ACCESS NUMBER: 30670

STUDY TITLE: Barren Islands Seabirds

REPORT TITLE: Annual Variation in Seabird Attendance and Productivity on East Amatuli

Island, Barren Islands, Alaska: Natural and Human-Induced Effects.

CONTRACT NUMBER: COOPERATIVE AGREEMENT MMS 14-35-0001-30670

SPONSORING OCS REGION: Alaska

APPLICABLE PLANNING AREA (S): Cook Inlet; Gulf of Alaska

FISCAL YEAR(S) OF PROJECT FUNDING: 1992-1994

COMPLETION DATE OF REPORT: March 1996

COSTS: FY 1992: $98,750; FY 1993: $127,008; FY 1994: $ 10,000; CUMULATIVE PROJECT

COST: $235,758

PROJECT MANAGER: J. Parrish

AFFTh1ATION:Zology Department, University of Washington

ADDRESS: Box 351800; Seattle, Washington 98195

PRINCIPAL INVISTIGATOR: P. D. Boersma

KEYWORDS: A1ska; Gulf of Alaska; Barren Islands; East Amatuli Island; Fork-tailed

Storm-petrel; Oce2znodromafurcata; Common Murre; Uria aalge; Exxon Valdez; phenology;

reproductive success; population size; growth; food limitation; seabird; productivity; attendance;

effects.

BACKGROUND Anticipated oil and gas lease sales in Lower Cook Inlet and the Exxon Valdez

oil spill of 1989 pompted the U. S. Department of the hterior to continue a monitoring program

of the health of seAbirds nesting in the Barren Islands, the largest seabird colony in the North

Gulf of Alaska, and the largest colony in the path of the Exxon Valdez oil spill.

OBJECTIVES: (1) Monitor annual population and breeding parameters for Fork-tailed Stormpetrels and Comnon Murres nesting on East Amatuli Island; (2) Determine whether these

species were increasing, decreasing, or stable in both population size and breeding success

relative to the 1970's, 1980's, and early 1990's.

DESCRIPTION: The Barren Islands, (58° 55' N, 152° W), bave the largest seabird breeding

colonies in the North Gulf of Alaska. Because seabirds often are abundant, conspicuous, and
relatively high on the food chain, changs in population dynamics can mirror changes in the -

ACCESS NUMBER: 30670

bio-physical environment, including food supplies, oceanographic events such as El.

Nino-Southern Oscllation (ENSO), and marine pollution such as oil spills. From 1990 through

1994, we monitored the population activity, phenology, and reproductive success of the Common

Murre (Uria aalke) and Fork-tailed Storm-petrel (Oceanodromafurcata) in the Barren Islands,

Alaska, in order to determine the degree to which each species responded to natural and

human-induced changes in the environment. Fork-tailed Storm-petrel chick growth also was

monitored. For th most part, methods and censusing sites were based on OSCEAP studies

conducted by Boerèma and Manuwal during the late 1970's and early 1980's: In most years field

studies extended form early July to early September.

For Common Murres, patterns of population activity were estimated by counting murres

present on four separate nesting areas (approximately 2- 3% of total island attendance), after the

murres had laid egs but before chicks had fledged. Phenology was assessed from the timing of

egg production on A 5x5m study plot on the top of Light Rock, established in 1977, as well as

35mm time-lapse movie camera plots set up in 1991, 1993, and 1994. In addition, reproductive

succes was calculted for all pairs within the camera plots which could be visually followed.

For Fork-tailed Storm- petrels, patterns of population activity were estimated by assessing

occupancy, reproductive success, and chick growth at approximately 650 marked burrows

located in six study sites.

SIGNIFICANT CONCLUSIONS: Although there has been some concern that the Exxon

Valdez oil spill caibed a persistent decline in the reproductive output of the remaining East

Amatuli Common murre population, we found no evidence to support or refute this contention.

However, the pre-spill data required for accurate comparison was lacking, greatly weakening any

conclusions about the effects of the spill. Fork-tailed Storm-petrels appeared to be unaffected by

the spill; however, population parameters of this species varied widely over the study period.

The dramatic diffe ences in Fork-tailed Storm-petrel annual chick growth may reflect fledging

success to some degree, but also reflects the fact that storm-petrel growth is regulated by food

supply. Changes i41 weight gain probably reflect food quantity, while changes in wingchord

growth rate reflOctchangesin food quality. Food availability may change on an intraseasonal

basis and in an unredictable fashion, while food quality may be changing over longer periods of

time (e.g. decades).

STUDY RESUL 5: From 1975 through 1979, murre attendance estimates on East Amatuli

Island ranged from a low of 19,000 to a high of 61,000. From 1990 to 1992, we counted between

31,000 and 35,000 murres in attendance on East Amatuli Island. Attendance in three of the four

census areas increased steadily from 1990 to 1993; in total, attendance rose an

estimated 18% anAually. In all years, murres nesting on Light Rock produced eggs and chicks,

although there weie differences in both phenology and reproductive success. Egg laying on the

5x5m plot in 1977 and 1978 was early relative to 1979; the former years are phenologically

comparable to 1993 and 1994, while 1979 is closer to the timing of 1990. Reproductive
success of the 243 pairs of murres followed in the time-lapse camera plots ranged from 0.65 to

0.93 fledglings per pair.

ACCESS NUMBER: 30670

Throughout the 1990's, Fork-tailed Storm-petrel occupancy in marked nests hovered

between 40 and 50 percent. Hatching success and fledging success appeared to rise throughout

the 1990's to a high of nearly 70% (hatching) and 90% (fledging) in 1994. Both tissue growth

rate and weight gain fluctuated throughout the 1990's. In 1993 and 1994, it took approximately

57 days for the average chick to grow their wings from 10% (birth) to 90% of adult wingchord

length. By contras , the average length of time required in 1990 was 68 days, an approximately

20% difference. Weight gain followed a similar pattern.

STUDY PRODU TS: P. D. Boersma, and J. K. Parrish. 1996. Annual Variation in Seabird

Attendance and Produtivity on East Amatuli Island, Barren Islands, Alaska: Natural and

Human-Induced Eltfects. Final Report 1992- 1994. OCS Study MMS 96-0005,42 p.

P. D. Boersma, J. 1. Parrish, and A. B. Kettle. 1995. Common Murre abundance, phenology,

and productivity on the Barren Isalnds, Alaska: The Exxon Valdez oil spill and long-term

environmental chakge. In: Exxon Valdez Oil Spill: Fate and Effects in Alaskan Waters, ASTM

STP 1219. PG. \\e1ls, J. N. Butler, & J. S. Hughes, (Eds.). American Society for

Testing and Materials, Philadelphila.

J. K. Parrish, and P. D. Boersma. 1995. Muddy waters. American Scientist 83:112-115.
55' a.500 I I I 0' I65° 60° 55° ) ISO' / 45° 1 a' % 140° .1 SH U MA GIN COOK INLET a/ A L A S KA KODIAK KODIAK 'ANCH0AOI. L GULF OF ALASKA SUBREGION 163° iso° . tsS° 130° 143° I I I I GULF OF ALASKA 'I. JUHIAU 50° - STATUTI MILlS 0 50 lOG ISO IIILO*.IYlfl 0 so IOU ISO IO ISO 140 1306t- 135° CANADA
East Amatuli Islan4 Barren Islands, Abska Figure 1. Topographic map of East Amatuli Island, Barren Islands, Alaska, showing the placement of six Fork-tailed Storm-petrelstudy areas with permanently marked burrows (A, B, C, D, E, Z), the Common Murre census areas(Oval, Swatch, Triangle Rock), and Light Rock - the site of Common Murre reproductive success assessment (5x5m plot; 35mm time-lapse camera plots). Inset is location of East Amatuli relative to the Barren Islands system. .s nit