 

Dennis and Taper (1994). LR = logL(ø1)/logL(ø2), where 1 

is the exponential and 2 is the logistic model, was estimated 

and compared with an empiric distribution of LR obtained 

from adjusting both models to 5,000 generated datasets from 

the original exponential model’s parameters, L(â, 2 σˆ ), and 

obtaining LRi, where i = 1, 2, ...5,000. The null hypothesis, 

H0: exponential model, is rejected if the original LR is greater 

than the 95 percent sampling percentile of LRi

.

Population forecasting was conducted using the 

exponential model. Although the logistic model fit the Robs

data better for some islands and species, it tended to overcompensate for population declines (Morris and Doak, 2002). 

The exponential model is a better representation of the current 

trend of the breeding population and as such, provides a 

better evaluation of the potential effect of present threats. A 

weakness of the exponential model is that it provides no clues 

about the factors underlying the population trend and can be 

strongly affected by environmental stochasticity.

Population trends were estimated for the 60 years 

following the last census data available, and the rate of 

population change was calculated as the difference between 

the final (Nf

) and initial (Ni) population sizes divided by 

the initial population size, ΔN = (Nf – Ni )/Ni . To facilitate 

comparisons of population trends between species, and 

with the Lewison and Crowder (2003) analysis, population 

projections were conducted for both species over 60 

years. This time interval met IUCN guidelines of using 

three generations, which for these species varies between 

18–28 years (International Union for Conservation of Nature 

and Natural Resources, 2004), while also keeping the time 

horizon low, thus reducing the multiplying effects of 

parameter error and process uncertainty (Morris and Doak, 

2002). Projection of the errors of parameter estimation 

was accomplished with parametric bootstrapping (Dennis 

and Otten, 2000). Using the parameters estimated with the 

exponential model, â and σ2

env , 1,000 data sets of the same 

length and starting population size as the original data were 

generated using eq. 1. For each simulated dataset, the MLEs of 

a and σ2 were found and denoted L(âi*, 2 ˆσ i *), where 

i = 1, 2,...1,000. Each i set of parameters was then used to 

generate 1,000 projections 60 years into the future. For each 

j

th projection (j = 1, 2,...1,000) with the ith set of parameters, 

the rate of change ΔNj,i was computed and the median rate of 

change ΔN

i , plus characteristic sampling percentiles, were 

estimated. Together, these 1,000 ΔN

i

 estimates constitute 

an estimate of the sampling distribution of ΔN , from which 

adequate descriptors, such as the 2.5 and 97.5 percent 

percentiles can be readily calculated. In both models, if the 

population size declined to a single individual, the population 

was considered extinct.

Age Structured Population Modeling

Historical Breeding Population Trajectory

Predictions of the historical size of breeding populations 

were determined by fitting a logistic curve to point estimates 

of the breeding population on each island where Laysan and 

black-footed albatrosses nest (figs. 6 and 14). The blackfooted albatross population estimate of Fisher and Baldwin 

(1946) was the sum of the chicks and their parents, which 

we divided by three to determine the number of breeding 

pairs. Population surveys described in the above studies 

were carried out during different phases of the breeding 

cycle, so we estimated the number of pairs laying eggs based 

on mean demographic parameters for Laysan and blackfooted albatrosses, respectively, estimated using data from 

Midway Atoll from 1992 to 2001 (U.S. Fish and Wildlife 
Appendix C 79

Service, unpub. data, 2005): hatching success = 0.804 and 

0.69 and breeding success = 0.495 and 0.55. In all cases, 

except recently colonized islands (Japan and Mexico), the 

logistic model was a better fit to the data than the exponential 

model. In each case the residuals’ standard deviation was 

estimated and added to obtain an interval for the expected past 

population size. The world population size was then estimated 

by summing up the mean ± 1 SD estimates from each island. 

Additional information obtained was an estimation of the 

nesting carrying capacity for each island and for the whole 

species.

Model Structure

The population trajectory estimated above was 

modeled using an age-structured, deterministic matrix model 

implemented in R-software. The basic model includes 10 age 

classes, with eggs in age 0, juveniles from age 1 to 7, and 

adults from age 8 and above. Individuals were considered 

to start breeding at age 8 (as in Cousins and Cooper, 2000). 

Reproduction was considered to occur in one pulse on 1 

January, which corresponds closely to breeding censuses dates 

conducted by the USFWS. Breeding frequency and breeding 

success were kept constant. Juveniles of age 1 were estimated 

as the number of eggs laid multiplied by breeding success and 

fledgling survival rate, S1.

A density-dependent version of the model was also 

implemented. Under natural conditions, survival rate probably 

decreases as per capita food availability decreases. Here we 

considered a contest model of competition, with all individuals 

having the same chance of obtaining food. Accordingly, 

survival of fledglings, juveniles, and adults were modeled 

using a single function as follows (Caswell, 1997): S • e–b·Nt

 , 

with S = survival rate value when Nt~0, Nt = total population 

size, b = constant that measures the strength of the densitydependence.

Parameter Estimation

Parameter values were estimated by fitting a random 

combination of values to the expected breeding population 

trend that included fishery bycatch. There is great uncertainty 

in demographic parameter values, mostly due to inconsistent 

and fragmented banding and recovery efforts (see Cousins 

and Cooper, 2000; Lewison and Crowder, 2003), and the 

non-independence of these estimates with fishery bycatch 

levels. The pelagic fishery started in 1952 (fig. A7), which is 

before the earliest banding program. Consequently, all survival 

estimates may be affected by fishery mortality. This factor 

had not been identified in previous assessments and may 

significantly influence results. To avoid this problem, we had 

the model choose the parameter value after adding different 

levels of fishery bycatch (see below). Parameter values were 

not correlated. Finally, the chosen set of parameters in each 

iteration was saved only if the model outcome from 1923 to 

2005 satisfied the following requirements:

1. The breeding population size estimated for 2005 must 

be within N2005•e(±0.05*1.96) corresponding to the breeding 

population size estimated for 2005 and a 95-percent CI 

assuming a log-normal error distribution with a CV = 5 

percent, which is about the CV for USFWS censuses.

2. The breeding population size projections for all years 

must be within ± 1 SD of the historical population size 

estimate.

Initial parameter values for each projection were selected 

at random from uniform distributions containing the most 

plausible range of natural values for each parameter (table 10). 

The ranges used for each parameter were:

• Breeding frequency, BF={0.65, 0.66,..., 0.85}

• Breeding success, BS={0.50, 0.51,..., 0.70}

• Survival of fledglings, S1={0.70, 0.71,..., 0.90}

• Survival of juveniles, Sjuv={0.930, 0.935,..., 0.990}

• Survival of adults, Sad={0.940, 0.945,..., 0.990}

• Density-dependent parameter: for the Laysan albatross, 

b={1•10-9, 2•10-9,...,1•10-6}, estimated after several 

runs; for the black-footed albatross, b={1•10-13, 

2•10-13,...,1•10-9}; estimated after several runs.

 Using values from these parameter ranges, 100 

parameter combinations were obtained for each fishery 

bycatch scenario. Confidence intervals for each parameter, 

without the effect of fishing mortality, were obtained. Finally, 

the maximum growth rate of the population, λmax, was 

calculated using the dominant eigenvalue of the populationprojection matrix (Caswell 1997), with the function Schur of 

the Matrix package for R (Bates and Maechler, 2005).

Fishery Bycatch Impact

Fishery bycatch levels used are those presented in 

section, “Threats” and summarized in figures 3 and 4. These 

estimates represent two mortality hypotheses regarding the 

bycatch rate used to estimate the total International pelagic 

longline fleet mortality (table A8). For the Laysan albatross, 

Hypothesis 1 (H1) uses a lower estimate, ca. 0.027 birds per 

1,000 hooks and Hypothesis 2 (H2) uses a higher estimate, ca. 

0.187 birds per 1,000 hooks. For the black-footed albatross, 

H1 = 0.073 birds per 1,000 hooks and H2 = 0.208 birds per 

1,000 hooks (appendix A). Results include estimates of adult 

and juvenile survival and the observed population growth rate 

(λ) after adding fishing mortality.
80 Status Assessment of Laysan and Black-Footed Albatrosses, North Pacific Ocean, 1923–2005

The effect of current fishery bycatch on the population 

trend was evaluated by incorporating different bycatch 

scenarios into the modeling process and by estimating the 

Potential Biological Removal (PBR) level for the species 

(Wade, 1998).

Fishery mortality was included in the matrix model by 

removing juvenile and adult individuals from the population 

between censuses, thus affecting only juvenile and adult 

survival rates. The number of individuals killed was extracted 

in a single event, just before reproduction (or census). The 

individuals killed were discounted from the population, 

assuming that juveniles and adults have the same chance of 

getting caught, thus mortality depends only on the relative 

abundance of each age-class. The world population was 

modeled as a whole; therefore albatrosses from all islands had 

the same probability of being killed by fishing operations. 

Accordingly, the number of albatrosses of each age-class 

killed by fisheries, or surviving to the next year, was estimated 

as:

, 1 , , ( ) ,

where

is defined as {1,..., 8, +8}

N N F S a t a t a t a

a

+ = −  (4)

,

,

,

,

,

 ,

where 

is defined as number of individuals in the ageclass during year , 

is defined as number of individuals in the ageclass killed by fisheries during year , 

a t

a t t

y t

a t

a t

N

F F

N

N a

t

F a

t

= 

,

is defined as yearly survival rate of age-class , and

is defined as total number of juveniles and adults 

(age-classes 1 to +8) in year .

a

y t

S a

N

t

(5)

In addition, albatross mortality at Midway Atoll due to 

‘control programs’ (see table 2) was considered to affect only 

breeding albatrosses and was subtracted from age-class +8 at 

the same time as those dying as a result of bycatch.

The impact of fishery bycatch on population viability was 

determined by estimating the PBR level. PBR depends on the 

maximum population growth rate (λmax ; there is no humaninduced mortality), the population size, a density-dependent 

factor, and a ‘recovery factor’ (Wade, 1998). For this analysis 

we used a density-dependent factor of 0.5 (Wade, 1998) and 

a recovery factor of 0.5, following the U.S. Marine Mammal 

Protection Act guideline when the actual population size is 

used (Caswell and others, 1998). The PBR was then estimated 

as R= (λmax–1)•0.5•0.5 (the density-dependent and correction 

factors). The impact that fishery bycatch had on the population 

was estimated in two ways: (1) as a rate, using R and F/Nt and 

(2) the absolute number of albatrosses removed, R•Nt and F

(where F = number of albatrosses killed by fisheries, 

Nt = total number of albatrosses). The mortality rate due to 

military activities was estimated in the same way.

Additionally, for the black-footed albatross, we evaluated 

the probability that a given fishery bycatch scenario would 

exceed the PBR estimation as follows (after Caswell and 

others, 1998):

P(0.5•0.5•Ri – Mj)≤0, probability that the fishery 

mortality rate Mj exceeds Ri,

Ri = (λi – 1), maximum population increase rate using λi,

Mj = Fj/Nti, fishery mortality, as the quotient between

Fj, the total number of birds killed by fisheries under the 

scenario j, and Nti, the population size in year t = 2005 using 

the λi population estimate.

The probability of exceeding Ri was estimated using λi

and Nti, with i = 1,..., 100 (estimated previously, see section, 

“Parameter Estimation”), against increasing fishery bycatch 

levels for 2005. For this analysis, the population size Nt was 

estimated as the sum of juveniles and adults (age-classes 1 to 

+8) for the estimated population size in 2005.
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For more information concerning the research in this report, contact the

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160 Holdsworth Way

University of Massachusetts Amherst

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Arata and others—Status Assessment of Laysan and Black-Footed Albatrosses, North Pacific Ocean, 1923–2005—Scientific Investigations Report 2009-5131