Status Review 

and Conservation 

Recommendations 

for the Gull-billed Tern 

(Gelochelidon nilotica) 

in North America

Biological Technical Publication

BTP-R1013-2010

U.S. Fish & Wildlife Service

Larry Ditto©

i

Kathy C. Molina1

R. Michael Erwin2

Eduardo Palacios3

Eric Mellink4

Nanette W. H. Seto5, 6

1 Natural History Museum of Los Angeles County, Los Angeles, CA

2 U.S. Geological Survey, Patuxent Wildlife Research Center, 

University of Virginia, Charlottesville, VA

3 Centro de Investigación Científica y de Educación Superior de Ensenada 

(CICESE Unidad La Paz), Pronatura Noroeste, A.C., La Paz, B.C.S. México

4 Centro de Investigación Científica y de Educación Superior de Ensenada 

(CICESE), Ensenada, B.C., México

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

Portland, OR

6 Current Address: Migratory Bird Management, Arlington, VA

Status Review 

and Conservation 

Recommendations 

for the Gull-billed Tern 

(Gelochelidon nilotica) 

in North America

Biological Technical Publication

BTP-R1013-2010

U.S. Fish & Wildlife Service

Cover image: Gull-billed Tern

Photo credit: Larry Ditto©
ii Status Review and Conservation Recommendations for the Gull-billed Tern

For additional copies or information, contact:

U.S. Fish and Wildlife Service

Pacific Southwest Region, Migratory Birds Program

2800 Cottage Way

Sacramento, CA 95825

Recommended citation:

Molina, K. C., R. M. Erwin, E. Palacios, E. Mellink, 

and N. W. H. Seto. 2010. Status review and 

conservation recommendations for the Gull-billed 

Tern (Gelochelidon nilotica) in North America. 

U.S. Department of Interior, Fish and Wildlife 

Service, Biological Technical Publication, FWS/

BTP-R1013-2010, Washington, D.C.

Series Senior Technical Editor:

Stephanie L. Jones

U.S. Fish and Wildlife Service, Region 6

Nongame Migratory Bird Coordinator

P.O. Box 25486

Denver Federal Center

Denver, Colorado 80225-0486

Author contact information:

Kathy C. Molina

Natural History Museum of Los Angeles County

Section of Ornithology

900 Exposition Blvd.

Los Angeles, CA 90007

Phone: (213) 763-3368

E-mail: kmolina@nhm.org

R. Michael Erwin

U.S. Geological Survey

Patuxent Wildlife Research Center

Department of Environmental Sciences

University of Virginia

291 McCormick Rd.

Charlottesville, VA 22904

Phone: (434) 924-3207

E-mail: rme5g@virginia.edu

Eduardo Palacios

Centro de Investigación Científica y de Educación 

Superior de Ensenada

(CICESE Unidad La Paz)

Pronatura Noroeste

A.C., Miraflores 334 e/ Mulegé y La Paz. Fracc. 

Bella Vista

La Paz, B.C.S. 23050

México

Phone: (612) 121-3031, Ext. 111

E-mail: epalacio@cicese.mx

Eric Mellink

Centro de Investigación Científica y de Educación 

Superior de Ensenada

(CICESE)

Km 107 Carr. Tijuana-Ensenada

Ensenada, B.C.

México

U.S. Mailing Address:

P. O. Box 434844

San Diego, CA 92143-4844

Phone: (646) 175-0500

E-mail: emellink@cicese.mx

Nanette W. H. Seto (Current Address):

U.S. Fish and Wildlife Service

Migratory Bird Management

4401 N Fairfax Drive, MBSP 4107

Arlington, VA 22203

Phone: (703) 358-1835

E-mail: nanette_seto@fws.gov
Table of Contents iii

Table of Contents

List of Figures v

List of Tables vi

Executive Summary viii

Acknowledgments ix

Taxonomy 1

Legal Status 2

United States 2

Mexico 2

Central America and West Indies 2

Description 3

Geographic Distribution 4

Breeding 4

Gelochelidon nilotica aranea 4

Gelochelidon nilotica vanrossemi 4

Subspecies undetermined 4

Wintering 4

Gelochelidon nilotica aranea 4

Gelochelidon nilotica vanrossemi 5

Subspecies undetermined 5

Migration and Vagrancy 5

Gelochelidon nilotica aranea 5

Gelochelidon nilotica vanrossemi 5

Summer Non-breeding 5

Natural History 6

Breeding 6

Colonies, nests, and nest spacing 6

Reproductive phenology 6

Breeding site fidelity 6

Demography and limiting factors 6

Predators 7

Diet 7

Foraging Behavior 7

Post-breeding Dispersal 7

Population Estimates and Trends 8

Estimates 8

Gelochelidon nilotica aranea 8

Gelochelidon nilotica vanrossemi 8

Trends 10

Gelochelidon nilotica aranea 10

Gelochelidon nilotica vanrossemi 10

Monitoring Activities 11

Breeding Bird Survey 11

Regional and State Surveys 11
iv Status Review and Conservation Recommendations for the Gull-billed Tern

Habitat Requirements 12

Breeding Season 12

Winter and Summer Non-breeding Seasons 12

Threats 13

Habitat Loss and Degradation 13

Overutilization 13

Disease and Predation 14

Inadequacy of Existing Regulatory Mechanisms 14

Other Natural or Manmade Factors 14

Storm events and other natural disturbances 14

Pesticides or other contaminants 14

Population size and colony distribution 15

Introduced species 15

Conflicts with other species 15

Other interspecific interactions 15

Other conflicts 16

Disturbance to nesting sites 16

Management and Conservation 17

Habitat Management 17

Predator Management 17

Artificial Nesting Habitat 18

Education 18

Conservation Recommendations 19

Monitoring 19

Habitat Management and Protection 19

Research 20

Conclusion 20

Literature Cited 21

Appendix A. State and Regional Summaries of Gelochelidon nilotica aranea Status within 

the Breeding Range in the U.S., Mexico, and Caribbean 26

United States 26

Alabama 26

Delaware and Maryland 27

Florida 28

Georgia 30

Louisiana 31

Mississippi 34

New Jersey and New York 35

North Carolina 38

South Carolina 42

Texas 45

Virginia 53

Caribbean 55

Mexico 56

Literature Cited, Appendix A 57

Appendix B. State Summaries of Gelochelidon nilotica vanrossemi Status within the 

Breeding Range in the U.S. and Mexico 61

Mexico

Baja California and Baja California Sur 61

Colima, Nayarit, Sinaloa, and Sonora 63

United States

California 65

Literature Cited, Appendix B 67

Appendix C. State and Regional Contacts and Contributors 69
List of Figures v

List of Figures

Figure 1. North American distribution of the Gull-billed Tern 1

Figure A-1. Locations and sizes of Gull-billed Tern colonies in Alabama, 2004 27

Figure A-2. Locations and sizes of Gull-billed Tern colonies in Florida, 2000 29

Figure A-3. Locations and sizes of Gull-billed Tern colonies in Georgia, 2003 30

Figure A-4. Locations and sizes of Gull-billed Tern colonies in Louisiana, 2001 33

Figure A-5. Locations and sizes of Gull-billed Tern colonies in Mississippi, 2003 33

Figure A-6. Locations and sizes of Gull-billed Tern colonies in New Jersey, 2001 37

Figure A-7. Locations and sizes of Gull-billed Tern colonies in New York, 2003 37

Figure A-8. Locations and sizes of Gull-billed Tern colonies in North Carolina, 2001 38

Figure A-9. Locations and sizes of Gull-billed Tern colonies South Carolina, 2003 44

Figure A-10. Locations and sizes of Gull-billed Tern colonies in the upper coast of Texas, 2003 45

Figure A-11. Locations and sizes of Gull-billed Tern colonies in central coast of Texas, 2003 48

Figure A-12. Locations and sizes of Gull-billed Tern colonies in the lower coast of Texas, 2003 51

Figure A-13. Locations and sizes of Gull-billed Tern colonies in Virginia, 2003 55

Figure B-1. Locations and sizes of Gull-billed Tern colonies in coastal northwest Mexico, 2003 62

Figure B-2. Locations and sizes of Gull-billed Tern colonies in coastal southwest Mexico, 2003 63

Figure B-3. Locations and sizes of Gull-billed Tern colonies in California, 2003 65
vi Status Review and Conservation Recommendations for the Gull-billed Tern

List of Tables

Table 1. State agency status of Gull-billed Terns in North America (continental United States only), 

and National Heritage Status (NatureServe Explorer 2006). “No status” indicates that the state 

has not it given the species a specific conservation status. 2

Table 2. Number of breeding pairs and colony sites of G. n. aranea in the continental 

United States for years in which comprehensive state-wide censuses were conducted. 9

Table 3. Number of breeding pairs and colony sites of G. n. vanrossemi in the Pacific Coast 

of the United States and Mexico in years surveys were conducted. 10

Table A-1. Number of Gull-billed Tern breeding pairs at colonies in Mobile County, Alabama, 

1988–2004 (R. B. Clay, pers. comm.). Dash (—) indicates data are insufficient to discern 

site availability, occupancy, or extent of survey coverage for a particular site and year. 26

Table A-2. Number of breeding pairs of Gull-billed Terns at colonies in Florida 1973–1977, 

1979, 1985, 1995, 1998–2000a. Dash (—) indicates data are insufficient to discern site availability, 

occupancy, or extent of survey coverage for a particular site and year. Data from Clapp et al. 

1983, Florida Fish and Wildlife Commission 2003, Loftin and Sutton 1979, Ogden 1974, 1975, 1979, 

Portnoy et al. 1981, Smith and Alvear 1997. 29

Table A-3. Numbers of breeding pairs of Gull-billed Terns in McIntosh County, Georgia 

1993, 1995, 1999 and 2003 (B. Winn, pers. comm.). 30

Table A-4. Number of breeding pairs of Gull-billed Terns at colonies along the coast of Louisiana, 

1976, 1990–1999 and 2001. Dash (—) indicates data are insufficient to discern site availability, 

occupancy, or extent of survey coverage for a particular site and year. Topographic quad names 

follow the Louisiana Natural Heritage Program (LNHP) colony identification numbers. 

Data from Martin and Lester 1990, Michot et al. 2004, Portnoy 1977, G. D. Lester, pers. comm. 32

Table A-5. Number of Gull-billed Tern breeding pairs at colonies in Jackson County, Mississippi, 

1988–2004 (M. P. Stevens, pers. comm.). Dash (—) indicates data are insufficient to discern 

site availability, occupancy, or extent of survey coverage for a particular site and year. 34

Table A-6. Number of breeding pairs of Gull-billed Terns at colonies in New Jersey, 1977, 1985, 

1995, and 2001 (Erwin and Korschgen 1979, R. Andrews and C. D. Jenkins, pers. comm.). 35

Table A-7. Number of breeding pairs of Gull-billed Terns at colonies in New York, 1975, 1984–1999, 

and 2001–2003. Dash (—) indicates data are insufficient to discern site availability, occupancy, 

or extent of survey coverage for a particular site and year. Data from Buckley et al. 1975, 

Sommers et al. 1994, 2001, M. R. Wasilco, pers. comm. 36
List of Tables vii

Table A-8. Number of breeding pairs of Gull-billed Terns at colonies in North Carolina, 1976–1977, 

1983–1993, 1995, 1997, 1999, and 2001. Surveys conducted statewide in 1976, 1977, 1985, and 1993 

through 2001 were comprehensive. Dash (—) indicates data are insufficient to discern site availability, 

occupancy, or extent of survey coverage for a particular site and year. Data from Parnell 

and Soots 1979, Parnell et al. 1995, Portnoy et al. 1981, D. H. Allen, pers. comm. 39

Table A-9. Number of breeding pairs of Gull-billed Terns at colonies in South Carolina, 1975–1976, 

1979, 1986–1990, and 1992–2003 (Portnoy et al. 1981, T. M. Murphy, pers. comm.). Statewide 

census effort begins about 1987; earliest censuses may not have been comprehensive. 

Dash (—) indicates data are insufficient to discern site availability, occupancy, or extent of 

survey coverage for a particular site and year. 43

Table A-10. Number of breeding pairs of Gull-billed Terns at colonies along the upper coast of Texas, 

1988–2003 (U.S. Fish and Wildlife Service 2004). Dash (—) indicates data are insufficient to discern site 

availability, occupancy, or extent of survey coverage for a particular site and year. 46

Table A-11. Number of breeding pairs of Gull-billed Terns at colonies along the central coast 

of Texas, 1988–2003 (U.S. Fish and Wildlife Service 2004). Dash (—) indicates data are insufficient 

to discern site availability, occupancy, or extent of survey coverage for a particular site and year. 49

Table A-12. Number of breeding pairs of Gull-billed Terns at colonies along the lower 

coast of Texas, 1988–2003 (U.S. Fish and Wildlife Service 2004, D. S. Stolley, pers. comm.). 

Dash (—) indicates data are insufficient to discern site availability, occupancy, or extent of 

survey coverage for a particular site and year. 52

Table A-13. Number of breeding pairs of Gull-billed Terns at colonies in Virginia, 1975–1977, 1984, and 

1993–2003 (Williams et al. 1990, R. Andrews, B. R. Truitt and B. D. Watts, pers. comm.). Comprehensive 

surveys conducted statewide in 1977, 1984, 1998, and 2003. 54

Table B-1. Number of breeding pairs of Gull-billed Terns at colonies in Baja California and 

Baja California Sur, México, 1992–1994, 1996–2005. Dash (—) indicates no survey was 

conducted; n/a = birds were present but not counted. Data from Danemann and Carmona 2000, 

Molina and Garrett 2001, Palacios and Mellink 1993, 2007, EM, KCM, EP. 61

Table B-2. Number of breeding pairs of Gull-billed Terns at colonies in western Mexico 

(Sinaloa through Colima), 2000–2005. Dash (—) indicates no survey was conducted. 

Data from Palacios and Mellink 2007, X. Vega and M. A. Gonzalez, pers. comm., EM, EP. 64

Table B-3. Number of breeding pairs of Gull-billed Terns at colonies in California, 1992–2006 

(Molina 2004, R. T. Patton, pers. comm., KCM). 66
viii Status Review and Conservation Recommendations for the Gull-billed Tern

Executive Summary

The Gull-billed Tern (Gelochelidon nilotica) is a 

medium-sized tern that breeds in small, scattered, 

often ephemeral colonies, typically in habitat 

devoid of vegetation near marine waters or saline 

lakes. In North America, the species breeds along 

the Atlantic coast south of New York, the Gulf of 

Mexico, and the Pacific coast of California and 

Mexico. Its distribution has contracted from known 

historic range along the Atlantic Coast, but has 

expanded along the Pacific Coast. Range changes in 

Mexico are unknown due to fragmentary knowledge 

of historical colony locations, but some range 

contraction may have occurred. Two subspecies 

(G. n. aranea and G. n. vanrossemi) occur in 

North America. The current population of 

G. n. aranea in the United States is estimated to be 

approximately 3610 pairs, over 60% of which occur 

in Texas. The number of birds in Texas appears 

stable, but the number of individuals has declined 

in Maryland, Delaware, Virginia, North Carolina, 

Florida, and possibly Georgia. G. n. vanrossemi has 

737 to 808 pairs breeding in western Mexico and 

southern California.

Gull-billed Terns are designated as a Bird of 

Conservation Concern by the U.S. Fish and Wildlife 

Service. G. n. aranea is designated as endangered, 

threatened or of management concern in nine 

states and G. n. vanrossemi is designated as a Bird 

Species of Special Concern in California.

The main causes of population declines in North 

America are disturbance of nesting colonies, 

loss of natural nesting islands, and development 

or modification of upland foraging habitats. 

This species often nests on artificially deposited 

substrates, suggesting it could respond to 

management of breeding habitat.

Management priorities for Gull-billed Terns 

are: (1) protection of known nesting colony sites; 

(2) enhancement and conservation of potential 

nesting and foraging areas; (3) predator control; 

(4) development of population viability models; and 

(5) resolution of conflicts with other species and 

aquaculture. Research and monitoring needs are: 

(1) resolution of the subspecific identity of birds 

breeding in North America; (2) demographic studies 

addressing population viability; (3) the identification 

and linkage of breeding and non-breeding ranges; 

(4) studies of habitat use and ecology during the 

breeding and non-breeding seasons, especially 

in Mexico and Central America; (5) continued 

monitoring of breeding colonies, particularly in the 

Gulf Coast of Mexico; and (6) the establishment of 

monitoring efforts in the West Indies.
Acknowledgements ix

W. McFarlane, David J. Newstead, Robert D. 

Purrington, Mary P. Stevens, Dorie S. Stolley and 

Jennifer K. Wilson for responding to numerous 

requests and providing additional information. 

We are particularly grateful for the help provided 

by Roger B. Clay, Philip Glass, Paul L. Leberg, 

Thomas C. Michot, and William J. Vermillion. We 

thank Michael T. Green and Tara S. Zimmerman 

for their support, guidance and editorial advice. 

We thank Geoff Sanders for assistance in data 

compilation. We thank Elizabeth Cruz, National 

Wildlife Refuge System, Pacific Region, Portland, 

Oregon for assistance in development of figures. We 

thank David Blankinship, Jenny Hoskins, William 

H. Howe, William J. Vermillion, and a number of 

anonymous reviewers for their helpful suggestions 

on earlier drafts and particularly Kimball L. 

Garrett for many insightful discussions, help with 

literature references and suggestions on an earlier 

draft of the manuscript. We thank Patricia Worthing 

for her editorial assistance. Funding for this status 

assessment was provided by the U.S. Fish and 

Wildlife Service, Regions 1, 2, 4, 6, and 8 nongame 

migratory bird programs.

We thank the following colonial waterbird survey 

coordinators, database managers, breeding bird 

atlas managers and researchers for graciously 

providing unpublished information: David H. Allen 

(North Carolina), David F. Brinker (Maryland), 

J. Steve Calver (Georgia), Susan E. Cameron 

(North Carolina), Roger B. Clay (Alabama), Brian 

E. Collins (California), Michelle L. Gibbons (New 

York), Philip Glass (Texas), Joe A. Halbrook 

(Texas), Howard Horne (Alabama), C. David 

Jenkins (New Jersey), Paul L. Leberg and Gary 

D. Lester (Louisiana), Tim Manolis (California), 

Robert W. McFarlane (Texas), Thomas C. Michot 

(Louisiana), Thomas M. Murphy (South Carolina), 

James F. Parnell (North Carolina), Robert T. Patton 

(California), Elisa Peresbarbosa (Mexico), Robert 

D. Purrington (Louisiana), James A. Rodgers 

(Florida), Martha Roman (Mexico), Henry “Hank” 

T. Smith (Florida), Todd Stefanic (California), 

Mary P. Stevens (Mississippi), Jenny Thompson 

(Mississippi), Barry R. Truitt (Virginia), Vincent 

V. Turner (New Jersey), Xicotencatl Vega Picos 

(Mexico), Michael R. Wasilco (New York), Bryan 

D. Watts and Bill Williams (Virginia), Jennifer K. 

Wilson (Texas), and Brad Winn (Georgia). We are 

grateful to Steven W. Cardiff, Mark A. Goodman, 

William H. Howe, Gregory D. Jackson, Robert 

Acknowledgments

Taxonomy 1

Class: Aves

Order: Charadriiformes

Family: Laridae

Scientific name: Gelochelidon nilotica Gmelin 1789

Common name: Gull-billed Tern

The Gull-billed Tern has a cosmopolitan but 

discontinuous distribution (Fig. 1) with six 

subspecies described based on variation in size 

and coloration of dorsal plumage. Two subspecies, 

Gelochelidon nilotica aranea and G. n. vanrossemi, 

occur in North America. The nominate subspecies 

G. n. nilotica breeds in small numbers in northern 

Germany and Denmark, and in scattered colonies 

across southern Europe south to northwestern 

Africa and east through Turkey and the Middle East 

Taxonomy

to Asia Minor, India and southern Mongolia (Cramp 

1985, Urban et al. 1986, Hagemeijer and Blair 

1997); it winters mainly in Africa and India. Poorly 

differentiated from nominate birds, the subspecies 

G. n. addenda (“G. n. affinis” of many authors is a 

synonym; Dickinson 2003) breeds in coastal China 

and perhaps elsewhere in eastern Asia, wintering 

south to southeast Asia and possibly northern 

Australia (Higgins and Davies 1996, Wells 1999). 

Australian breeding birds are the largest and palest 

subspecies, G. n. macrotarsa (Higgins and Davies 

1996). G. n. groenvoldi breeds locally in eastern 

South America from Brazil to northern Argentina 

(Blake 1977). The subspecific identity of breeding 

birds in southwestern Ecuador is unknown, though 

measurements are consistent with the subspecies 

G. n. aranea (Ridgely and Greenfield 2001).

Figure 1. North American distribution of the Gull-billed Tern.

Breeding only

Year-round (Breeding and wintering)
2 Status Review and Conservation Recommendations for the Gull-billed Tern

Legal Status

South Carolina, but has no specific conservation 

status in the remaining five states in its range 

(Appendices A and B). The National Heritage 

Status ranking for Gull-billed Terns is “Critically 

Imperiled” or “Imperiled” in 10 of the 14 states 

in its range (Table 1). The National Conservation 

status of Gull-billed Terns in the United States is 

“Apparently Secure” and its Global Heritage Status 

is “Secure” (NatureServe Explorer 2006).

Mexico

Gull-billed Terns are protected under the 1936 

Convention between the United States and Mexico 

for the Protection of Migratory Birds and Game 

Mammals, but have no special legal status in 

Mexico (Secretaría de Medio Ambiente y Recursos 

Naturales 2002).

Central America and West Indies

Gull-billed Terns appear to have no legal status in 

Central America or the West Indies.

United States

Gull-billed Terns are federally protected by the 

Migratory Bird Treaty Act (1918) (MBTA) in the 

United States (16 U.S.C. 703-712; Ch. 128; July 

13, 1918; 40 Stat. 755). The MBTA is the primary 

federal law that implements international treaties 

mandating the conservation and management of 

migratory birds jointly with Great Britain, Mexico, 

Japan, and Russia (16 U.S.C. 703-712, as amended). 

The species is listed by the U.S. Fish and Wildlife 

Service (USFWS) as a Bird of Conservation 

Concern at the national scale and in four USFWS 

Regions (Regions 2, 4, 5, and 8) and seven Bird 

Conservation Regions (BCRs 27, 30, 31, 32, 33, 36, 

and 37) (U.S. Fish and Wildlife Service 2008). These 

designations identify Gull-billed Terns as a species 

in need of conservation.

At the state level, Gull-billed Terns are listed 

as Endangered in Maryland and Threatened in 

Georgia, North Carolina, and Virginia (Table 1). 

It is a Species of Special Concern or equivalent in 

Alabama, California, Louisiana, Mississippi, and 

Table 1. State agency status of Gull-billed Terns in North America (continental United States only), and 

National Heritage Status (NatureServe Explorer 2006). “No status” indicates that the state has not it given 

the species a specific conservation status.

State Legal Status National Heritage Status

Alabama Protected Imperiled

California Species of special concern Critically imperiled

Delaware No status Possibly extirpated

Florida No status Imperiled

Georgia Threatened Critically imperiled

Louisiana Rare animal of conservation concern Imperiled 

Maryland Endangered Critically imperiled

Mississippi Species of greatest conservation need Imperiled 

New Jersey No status Critically imperiled

New York No status Critically imperiled

North Carolina Threatened Vulnerable

South Carolina Species of concern Unranked

Texas No status Apparently secure

Virginia Threatened Imperiled
Description 3

Gull-billed Terns are a medium-sized (35 cm, 

170–190 g) member of the Sterninae sub-family, 

best distinguished by the combination of its heavy 

black bill, black legs, and very pale gray upperparts. 

Compared to other medium-sized terns, it is longerlegged, has broader-based wings with longer outer 

primaries, and a shorter tail with a shallower fork. 

The following plumage information has been taken 

from Cramp (1985), Parnell et al. (1995), Sibley 

(2000), and from specimens at the University of 

California at Los Angeles Dickey Bird and Mammal 

Collection and the Natural History Museum of 

Los Angeles County.

Alternate-plumaged adults have a jet black crown, 

are white on the head and underparts, and very pale 

gray on the back, upperwings, rump, and tail. In 

basic plumage, adults lose the black cap and appear 

white-headed with a small dark gray patch behind 

the eye and indistinct black peppering on the crown. 

At fledging, juveniles show a buffy wash and interior 

brown markings on the back feathers and wing 

coverts, dark markings on the tertials and rectrices, 

and extensively dusky primaries. The crown of 

juveniles is whitish with fine dark spotting, and 

the patch behind the eye is gray. First alternate 

(one year old) birds resemble basic-plumaged adults 

but show some dark in the centers of the tertials 

and may show some black mottling on the center 

and rear of the crown. Second winter birds are 

essentially indistinguishable from basic-plumaged 

adults but differ subtly in molt limits and wear in 

the flight feathers. Second summer birds closely 

resemble alternate-plumaged adults but usually 

retain some white on the forehead.

The two North American subspecies (G. n. 

aranea and G. n. vanrossemi) are, on average, 

morphologically distinct, with G. n. vanrossemi

bigger overall. There is substantial overlap in most 

characteristics making it difficult to distinguish 

between the two subspecies (Parnell et al. 1995, 

Molina and Erwin 2006).

Description

Kathy Molina©
4 Status Review and Conservation Recommendations for the Gull-billed Tern

Geographic Distribution

Wintering

Gelochelidon nilotica aranea.—G. n. aranea

winters south of the central Atlantic coast of 

Florida, along the Gulf of Mexico coasts from 

Louisiana to the Lower Laguna Madre, in Texas, 

and possibly along the coasts of Tamaulipas and 

Veracruz in Mexico (Fig. 1). Howell and Webb (1995) 

suggest that the species occurs in winter along the 

entire Gulf of Mexico and Caribbean coastlines of 

Mexico, Belize (where uncommon; Jones 2003) 

and Honduras. Documentation indicates that a 

few birds winter in coastal Yucatan, Mexico 

(Gómez de Silva 2007).

Breeding

Gelochelidon nilotica aranea.—G. n. aranea

breeds along the Atlantic coast of the United States 

from Long Island, New York, south to northeastern 

Florida and locally in the interior of Florida 

(Fig. 1). Along the Gulf of Mexico coast, 

G. n. aranea breeds from Tampa Bay, Florida, 

west through coastal Alabama, Mississippi, and 

Louisiana to Texas and south to Tamaulipas 

(Garza-Torres and Navarro S. 2003) and possibly 

Veracruz, Mexico (Fig. 1; Parnell et al. 1995). 

Gull-billed Terns were absent along the eastern 

coast of Yucatan, Mexico in 1992 (Rangel-Salazar 

et al. 1993). Although their status and distribution 

in the Caribbean is poorly known, G. n. aranea is 

thought to breed sporadically and in small numbers 

on Caribbean islands from the Bahamas south 

to the British Virgin Islands and Anguilla 

(Chardine et al. 2000).

Gelochelidon nilotica vanrossemi.—In the western 

United States, G. n. vanrossemi breeds very locally 

in extreme southern California at San Diego Bay 

and at the Salton Sea (Fig. 1). In western Mexico, 

G. n. vanrossemi breeds in the Colorado River 

Delta in northeastern Baja California, as well as in 

coastal Sinaloa, Nayarit and Colima (Fig. 1; Palacios 

and Mellink 2007). G. n. vanrossemi has bred 

sparingly and infrequently at the Guerrero Negro 

saltworks in extreme northern Baja California Sur 

(Fig. 1; Danemann and Carmona 2000, Palacios and 

Mellink 2007).

Subspecies undetermined.—In Central America, 

Gull-billed Terns possibly breed in Panama (Ridgely 

and Gwynne 1989), but confirmed breeding records 

are lacking and the subspecific identity of possible 

breeders is unknown.

Matt Sadowski©
Geographic Distribution 5

from known breeding sites but normally occur 

within the general breeding range of the species. 

Small numbers may disperse northward as vagrants 

in spring, summer, and fall. Gull-billed Terns occur 

nearly annually in Massachusetts from May to 

September (Veit and Petersen 1993) and have been 

recorded in the Canadian Maritime Provinces 

in July and August (Godfrey 1986). Gull-billed 

Terns are casual or accidental in the interior of 

eastern North America (McWilliams and Brauning 

2000). Correa-Sandoval and Garcia-Barron (1993) 

considered the Gull-billed Tern to be a rare migrant 

in the large lagoon systems of Campeche and 

Yucatan, Mexico.

Gelochelidon nilotica vanrossemi.—G. n. 

vanrossemi migrates along the western coast of 

mainland Mexico and presumably the Pacific and 

Gulf of California coasts of the Baja Peninsula 

(Wilbur 1987, Erickson et al. 2001, 2004). Gull-billed 

Terns are casual or accidental in the interior of 

western North America (Monson and Phillips 1981), 

including interior southern California (Lehman 

1994, Hamilton and Willick 1996; McCaskie and 

Garrett 2001, 2004, 2005).

Summer Non-breeding

Small numbers of both subspecies over-summer 

within the respective portions of their winter 

ranges in Mexico (Howell and Webb 1995). 

Contreras-Balderas (1993) considered G. n. 

aranea as a year-round resident in Tamaulipas. 

In California, non-breeders (white-headed birds 

presumably in their second year) have been noted 

at breeding colonies at the Salton Sea (KCM).

Gelochelidon nilotica vanrossemi.—G. n. 

vanrossemi primarily winters in Mexico along the 

eastern Gulf of California from the Colorado River 

Delta south to Sinaloa and along the Pacific coast 

to Nayarit, Colima and Oaxaca (Howell and Webb 

1995). There are a few mid-winter records for the 

Salton Sea (Patten et al. 2003), the Mexicali Valley 

(R. A. Erickson, pers. comm.), and southern Baja 

California Sur (Fig. 1; Erickson et al. 2003).

Subspecies undetermined.—The non-breeding 

distribution of G. n. aranea and G. n. vanrossemi

from southern Mexico to northern South America 

is poorly understood. Gull-billed Terns winter in 

small numbers on both coasts of Honduras (Monroe 

1968), Costa Rica (Stiles and Skutch 1989) and 

Panama (Ridgely and Gwynne 1989). Although 

it is likely that migrant and wintering Gull-billed 

Terns on the Caribbean coast of Central and South 

America belong to the subspecies G. n. aranea,

the subspecific identity of birds wintering on the 

southern Pacific Coast is unclear (Molina and 

Erwin 2006). The single specimen from the Pacific 

coast of Honduras appears from measurements to 

be G. n. aranea (Monroe 1968), so some Gull-billed 

Terns on the Pacific coast of Central and South 

America may be of this subspecies. The pattern of 

eastern North American and Caribbean breeding 

populations wintering on the southern Pacific Coast 

occurs in other avian taxa (Molina and Erwin 2006).

Migration and Vagrancy

Gelochelidon nilotica aranea.—G. n. aranea

migrates through coastal areas of the Atlantic states 

and Gulf of Mexico. Migrants may be noted away 

Kathy Molina©
6 Status Review and Conservation Recommendations for the Gull-billed Tern

Natural History

Prieto, Mexico, although some years were 

not surveyed (Molina and Garrett 2001, KCM). 

Reasons for the difference in site-fidelity are 

unknown, but could be in response to the number 

of alternative sites or to management aimed at 

reducing disturbance and predation events in 

California (KCM).

Demography and limiting factors.—Few 

quantitative data are available on the demography 

of Gull-billed Tern populations in North America 

(Parnell et al. 1995). The average clutch size ranges 

from two to three eggs, with four eggs being 

exceptional (Bent 1921). In Virginia, from 1994 

through 1996, clutch size depended strongly on 

time of season; early clutches averaged 2.47 and 

late ones averaged 2.10 (n = 428; Eyler et al. 1999). 

In California, clutch size in 1993 averaged 2.2 (n = 

140; Parnell et al. 1995). The age of first breeding in 

Europe has been reported to be at least five years, 

with birds establishing non-nesting territories at 

four years of age (Moller 1975). At the Salton Sea, a 

few known-age birds have bred at three years and 

occasionally birds presumed to be two years of age 

loaf at colony sites (KCM).

Productivity estimates vary among years and 

locations, and lack of consistency in the variables 

measured often confound comparisons of 

reproductive success across studies. In Virginia 

from 1994 to 1996, Eyler et al. (1999) reported 

a mean brood size of 1.99 chicks, but only 

0.89 chicks per successfully hatched nest reached 

fledging age. For all nests initiated, including 

those lost to flooding or other causes, 0.53 chicks 

per nest survived to fledging age. In California, 

fledglings per pair in 2000 and 2001 for Salton Sea 

colonies were 0.57 and 0.31, respectively, and for 

the San Diego colony were 1.23 and 0.95, 

respectively (KCM).

Although Gull-billed Terns generally have only one 

brood in a breeding season, they may re-nest if the 

initial clutch or brood is lost (Parnell et al. 1995). 

No information on lifetime reproductive success is 

available; similarly, information on the longevity 

of Gull-billed Terns is scant. One bird banded as a 

chick in South Carolina was recovered in Guyana, 

South America when at least six years and four 

months old (Clapp et al. 1982). In Europe, the 

longevity record is 15 years, 10 months (Rydzewski 

1978). Several 10-year old birds, banded as chicks at 

the Salton Sea, have been observed in the vicinity of 

their natal colonies (KCM).

Breeding

Colonies, nests, and nest spacing.—Gull-billed Tern 

nesting colonies are generally small to medium in 

size (< 50 pairs) and are loosely aggregated (Parnell 

et al. 1995). In Texas, 90% of 136 colony sites in 

2003 contained a median of one to 50 pairs, eight 

sites (6%) contained 51 to 100 pairs, and six sites 

(4%) contained > 100 pairs. At the Salton Sea in 

California, Gull-billed Terns often form subcolonies 

of 10 to 30 pairs (KCM). Nests are small shallow 

scrapes typically containing little or no nest lining. 

Nest rims are composed of small bits of beach 

debris, (e.g. vegetation, small fish bones, bits 

of plastic, pebbles, and feathers). Both members 

of the pair participate in forming and maintaining 

the nest scrape and rim (Cramp 1985, Parnell et al. 

1995). Inter-nest distances vary from 0.3 to 20 m 

(Gochfeld and Burger 1996).

Reproductive phenology.—The following breeding 

information has been taken from Parnell et al. 

(1995), except where noted. In California, Gull-billed 

Terns generally arrive in mid-March to early April, 

but may arrive as early as the first week of March 

at the Salton Sea. Egg laying usually begins by midApril to early May in California and Baja California 

(Molina and Garrett 2001) and is presumed to 

be the same in western Mexico. Nesting by Gullbilled Terns at the Salton Sea may occur as late as 

mid-July through early August and is presumed 

to involve re-nesting attempts. In Atlantic Coast 

colonies, most egg laying begins from mid-May to 

early June. Both sexes participate in incubation, a 

period lasting 21-23 days beginning with the first 

egg. Earliest hatching is in early May in the west; 

most hatching on the Atlantic Coast occurs in June 

(Eyler et al. 1999). Chicks may move away from the 

nest soon after hatching, depending on the degree 

of disturbance and vegetation around nest sites. 

In extreme heat, parents lead very young broods 

to loafing areas at the water’s edge (KCM). First 

flights occur at 28–35 days. Young are fed by both 

parents at least four weeks post-fledging.

Breeding site fidelity.—Breeding site fidelity of 

Gull-billed Terns has been reported to be weak in 

Virginia (Erwin et al. 1998b) and Europe (Cramp 

1985, Parnell et al. 1995). On the Pacific Coast, Gullbilled Terns often occupy colony sites for multiple 

years. They nested for five and 10 consecutive years 

at two sites at the Salton Sea (Molina 2004), 11 

consecutive years (except 2000) at San Diego Bay 

(R. T. Patton, pers. comm.), and since 1996 at Cerro 
Natual History 7

delivered to chicks in 1981 consisted of terrestrial 

orthopterans, arachnids, and assorted insects, while 

the remaining prey items were associated with 

marine (shrimp, crabs, and fish) or fresh or brackish 

water (odonates and frogs) habitats. In Louisiana, 

Gull-billed Terns feed on crayfish at Lake Charles in 

winter (Clement 1946).

Foraging Behavior

The following is from Parnell et al. (1995), except 

where noted. By virtue of their varied diet and 

their habit of exploiting insect and lizard prey in 

terrestrial habitats, Gull-billed Terns forage over a 

wide range of substrates. In terrestrial and aquatic 

habitats, Gull-billed Terns forage on the wing, with 

characteristic buoyant swoops down to the substrate 

to pluck prey from the surface or near surface. 

They may frequently hover over the surface when 

foraging into the wind. Aerial prey (swarming 

insects such as weevils or ladybird beetles) is taken 

directly from the air column. Unlike other terns, 

Gull-billed Terns rarely, if ever, plunge-dive for 

prey. Gull-billed Terns usually swallow small items 

in flight but may land to manipulate or disarticulate 

larger items (Molina and Marschalek 2003). 

Both parents feed young, although the relative 

contributions of the sexes have not been quantified.

Gull-billed Terns are known to kleptoparasitize 

breeding Black Skimmers (Rynchops niger) in 

Texas (D. J. Newstead, pers. comm.), Common 

Terns (Sterna hirundo) in New Jersey (Parnell 

et al. 1995), and occasionally California Least and 

Forster’s terns (S. forsteri) in California (Molina 

and Marschelek 2003, B. E. Collins, pers. comm.).

Pemberton (1922) reported foraging distances of up 

to 22.5 km from Gull-billed Tern nesting colonies 

in Texas. Regular foraging distances of up to 9 km 

away from the nesting colony occurred in San Diego 

Bay (Molina and Marschelek (2003). Gull-billed 

Terns were observed foraging in areas up to 76 km 

north of the San Diego Bay nesting colony 

(B. Foster, pers. comm.), but it is unknown if these 

birds were active breeders.

Post-breeding Dispersal

Gull-billed Terns gather in small groups at 

river deltas, estuaries, sandy beaches, flooded 

agricultural fields, and inundated salt flats after 

young fledge. In California and Baja California, 

post-breeding movement may begin as early as 

mid-July with most, if not all, birds leaving breeding 

areas by mid- to late August (Parnell et al. 1995). 

Along the Atlantic Coast, Gull-billed Terns are one 

of the earliest of the terns to disperse from breeding 

colonies, often as early as late July (RME).

Predators.—Known predators of eggs or chicks of 

Gull-billed Terns in North America are raccoons 

(Procyon lotor), coyotes (Canis latrans), feral 

dogs (C. lupus familiaris) and cats (Felis catus), 

rats (Rattus spp.), Peregrine Falcons (Falco 

peregrinus), Laughing (Larus atricilla), California 

(L. californicus), Herring (L. argentatus) and 

Great Black-backed (L. marinus) gulls, Burrowing 

(Athene cunicularia) and Great Horned (Bubo 

virginianus) owls, and ghost crabs (Ocypode 

quadrata) (Blus and Stafford 1980, Parnell et al. 

1995, Eyler et al. 1999, O’Connell and Beck 2003). 

Other potential predators of eggs or chicks could 

be red foxes (Vulpes vulpes), skunks (Spilogale 

putorius and Mephitis mephitis), ground squirrels 

(Spermophilus spp.), Western (L. occidentalis), 

Yellow-footed (L. livens) and Heermann’s 

(L. heermanni) gulls, large herons (Ardeidae), 

American Kestrels (F. sparverius), Common 

Ravens (Corvus corax), and American Crows 

(C. brachyrhynchos) (Parnell et al. 1995, GonzalezBernal et al. 2003).

Diet.—The diet of Gull-billed Terns, composed of 

vertebrate and invertebrate prey, is broader than 

most other species of terns. They are opportunistic 

feeders on a variety of terrestrial and aquatic 

animals; invertebrate prey of terrestrial and 

aquatic origin appears to dominate their diets. 

At San Diego Bay, small marine invertebrates, 

primarily mole crabs (Emerita analoga), and 

small fish were the dominant prey items delivered 

by adults to chicks, comprising 43% and 25%, 

respectively, of all deliveries observed in 2002 

(Molina and Marschalek 2003). Additional diet 

items included common side-blotched (Uta

stansburiana) and western fence (Sceloporus

occidentalis) lizards, insects, and small chicks of 

Black-necked Stilts (Himantopus mexicanus), 

Killdeer (Charadrius vociferous), western Snowy 

Plovers (C. alexandrinus nivosus), and California 

Least Terns (Sternula antillarum browni). At the 

Salton Sea, 49% of prey items delivered to chicks in 

2001 were insects [orthopterans (mainly crickets), 

odonates, and hymenoptera], with small fish 

(Tilapia) comprising 41% (KCM). Other food items 

delivered, listed in descending order of importance, 

were amphibians, crayfish, and small Black-necked 

Stilt chicks. Additional prey items taken at the 

Salton Sea include common side-blotched lizards 

and periodically abundant insects such as cicadas, 

butterflies, weevils, and ladybird beetles. In the Gulf 

of California and mainland Mexico, Gull-billed Terns 

feed on fiddler crabs (Uca spp.) and farmed shrimp 

(KCM). In Virginia, small marine invertebrates 

(primarily fiddler crabs), fish, and insects (primarily 

large odonates and orthopterans) were the 

dominant prey items fed to chicks in 1995 and 1996 

(Erwin et al. 1998a). In Lavaca Bay, Texas, Quinn 

and Wiggins (1990) reported that 47.5% of prey 
8 Status Review and Conservation Recommendations for the Gull-billed Tern

Population Estimates and Trends

above and difficult to account for inter-annual 

movements. In no single year have all states with 

colonies been surveyed simultaneously, and during 

the years 2000 to 2004 most states have reported 

counts for only one year (Table 2). To estimate total 

numbers in recent years (2000–2004), we summed 

the mean counts for all states with breeding colonies 

and the highest count for each state during this 

period (Table 2). The resulting population estimates 

for G. n. aranea for 2000–2004 are 3608 pairs (sum 

of mean counts) and 4432 pairs (sum of high counts).

Although Gull-billed Terns are known to breed 

in the large lagoon system of Laguna Madre in 

Tamaulipas, Mexico (Garza-Torres and Navarro 

S. 2003), no historic or recent population estimates 

are available. A preliminary survey in 2005 in the 

state of Veracruz did not locate active colony sites 

(EM); no other comprehensive survey in Mexico has 

been conducted.

Gelochelidon nilotica vanrossemi.—The earliest 

available assessment of the historical population 

size of G. n. vanrossemi in the U.S. is Pemberton’s 

(1927) estimate of 500 pairs nesting at the Salton 

Sea’s south end in 1927. By 1937, fewer than 200 

pairs nested there (Grinnell and Miller 1944). This 

decline continued through the 1950s and 1960s with 

60 pairs in 1952, 75 pairs in 1957, 40-50 pairs in 1959, 

and just a few pairs through the 1960s (Remsen 

1978). By 1976 only 17 pairs nested at the Salton 

Sea (McCaskie 1976) and twice this number may 

have nested in 1977 (Remsen 1978). During the 

1980s, the largest count reported was a minimum of 

75 pairs in 1986 (McCaskie 1986).

In 1986, Gull-billed Terns colonized a single site on 

the California coast at the saltworks in southern 

San Diego Bay, which became part of the San Diego 

Bay National Wildlife Refuge (NWR) in 1999. This 

colony increased to 30 pairs in 1992, varied between 

eight and 20 pairs through the remainder of the 

1990s, and steadily climbed from approximately 24 

pairs in 2000 to 54 pairs in 2006 (R. T. Patton, pers. 

comm.). The species has not established colonies at 

any other location in coastal California or away from 

the Salton Sea. During the early 1990s, an average 

of 120 pairs of Gull-billed Terns nested at the Salton 

Sea and San Diego Bay NWR (Clapp et al. 1993, 

Parnell et al. 1995). From 1997 to 2004, an average 

of 146 pairs nested in California at these two sites 

(Table 3).

Gull-billed Terns are not considered to be abundant 

anywhere in their North American range (Parnell 

et al. 1995, Gochfeld and Burger 1996). There 

are few historical population estimates for either 

subspecies in North America, especially for 

Mexico. When state census data are available, 

they often have not been collected simultaneously 

throughout an entire region. We compiled published 

and unpublished results of surveys conducted 

throughout the U.S. and western Mexico to gain 

a more complete and updated understanding of 

current population levels for both subspecies in 

North America over the last two decades.

Estimates

Spendelow and Patton (1988) estimated 5400 

Gull-billed Terns for the entire U.S. from 1976 

to 1982, which when converted using Erwin’s 

(1979) pairs-to-adults conversion factor of 0.66, 

yields 3563 pairs. This estimate excluded birds in 

California (Spendelow and Patton 1988) and may 

underestimate the population in Florida (Parnell 

et al. 1995); thus underestimating the entire 

U.S. population.

Gelochelidon nilotica aranea.—For the 

southeastern U.S. (excluding Virginia and the 

Florida Gulf of Mexico coasts), Clapp et al. (1983) 

reported 3472 Gull-billed Terns from 1972 to 1979. 

For ease of comparison, we use Erwin’s (1979) 

pairs-to-adults conversion factor to convert Clapp 

et al.’s (1983) estimate of individuals into 2292 pairs. 

Portnoy et al. (1981) estimated 1314 Gull-billed 

Terns in North Carolina south to Atlantic Florida; 

Kress et al. (1983) equated this figure to 650 pairs. 

Clapp and Buckley (1984) estimated a total of 

3019 pairs of Gull-billed Terns along the southern 

Atlantic and Gulf of Mexico coasts between 1976 and 

1983. For the north and mid-Atlantic Coast in 1982, 

Buckley and Buckley (1984) reported a probable 

1000 pairs; yielding 4019 pairs for the entire eastern 

U.S. when combined with Clapp and Buckley’s 

(1984) total. In summary, population estimates for 

the G. n. aranea subspecies in the U.S. from 1976 to 

1983 ranged from about 3563 to 4019 pairs.

The lack of systematic survey efforts in all states 

with G. n. aranea colonies makes it difficult to 

compare recent population sizes with those reported 
Population Estimates and Trends 9

Table 2. Number of breeding pairs and colony sites of G. n. aranea in the continental United States for years 

in which comprehensive state-wide censuses were conducted.

Year No. of No. of Avg. Pairs/ 

Pairs Colonies Colony

Atlantic Coast 

New York

1977 0 0 —

1985 2 2 1

1995 2 1 —

2003 11 3 4

New Jersey

1977 19 4 5

1985 17 3 5

1995 18a 3 6

2001 92a 5 18

Virginia

1977 729a 11 66

1984 413 11 38

1993 265 15 18

1998 310 15 21

2003 293 16 18

North Carolina

1977 621 21 30

1985 174 4 44

1995 249 10 25

2001 258 7 37

South Carolina

1976 154a 4 39

1988 254 10 25

1995 165 8 21

2003 239 7 34

Georgia

1995 80 1 —

2003 54 1 —

Florida

1975 534 2 267

1980–1985b 75c 6–8 —

2000 17 3 6

Gulf Coast 

Alabama

1976d 23 1 —

2001e 87 3 29

2002e 50 1 —

2003e 9 1 —

2004e 85 3 28

Mississippi

1976d 2 1 —

1994f 0 0 —

1995f 0 0 —

1996f 2 1 —

1997f 1 1 —

1998f 0 0 —

1999f 0 0 —

2000f 0 0 —

2001f 0 0 —

2002f 5 1 —

Year No. of No. of Avg. Pairs/ 

Pairs Colonies Colony

Mississippi (cont’d)

2003f 2 1 —

2004f 150 1 —

Louisiana

1976d 154 4 39

1990g 161 3 54

1991h 30 1 —

1992h 350 2 175

1993h 650 3 217

1994h 290 4 73

1995h 400 3 133

1996h 173 4 43

1997h 248 11 23

1998h 1120 5 224

1999h 590 5 118

2001i 440 4 110

Texasj

1973c 2187 27 81

1974c 688 17 41

1975c 1289 23 56

1976 1098 21 52

1977 1632 32 51

1978 2034 30 68

1979 2267 38 60

1980 1810 33 55

1981 2046 39 53

1982 2123 40 53

1983 4661 33 141

1984 2416 47 51

1985 1926 42 46

1986 1075 32 34

1987 1946 38 51

1988 1243 36 35

1989 1150 40 29

1990 2868 37 78

1991 913 21 44

1992 1372 35 39

1993 1553 34 46

1994 3706 41 90

1995 2553 28 91

1996 914 37 25

1997 1576 36 44

1998 2293 41 56

1999 846 29 19

2000 2791 39 72

2001 1840 36 51

2002 2565 39 66

2003 1292 29 45

d Portnoy 1977

e R. B. Clay, pers. comm.

f M. P. Stevens, pers. comm.

g Martin and Lester 1990

h G. D. Lester, pers. comm.

i Michot et al. 2004

j U.S. Fish and Wildlife 

Service 2004

a Breeding pairs estimated 

from counts of individuals by 

multiplying individuals by 0.667.

b Smith and Alvear 1997

c Minimum estimate due to 

incomplete state survey 

coverage.
10 Status Review and Conservation Recommendations for the Gull-billed Tern

Historical estimates of Gull-billed Terns breeding 

along the Pacific coast of Mexico are unavailable. A 

total of 367 potential nesting sites were surveyed 

in 2003, with an estimated total of 376 nesting 

pairs of Gull-billed Terns distributed among seven 

colonies in western Mexico (EM, EP). In 2005, 

Palacios and Mellink (2007) and KCM documented 

550 to 551 breeding pairs among six of the seven 

breeding locations documented in 2003 and at one 

additional site. Combined with the number of pairs 

in California, 737 to 808 pairs of G. n. vanrossemi

appear to have nested in western North America in 

2003 and 2005 (Table 3).

Trends

Gelochelidon nilotica aranea.—The numbers of 

breeding Gull-billed Terns along the northern 

Atlantic coast are small, but seem to be stable or 

increasing slightly, while numbers along the midand southern Atlantic coasts have declined since 

the mid- to late 1970s (Table 2). In Virginia, partial 

surveys in 1975 and 1976 recorded high totals of 

1485 and 1333 pairs, respectively, and a complete 

survey in 1977 recorded 729 pairs (Brinker et al. 

2007, 2008). In North Carolina, declines occurred 

between 1975 and 1976 and the mid-1980s, with 

numbers remaining at about a third of the state’s 

mid-1970s levels (D. H. Allen, pers. comm.). In 

Florida, a relatively large number of breeding 

Gull-billed Terns (534 pairs in 1975) appeared 

to have dwindled to just a few pairs, although 

comprehensive surveys of the state have been 

infrequent (Table 2; Smith and Alvear 1997). The 

number of pairs in South Carolina appears to be 

stable or increasing slightly, while the population 

in Georgia may be declining (Table 2). In Maryland 

and Delaware, the species is possibly extirpated. 

The number of pairs breeding in Delaware has 

historically been small, and no breeding has been 

documented since 1991 (D. B. Carter, pers. comm.). 

The number of pairs in Alabama, Mississippi, 

and Louisiana are small, but apparently stable or 

increasing slightly (Table 2; Portnoy 1977, R. B. 

Clay and M. P. Stevens, pers. comm.). In Texas, 

where the largest known breeding concentrations 

in North America occur, Gull-billed Tern numbers 

appear to have remained stable overall since the 

early 1970s (Table 2).

Gelochelidon nilotica vanrossemi.—Although 

declines were apparent from the late 1930s through 

the late 1970s at the Salton Sea, the small number of 

breeding pairs in California seems to have remained 

stable since the early 1990s (Table 3; KCM). In 1986, 

Gull-billed Terns increased their numbers slightly 

by colonizing one coastal site at San Diego Bay. No 

trend information is available for Mexico (KCM).

Table 3. Number of breeding pairs and colony sites 

of G. n. vanrossemi in the Pacific Coast of the 

United States and Mexico in years surveys were 

conducted. 

Year No. of No. of Avg. Pairs/ 

Pairs Colonies Colony

United States 

Californiaa

1992 136 4 34

1993 131 4 33

1994 113 4 28

1995 92 3 27

1996b 155 3 55

1997 162 3 53

1998 131–133 3 —

1999 112–122 3 —

2000 135–142 4 —

2001 173 2 87

2002c 97–101 2 —

2003 187–192 4 —

2004 157 2 79

2005 252–257 5 —

Mexicod,e 

Baja California

2003 183 2 92

2004 234 2 —

2005 274 2 137

Baja California Sur

2003 14 1 —

2005 10 1 —

Sonora

2003 0 0 —

2005 0 0 —

Sinaloa

2003 15 1 —

2005 26–27 2 14

Nayarit

2003 122–152 2 —

2005 185 2 93

Colima

2003 15 1 —

2005 55 5 11

a Data for Salton Sea: 1992 to 2001 from Molina 2004; 2002 to 

2005 from KCM. Data for San Diego: 1992 to 2005 from R. T. 

Patton, pers. comm.

b Data from Salton Sea colonies only.

c Data from San Diego and some Salton Sea colonies.

d Data from Palacios and Mellink 2007, except Baja California 

(2004) from KCM.

e Palacios and Mellink 2007 also surveyed Jalisco, Michoacán, 

Guerrero, Oaxaca, and Chiapas but reported no breeding.
Monitoring Activities 11

Monitoring Activities

and may include Gull-billed Terns. New Jersey, 

North Carolina, and Georgia conduct periodic 

surveys of breeding waterbird colonies including 

Gull-billed Terns (C. D. Jenkins, S. E. Cameron, 

and J. S. Calver, pers. comm.). In Florida, the only 

monitoring efforts conducted recently for Gullbilled Terns were those directed toward the state 

breeding bird atlas (J. A. Rodgers, pers. comm.). 

State breeding bird atlases documenting Gull-billed 

Tern colonies were published for New York (Bull 

1964), New Jersey (Walsh et al. 1999), Maryland 

(Brinker 1996), Mississippi (Gandy and Turcotte 

1970), and Louisiana (Michot et al. 2004), and an 

atlas is currently under development in Alabama 

(KCM). A preliminary survey in the state of 

Veracruz in Mexico in 2005 yielded no colony sites 

(EM). Comprehensive surveys in coastal eastern 

Mexico for G. n. aranea have not been conducted.

To facilitate coordinated comprehensive survey 

efforts, the USFWS sponsored the development of 

field identification cards (in English and Spanish) 

and a bi-national workshop in 2003 to address a 

standardized survey protocol for G. n. vanrossemi. 

The USFWS also sponsored the first comprehensive 

surveys for G. n. vanrossemi in Mexico in 2003 and 

2005, which combined with annual monitoring in 

California, resulted in the first range-wide surveys 

for this subspecies.

Breeding Bird Survey

The Breeding Bird Survey (Sauer et al. 2008) does 

not adequately monitor this species because survey 

routes do not adequately represent Gull-billed Tern 

breeding areas in coastal estuarine habitats (KCM). 

Gull-billed Terns were not included in Breeding 

Bird Survey trend analysis by Price et al. (1995).

Regional and State Surveys

There are no coordinated breeding or winter 

surveys of Gull-billed Terns throughout their entire 

range in the United States or in North America. 

The Gulf of Mexico coasts of Alabama, Mississippi, 

and Louisiana were occasionally surveyed as a 

region; this survey was last conducted in 1976 

(Portnoy 1977). Known Gull-billed Tern colony sites 

are monitored annually in California and Virginia 

(RME, KCM). In Texas, Mississippi, Alabama, 

South Carolina, and New York, Gull-billed Tern 

colonies are monitored annually as part of each 

state’s comprehensive waterbird nesting surveys 

(P. Glass, M. P. Stevens, R. B. Clay, T. M. Murphy, 

and M. R. Wasilco, pers. comm.). Louisiana conducts 

comprehensive surveys of nesting waterbirds at 

least every four years (P. L. Leberg, pers. comm.), 

Matt Sadowski©
12 Status Review and Conservation Recommendations for the Gull-billed Tern

Habitat Requirements

Winter and Summer 

Non-breeding Seasons

Wintering Gull-billed Terns along the Gulf of 

Mexico Coast are generally found in estuaries, salt 

and freshwater marshes, canals, and ponds. Away 

from the coast, this species is commonly observed 

in flooded agricultural fields (rice and crayfish 

impoundments). In western Mexico, Gull-billed 

Terns are usually found in bays and estuaries with 

extensive tidal flats, agricultural fields, canals 

and drains, salinas (salt mines), and aquaculture 

(primarily shrimp) impoundments (KCM) and use 

exposed dikes for courtship displays (EP). Away 

from the coastal lowlands on the Pacific Coast, small 

numbers of Gull-billed Terns are regularly found in 

winter near Laguna Sayula in Jalisco, an ephemeral 

wetland at the extreme southwest corner of the 

Mexican Plateau (Howell 1999).

Breeding Season

In North America, Gull-billed Terns typically 

nest on barrier islands, dredged-material islands, 

constructed islets or isolated levees in wildlife, 

salt extraction, and aquaculture impoundments, 

shell bars and islands in open marshes, abandoned 

causeways, natural islets in shallow tidal and 

brackish lagoons, and sand and shellbars in river 

deltas (Parnell et al. 1995). Nesting substrates 

include bare sand, gravel, crushed shell, and silty 

clay soils. Nest sites generally lack vegetation, 

but when present, it is usually low and sparse. In 

Texas, Gull-billed Terns have nested in dense areas 

of the grasses Paspalum and Monanthochloe (J. 

K. Wilson, pers. comm.) and in Virginia, the largest 

colony is on wrack (drifted rafts of dead Spartina) 

on a low island in a salt marsh. In western Mexico, 

Gull-billed Terns nest on low islands with mangrove 

or cactus and on mud flats with salt marsh 

vegetation. Gull-billed Terns have occasionally 

nested on gravel rooftops in coastal Texas (P. Glass, 

pers. comm.), Louisiana (Purrington 2002), 

and Florida (Coburn 1996).

Inland, nesting occurs on natural and constructed 

islands in saline and freshwater lakes, reservoirs, 

and impoundments, and on abandoned oil and gas 

causeways (Parnell et al. 1995, Molina and Garrett 

2001, Molina 2004). In Florida, Gull-billed Terns 

have nested on sand fill in phosphate mine pits 

(Smith and Gore 1996). In the Mexican Central 

Plateau, one or two pairs (of either subspecies) have 

been observed nesting above 2200 m elevation at 

Lake Xochimilco and Lake Texcoco; these are the 

only North American breeding records significantly 

above sea level (Molina and Erwin 2006).

Whether on the coast or inland, colony sites are 

typically located near optimal foraging habitats, 

which include the shallow margins of bays, 

rivers, and marshes, exposed mudflats, the tidal 

margins of sandy beaches, agricultural fields and 

drains, wildlife, salt extraction, and aquaculture 

impoundments, sandy lake shores, and open 

shrublands.

Kathy Molina©
Threats 13

Habitat Loss and Degradation

Vegetation succession and erosion can alter the 

suitability of colony sites on dredged-material 

islands along the Gulf of Mexico (Chaney et al. 

1978) and Atlantic coasts (Parnell and Soots 1979). 

Changes in the distribution of ground-nesting 

waterbirds from 1977 to 1995 in New Jersey, 

Virginia, and North Carolina coincided with changes 

in dredging policy along the mid-Atlantic (Erwin 

et al. 2003). Since the 1980s, competing demands 

by coastal communities for sand augmentation for 

beaches has slowed the rate of replenishment of 

dredged-material islands allowing the establishment 

of dense and woody vegetation or the erosion and 

disappearance of former colony sites (Erwin et al. 

2003). In North Carolina, the number of Gull-billed 

Terns nesting on dredged-material islands declined 

from 524 pairs in 1977 to only 128 pairs in 1995 

(Erwin et al. 2003). Parnell et al. (1997) attributed 

the low nesting site fidelity and high rates of site 

turnover exhibited by Gull-billed Terns in 

North Carolina from 1977 to 1995 to the 

degradation of colony sites due to vegetation 

succession and erosion.

Increases in predator populations on Atlantic Coast 

barrier islands are believed responsible for the 

diminished suitability of these sites for Gull-billed 

Terns and other colonial ground nesting birds since 

the 1980s, especially in Virginia (Erwin et al. 2001, 

2003) where, although the number of colonies has 

increased, the size of each and the overall number 

of breeding Gull-billed Terns has declined (Erwin et 

al. 2003). Fragmentation of larger colonies into more 

numerous but smaller ones does not necessarily 

increase successful reproduction as smaller colonies 

may be less resistant or resilient to predation and 

human disturbances (Sears 1979, Wittenberger and 

Hunt 1985).

Diminishing freshwater and agricultural inflows to 

the Salton Sea have resulted in lower water levels 

and the bridging of once isolated islands, rendering 

them accessible to mammalian predators and 

unsuitable for nesting. Water levels may be reduced 

even further by conservation measures under 

the Imperial Irrigation District’s water transfer 

program (J. A. Bartel, pers. comm.).

Threats

Nesting attempts by Gull-billed Terns at Isla 

Montague in Mexico were consistently interrupted 

by regular tidal inundations throughout the 1993 

and 1994 breeding seasons (Peresbarbosa and 

Mellink 2001). During the 2004 and 2005 breeding 

seasons, complete colony failures were attributed to 

non-storm related tidal inundations (KCM). Since 

the completion of upstream dams and diversions 

on the Colorado River in the 1930s and 1940s, this 

estuary island no longer receives the sediment 

load that prevailed prior to the damming of the 

river. Lacking such sediment replenishment, it is 

subjected to the erosion forces of Gulf of California 

tides (Alvarez-Borrego 2001).

The recent large scale conversion of estuarine 

habitats to commercial aquaculture (shrimp and 

oyster farms) in northwestern mainland Mexico 

(Páez-Osuna et al. 2003) may reduce or degrade 

available mudflats for foraging, while providing 

novel and concentrated food sources during the 

breeding season (Molina et al. 2009). Shrimp are 

generally harvested in the fall and winter, removing 

this food source for wintering Gull-billed Terns 

(Molina et al. 2009). Since 1989, the extent of 

wetlands converted to aquaculture in Sonora has 

increased some 3000% to encompass nearly 7500 

ha of shrimp farms; in Sinoloa, approximately 1300 

ha have been dedicated to aquaculture (Instituto 

Tecnologico de Sonora 2004). Loss of estuarine 

habitat in Mexico has also occurred through the 

construction of marinas and other tourism-related 

development and saltworks (KCM).

Overutilization

Overutilization (such as egging and over-hunting) 

is not a known threat to Gull-billed Terns.
14 Status Review and Conservation Recommendations for the Gull-billed Tern

Inadequacy of Existing 

Regulatory Mechanisms

Despite the protections and status designations 

denoting conservation concern at the Federal, state, 

and BCR scale, the species has continued to show 

declines in recent decades in the Atlantic Coast 

region, particularly in Virginia, North Carolina, 

Maryland and Florida (Table 2; Smith and Alvear 

1997, R. B. Clay, pers. comm., RME). Populations in 

Texas have remained large and stable despite the 

lack of additional regulatory measures, apparently 

due to the large number of dredged material nesting 

sites in this state (KCM).

Other Natural or Manmade Factors

Storm events and other natural disturbances.—

Colony sites on the Atlantic Coast are frequently 

flooded by abnormally high spring tides as well 

as storm events, resulting in high rates of nest 

loss, particularly at marsh nesting sites (Erwin et 

al. 1998b). Major hurricanes have had dramatic 

adverse impacts to nesting habitats in the Gulf of 

Mexico, as many sites have simply disappeared (W. 

J. Vermillion, pers. comm.). Spring tides regularly 

wash out entire nesting colonies in the Gulf of 

California at Isla Montague in Baja California and 

Isla El Rancho in Sinaloa, Mexico (Peresbarbosa 

and Mellink 2001, X. Vega, pers. comm.). Gull-billed 

Terns failed to re-nest at Isla Montague and Isla El 

Rancho in 2004 and 2005 after late April high tides 

flooded first attempts (KCM).

Pesticides or other contaminants.—There is limited 

information available on the exposure of Gull-billed 

Terns to contaminants. Residue levels of DDE in 

11 Gull-billed Tern eggs collected in South Carolina 

in 1972 ranged from 0.28 to 10.71 μg per g (wet 

wt.) (Blus and Stafford 1980). Two eggs from the 

1972 sample containing the highest residue levels 

(8.75 and 10.71 μg per g) had abnormal and fragile 

shells. The ranges of DDE residues in Gull-billed 

Tern eggs from South Carolina sampled in 1974 

(n =14 eggs) and in 1975 (n = 5 eggs) declined to 

0.18-1.34 μg per g and 0.14-0.38 μg per g (wet wt.), 

respectively (Blus and Stafford 1980). The mean 

eggshell thickness for the 1972, 1974, and 1975 

samples ranged between 0.220 mm to 0.227 mm 

and was not significantly different from the mean 

thickness of 0.228 mm for four pre-1947 Gull-billed 

Tern eggs (Blus and Stafford 1980). Residues of 

polychlorinated biphenyls, oxychlordane, dieldrin, 

and trans-nonachlor were low or undetectable in 

Gull-billed Tern eggs sampled between 1972 and 

1975 (Blus and Stafford 1980).

Disease and Predation

No information exists regarding disease or 

parasites (Parnell et al. 1995). Gull-billed Terns 

seemed unaffected by the large outbreaks of 

botulism, cholera, and other diseases that occurred 

at the Salton Sea during the 1990s (KCM).

Low reproductive success of Gull-billed Terns in 

Virginia is in part attributed to predation on eggs 

and chicks by gulls and Great Horned Owls (Eyler 

et al. 1999, O’Connell and Beck 2003). O’Connell and 

Beck (2003) reported that 77% of 133 eggs among 

64 Gull-billed Tern nests in Virginia were lost to 

predation by Herring and Great Black-backed gulls. 

Nesting by Gull-billed Terns on traditional barrier 

island sites has become more limited in New Jersey 

and Virginia due to red fox and raccoon expansions 

(Erwin et al. 2001).

Receding water levels have caused traditional 

nesting sites at the Salton Sea to become 

increasingly accessible to mammalian predators, 

resulting in complete breeding failures at the 

Morton Bay colony in 2004 and 2005 (KCM). The 

colonization of the Salton Sea and subsequent 

breeding by California Gulls in 1996 adversely 

affected Gull-billed Tern nesting and fledging 

success (Molina 2004). From 1997 to 2001, Gullbilled Terns ceased nesting at the Obsidian Butte 

colony and on two islands at the Sonny Bono Salton 

Sea NWR while these sites were occupied by 

California Gulls (Molina 2004). Gull-billed Terns 

reoccupied the Obsidian Butte colony site in 2004 

when California Gulls ceased to nest there (KCM).

Feral dogs and cats and introduced rats are 

also threats to colonies in or close to urban 

environments. At the San Diego Bay NWR, Gullbilled Terns do not nest on isolated islands, but 

instead occupy sites among a network of easily 

accessible earthen levees where an aggressive 

predator control program reduces mammalian 

predation (B. E. Collins, pers. comm.).
Threats 15

The geometric mean concentration of selenium 

for six Gull-billed Terns eggs collected from the 

Salton Sea in 1991 was 4.10 ppm (dry wt., range 

= 3.4 to 5.3; D. J. Audet, pers. comm.) below the 

threshold for lowered egg hatchability (Skorupa and 

Ohlendorf 1991). The concentration of total DDT 

from one Gull-billed Tern egg from San Diego Bay, 

California was considered elevated at 2.9 ppm (wet 

wt.), but below levels associated with reproductive 

impairment in other species (C. A. Roberts, pers. 

comm.). 2.9 ppm of DDT is approaching levels of 

severe effects in sensitive species (Blus 1984). The 

total PCB concentration in that egg was below 

the 2.9 ppm threshold at 1.8 ppm (wet wt.; C. A. 

Roberts, pers. comm.). Concentrations of arsenic, 

cadmium, chromium, copper, mercury, nickel, and 

zinc in the San Diego egg were below threshold 

levels (C. A. Roberts, pers. comm.).

The April 20, 2010 Deepwater oil rig disaster off 

the Louisiana coast dramatically demonstrated the 

actual and potential impacts of oil contamination 

on a wide range of coastal waterbirds, including 

Gull-billed Terns. Although they are less dependent 

on prey from marine and estuarine waters than 

other tern species, Gull-billed Terns along northern 

and eastern Gulf Coast, Florida, and the southeast 

Atlantic barrier islands are certainly at risk from 

oil-contaminated sand and marsh nesting and 

feeding habitats.

Population size and colony distribution.—The 

small population size and the low number and 

sizes of Gull-billed Tern breeding colonies in 

North America increases their vulnerability to 

catastrophic habitat change, human disturbances, 

flooding events, predation, displacement by 

other nesting species, and other natural and 

anthropogenic threats.

This is particularly true for G. n. vanrossemi, for 

which recent breeding is known at only one coastal 

California site, one to four sites in the Salton Sea, 

and six to eight widely separated sites in western 

Mexico. From 1992–2004, 65–90% of California’s 

annual breeding population nested at the Salton 

Sea, indicating a high degree of population 

consolidation in one area (Table 3). Two other 

areas of consolidation occur in western Mexico, 

at Cerro Prieto and Isla Montague in Baja 

California and at Laguna Pericos in Nayarit. 

These few sites support a high percent of the 

G. n. vanrossemi population (KCM). G. n. aranea

colonies are also small and localized on the Atlantic 

Coast with an area of consolidation from Virginia 

to South Carolina (RME).

Introduced species.—Predation by feral dogs 

and cats and introduced rats is discussed in the 

Disease and Predation section (above). The 

encroachment of invasive plants, salt cedar 

(Tamarisk spp.) and common reed (Arundo and 

Phragmites spp.), degrades nesting habitat at 

Salton Sea colonies (KCM).

Conflicts with other species.—In San Diego County, 

California, Gull-billed Terns have been observed to 

prey upon the eggs and chicks of two species listed 

under the Endangered Species Act (ESA), the 

threatened western Snowy Plover and endangered 

California Least Tern, since 2001 (R. T. Patton, pers. 

comm.). The highest number of observed predation 

events was in 2003, when 52 chicks of California 

Least Terns and western Snowy Plovers were 

taken. Additional predation was documented by the 

presence of California Least Tern chick leg bands 

in Gull-billed Tern nests (J. A. Bartel, pers. comm.). 

Not all predation events are directly observed, and 

more events are suspected (R. T. Patton, 

pers. comm.).

Between 1993 and 1995, conflicts with California 

Least Terns and western Snowy Plovers in southern 

California resulted in the lethal control of six Gullbilled Tern adults under the MBTA (T. E. TateHall, pers. comm.). No additional lethal control of 

Gull-billed Terns in response to such conflict has 

been authorized or reported. Little information 

is currently available on the overall impact of 

predation by Gull-billed Terns on California Least 

Terns and western Snowy Plovers. Implementation 

of regular or long-term lethal control of Gull-billed 

Terns to protect California Least Terns and Snowy 

Plovers may affect the stability or growth of the 

Gull-billed Tern population in southern California.

Gull-billed Tern predation on Least Terns is not as 

evident in areas outside of southern California. Gullbilled Terns frequently share nesting colonies with 

Least Terns at Isla Montague, with no evidence 

of such predation (KCM). Gull-billed Terns have 

been noted to forage near a colony of Least Terns 

in Gulfport, Mississippi and predation of one chick 

was documented (Densmore 1990). Gull-billed Terns 

were observed to swoop on Least Tern chicks in 

Florida but capture was never observed (Smith and 

Gore 1996). Gull-billed Terns didn’t include avian 

prey in their diet in Virginia (Erwin et al. 1998a).

Other interspecific interactions.—Black Skimmers 

have damaged and/or caused Gull-billed Tern nests 

to be abandoned, and were suspected of inflicting 

lethal lacerations to Gull-billed Tern chicks at 

San Diego Bay (R. T. Patton, pers. comm.). At the 

Salton Sea, loafing Brown (Pelecanus occidentalis) 

and American White (P. erythrorhynchos) pelicans 

caused high rates of nest loss and abandonment of 

several Gull-billed Tern colonies (KCM). In early 

spring 2007, Caspian Terns (Hydroprogne caspia) 

began nesting on islands at the Salton Sea typically 

used by breeding Gull-billed Terns, precluding the 

later arriving Gull-billed Terns from nesting (C. C. 

Schoneman, pers. comm.). In Virginia, competition 

with Herring and Great Black-backed gulls for nest 

sites among higher elevation habitats force Gullbilled Terns and other small larids to nest in flood 

prone areas (O’Connell and Beck 2003).
16 Status Review and Conservation Recommendations for the Gull-billed Tern

Aggressive anti-predator defenses of Gull-billed 

Tern are well known (Sears 1978, Parnell et al. 1995) 

and may benefit colony associates that show less 

aggressive defense (Pius and Leberg 1997, 1998). 

Black Skimmers may benefit from the aggressive 

nest defense of Gull-billed Terns by nesting in or 

near Gull-billed Tern colonies (Burger and Gochfeld 

1990, Pius and Leberg 2002). In Florida, Gullbilled Terns frequently co-occupy nesting colonies 

with Least Terns (Smith and Gore 1996). In mixed 

species colonies, the smaller Least Tern may also 

benefit from G. n. aranea’s aggressive response to 

predators.

Other conflicts.—The Gull-billed Tern’s ability to 

use a variety of terrestrial habitats when foraging 

resulted in conflicts with military aircraft operations 

at the Naval Base, Coronado and Naval Outlying 

Landing Field, Imperial Beach in San Diego Bay. 

In 2004, two foraging adults were lethally removed 

near an active runway on the Naval Base; and in 

2007, one adult was lethally removed at the Naval 

Outlying Landing Field (T. E. Tate-Hall, pers. 

comm.). These birds were removed under the 

authority of a Bird Airstrike Hazard permit under 

the MBTA (T. E. Tate-Hall, pers. comm.).

In Mexico, Gull-billed Terns forage extensively over 

commercial shrimp farms during harvest. Although 

lethal control of predators is not legally authorized 

in Mexico, it does occur (KCM); however, data on 

potential impacts are unavailable.

Disturbance to nesting sites.—Human disturbances, 

especially when frequent or prolonged, threaten 

reproductive success by exposing eggs and young 

to opportunistic predators or to lethal temperatures 

(Parnell et al. 1995). Gull-billed Tern chicks are 

highly precocial and will move long distances from 

the nest site, frequently over water, when disturbed 

repeatedly, potentially resulting in mortality from 

drowning or from immobilization in soft silty 

substrates (KCM). Human and pet disturbances 

at nesting colonies are potentially severe in 

Florida (Smith and Gore 1996) and Alabama, and 

are increasing in Virginia and North Carolina 

(Parnell et al. 1997). Management to reduce human 

disturbance has likely contributed to the presence, 

and in some cases persistence, of Gull-billed Tern 

colonies on NWRs and other managed state and 

federal lands (KCM).

Flickr/marj_k©
Management and Conservation 17

Predator Management

Predator control, whether by lethal or non-lethal 

measures (e.g. fencing, predator relocation, etc.) 

can directly benefit Gull-billed Terns and other 

ground nesting colonial waterbirds at nearby 

colonies. In Virginia, control (removal) of foxes and 

raccoons is conducted on selected barrier islands 

(RME). Control of avian and mammalian predators 

is implemented annually at the San Diego Bay 

NWR for recovery of California Least Terns and 

western Snowy Plovers, incidentally benefiting 

Gull-billed Terns (B. E. Collins, pers. comm.). A 

mammalian predator control program is proposed 

to protect Gull-billed Tern colonies at the Sonny 

Bono Salton Sea NWR (C. C. Schoneman, pers. 

comm.). Currently, predator control is occurring at 

waterbird colonies located on private lands in the 

Salton Sea area (C. C. Schoneman, pers. comm.).

Chain-link and electric fencing is used at East Lake 

colonies at the Lower Rio Grande Valley NWR 

in Texas to exclude mammalian predators from 

waterbird nesting areas (D. S. Stolley, pers. comm.). 

Electric fencing is also used at Sonny Bono Salton 

Sea NWR to exclude predators, primarily raccoons.

Habitat Management

Federal and state wildlife agencies and conservation 

organizations implement a variety of management 

actions to protect Gull-billed Tern colonies. At 

some colony locations, signs are posted or barriers 

are constructed to eliminate human disturbance. 

At a few colonies in Virginia, New Jersey, Texas, 

and California, experiments have been attempted 

with electric and traditional fencing to exclude 

mammalian predators. These efforts, and others to 

control the encroachment of vegetation at nest sites, 

have reduced threats of habitat modification and 

human disturbance (Smith and Gore 1996).

The Sonny Bono Salton Sea NWR manages water 

levels in freshwater impoundments to avoid shallow 

depths that allow access by mammalian predators, 

manages invasive vegetation (i.e., Tamarisk) to 

maintain open nesting habitat, and restricts public 

access to colonies to reduce human disturbance. 

The effectiveness of these management actions 

is evidenced by the early season abandonment 

of unmanaged colonies on adjacent private lands 

due to predator disturbances, and the subsequent 

relocation of these failed colonies to managed 

habitat in NWR impoundments (C. C. Schoneman, 

pers. comm.).

Isla Montague lies within the protective core zone 

of the Rio Colorado Delta Biosphere Reserve, but 

has no habitat management specifically directed 

at nesting Gull-billed Terns. Neither does Isla El 

Rancho, in Bahia Santa Maria, which is included in 

the Gulf of California Island Park System and the 

Santa Maria Bay Ecosystem Management Program 

(KCM). Sites in Nayarit and Colima also lack 

habitat management (EP).

Management and Conservation
18 Status Review and Conservation Recommendations for the Gull-billed Tern

Artificial Nesting Habitat

In 2005, at the Sonny Bono Salton Sea NWR, 

the USFWS experimented with a small floating 

raft in a freshwater impoundment to augment 

existing nesting habitat (C. C. Schoneman, pers. 

comm.). Gull-billed Tern decoys and a sound 

system to broadcast recorded Gull-billed Tern 

colony vocalizations were placed on the raft. No 

Gull-billed Terns nested on the raft in 2005 but at 

least five pairs nested on the raft in 2006, although 

no nests successfully hatched (C. C. Schoneman, 

pers. comm.). Gull-billed Tern fledglings and 

parents also used the raft late in the season for 

loafing and roosting. Successful nesting by Gullbilled Terns occurred in 2007 with approximately 

30 nests established on the raft (KCM). In 2006, 

a second and larger nesting platform, also using 

decoys and recordings, was constructed on stilts 

in the Salton Sea (M. A. Ricca, pers. comm.). This 

platform was not used by Gull-billed Terns but was 

colonized by four pairs of nesting Black Skimmers. 

In 2007, a maximum of 28 Gull-billed Tern nests 

were observed on the platform, with minimal nest 

and fledgling success (KCM). Ramps were installed 

on the raft and elevated plaforms to assist chicks 

to nest sites if they fell from or left the site before 

fully fledging off. Strong winds and waves damaged 

the integrity of ramps at both sites, requiring 

modification and annual maintenance 

(C. C. Schoneman, pers. comm.). Although the 

value of artificial nesting platforms is unclear, 

their potential benefit of providing nesting habitat 

free from human disturbance and mammalian 

predators merits further study (C. C. Schoneman, 

pers. comm.).

Education

Apart from signs at various colony sites and 

interpretive information provided at some federal 

and state wildlife refuges, there is little or no 

outreach specifically relating to Gull-billed Terns. 

On the east coast, the Virginia Coastal Bird 

Partnership, a program involving agencies, research 

institutions, and conservation organizations, 

was formed in 1993 to monitor waterbirds and 

educate the public about them; Gull-billed Terns 

have been a specific focus of this group (RME). 

In southern California, Gull-billed Terns have 

received a negative public perception because of 

their observed predation on two species listed under 

the ESA (KCM). Discussions with managers of 

the listed species’ habitats are needed to develop 

management actions benefiting all three species.
Conservation Recommendations 19

(2) Minimize disturbance to nesting colonies by 

conducting surveys outside the colony, wherever 

possible, using observers in blinds or vehicles or 

observing from a distance to prevent flushing.

(3) Count fledging and near-fledging age young 

approximately three weeks after the first chick has 

hatched on the colony to measure breeding success.

(4) Explore the potential for conducting surveys 

of Gull-billed Terns in the species’ winter range 

from the Gulf of Mexico coast states south 

through Mexico, Central America, the Caribbean, 

and northern South America to determine winter 

distribution and the overlap in wintering by 

both G. n. aranea and G. n. vanrossemi and to 

aid in determining conservation needs on the 

wintering grounds.

(5) Use field identification cards of Gull-billed Terns 

to train surveyors to identify both breeding and 

wintering terns and to estimate the approximate 

age of pre-fledged young.

Habitat Management and Protection

Protection of nesting and foraging habitat of Gullbilled Terns is vital to the long-term survival of the 

species. Conservation programs aimed at reducing 

or reversing the impacts of river channelization, 

changes in sediment deposition, beach erosion, 

sea level increases, regional water transfers, and 

other landscape level perturbations will ensure 

the long-term viability of Gull-billed Tern habitat. 

Because most Gull-billed Terns spend their annual 

cycle in the United States and either Mexico, 

Central America, or the Caribbean, conservation 

efforts will require multi-national cooperation. 

Laws protecting habitat range-wide and prohibiting 

take in countries outside the United States require 

better enforcement. Increased international 

communication and cooperation between biologists 

may help refine conservation strategies.

(1) Evaluate active and historic colony sites to 

identify opportunities to enhance or protect 

colonies. Develop and implement colony specific 

management plans to improve colony security and 

reproductive success and to reduce threats.

Our recommendations for range-wide 

conservation practices for both G. n. aranea and 

G. n. vanrossemi emphasize monitoring, habitat 

management and protection, and research. 

These recommendations are in priority order 

within each section.

Monitoring

(1) Conduct breeding population surveys focused 

specifically on Gull-billed Terns. Small colony size 

and unique nest sites, substrates, and seasonality 

may cause colonies to be overlooked during multispecies surveys and aerial waterbird surveys may 

fail to distinguish Gull-billed Tern nests from those 

of other terns.

(a) Standardize survey methodology recognizing 

that it may need to be modified for location, size, 

distribution, and habitat of an individual colony.

(b) Report abundance in number of pairs 

whenever possible, so that data are comparable 

across regions. Measure “number of adults” 

rather than “number of nest attempts” 

given the species’ low nest site tenacity and 

re-nesting ability.

(c) Coordinate the seasonal timing of Gull-billed 

Tern surveys within regions.

(d) Conduct range-wide surveys every three 

to five years as Gull-billed Tern populations 

may fluctuate inter-annually and site fidelity 

is relatively low. More frequent surveys (i.e., 

annually) for the subspecies G. n. vanrossemi

are recommended.

(e) On state, federal, and other managed 

conservation lands, survey Gull-billed Tern 

colony sites annually for presence (or absence) of 

nesting birds. If the colony consists only of Gullbilled Terns, conduct a single survey to coincide 

with the peak incubation period. If other species 

are present, conduct a visit timed specifically for 

Gull-billed Terns.

(f) Conduct baseline surveys along the Gulf 

of Mexico Coast in Mexico to determine 

breeding distribution, colony status, and 

abundance of G. n. aranea. Once this has 

been determined, conduct periodic surveys 

as described in (d), above.

Conservation Recommendations
20 Status Review and Conservation Recommendations for the Gull-billed Tern

(5) Develop population viability models for Gullbilled and California Least terns and western 

Snowy Plovers to assess each species’ population 

health and to evaluate the effects of Gull-billed Tern 

predation.

(6) Conduct long-term studies to determine age and 

sex-specific mortality, fecundity rates, and lifetime 

reproductive success for both subspecies.

(7) Investigate specific foraging patterns of 

Gull-billed Tern adults.

(8) Investigate winter distribution and ecology of 

colonies breeding in the United States and Mexico 

through banding, auxiliary marking, and telemetry.

(9) In conjunction with surveys in Mexico and 

Central America, take measurements and collect 

specimens or tissues of breeding birds to delineate 

the southern limits of the breeding ranges of both 

G. n. aranea and G. n. vanrossemi and to determine 

the subspecific identity of breeding birds in 

Central America.

(10) Investigate contaminants in Gull-billed Terns 

that may result from foraging in agricultural areas.

(11) Investigate the value of artificial nesting 

platforms.

(12) Determine nest success of roof-nesting 

Gull-billed Tern populations to determine 

the importance of this substrate to breeding 

populations.

(13) Gather information on lethal control of 

G. n. vanrossemi at shrimp farms in western 

Mexico to determine effects to the subspecies’ 

population.

Conclusion

The current population of the subspecies G. n. 

aranea in the United States is estimated to be 

approximately 3610 pairs, with over 60% occurring 

in Texas. This species is possibly extirpated in 

Maryland and Delaware. The number of pairs has 

declined in Virginia, North Carolina, Florida, and 

possibly Georgia, but appears stable in Texas. The 

subspecies G. n. vanrossemi has 737 to 808 breeding 

pairs in western Mexico and California. Trend 

information for G. n. vanrossemi is unavailable 

because of the lack of data from Mexico prior to 

2003. The main causes of population declines in 

North America are disturbance of nesting colonies, 

loss of natural nesting islands, and development or 

modification of upland foraging habitats.

(a) Reduce erosion of nesting islands by 

supplementing with crushed shell, gravel, or sand 

(0.2-0.4 mm) and/or installing riprap borders 

where necessary and feasible.

(b) Manage vegetation growth to heights of less 

than 12 cm and densities of less than 14% cover, 

as indicated by Parnell et al. (1995), to provide 

suitable open space for Gull-billed Tern colonies.

(c) Assess active colonies to determine the need 

for predator management Design and implement 

an integrated predator management program 

using non-lethal (e.g., fencing) and, where 

necessary, lethal predator control measures in 

coordination with state and federal agencies. 

Implement measures to control feral and 

domestic pets that impact colony nesting success.

(2) Seek long-term protection for all colony sites 

through land acquisition or conservation easements 

or agreements.

(3) Seek long-term protection of upland foraging 

habitats through land acquisition or conservation 

easements or agreements.

(4) In coordination with ESA recovery teams, 

design and implement a multi-species management 

strategy for Gull-billed and California Least terns, 

western Snowy Plovers, and other ground-nesting 

waterbirds in coastal southern California.

(5) Given the importance of the Salton Sea to 

G. n. vanrossemi, ensure that restoration and 

management plans for the Salton Sea address the 

subspecies’ long-term habitat needs.

(6) Reduce or limit lethal control of Gull-billed Terns 

at aquaculture farms in northwestern Mexico.

(7) Provide informational signs and other 

outreach material at colony sites to reduce human 

disturbance.

Research

(1) Develop standardized monitoring and analytical 

protocol for trend analysis in range-wide surveys.

(2) Investigate the subspecies taxonomy of 

Gull-billed Terns.

(3) Develop techniques to identify and establish 

alternative nesting sites in southern California for 

G. n. vanrossemi to decrease conflicts with 

California Least Terns and western Snowy Plovers.

(4) Use video monitoring techniques at co-occurring 

G. n. vanrossemi, California Least Tern, and 

western Snowy Plover nests to evaluate the impacts 

of Gull-billed Tern predation.
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26 Status Review and Conservation Recommendations for the Gull-billed Tern

Research/Monitoring: Research focused on Gullbilled Terns has not been conducted in Alabama. 

Comprehensive surveys were conducted in the state 

in 1976 and 1983. Since 2001, state-wide censuses 

have been conducted annually (R. B. Clay, pers. 

comm.). Field work for a state Breeding Bird Atlas 

is currently underway (R. B. Clay pers. comm.).

Conservation/Management Activities: Dauphin and 

Pelican islands are privately owned, while Gaillard 

Island is an active dredge disposal site owned by 

the state. No conservation or management activities 

specific to nesting waterbirds occur at these sites 

(R. B. Clay, pers. comm.).

State Status: Protected (Alabama Natural Heritage 

Program 2008).

Natural Heritage Rank: S2—Imperiled (NatureServe 

Explorer 2006).

Habitat Conditions: In Alabama, nesting occurs on 

undeveloped, low elevation sandy shoal islands 

sparsely vegetated with dune grasses and on a 

dredged-material island that provides bare nesting 

substrate (R. B. Clay, pers. comm.).

Threats: All three islands are of low relief and 

breeding efforts may be swamped by the surge 

of early season tropical storms and hurricanes 

(R. B. Clay, pers. comm.). Human disturbance 

can be significant on Dauphin and Pelican islands 

(R. B. Clay, pers. comm.).

a See Appendix C for contact information for contributors 

to the state and regional summaries.

UNITED STATES

Alabama

Summary: Imhof (1976) considered Gull-billed 

Terns uncommon summer residents, with breeding 

restricted to islands in the southwestern part of 

the state, in Mobile Bay and the Mississippi Sound 

in Mobile County. They occur more commonly as 

migrants on Alabama’s Gulf of Mexico Coast (> 75 

birds observed on 6 Aug 1960) with small numbers 

wintering in upper Mobile Bay and the Mississippi 

Sound (Imhof 1976). In recent years, small colonies 

of Gull-billed Terns (totaling only a few dozen 

breeding pairs) have been found on Gaillard Island, 

a dredged material island in Mobile Bay, and on two 

natural barrier islands, Dauphin and Pelican islands, 

in the Mississippi Sound (Fig. A-1).

Population Trends: Breeding Gull-billed Terns were 

apparently never abundant in Alabama during the 

1900s. Small numbers of Gull-billed Terns were 

first documented from Petit Bois Island, near 

the Mississippi/Alabama border, on 4 July 1913, 

where only about 15 or 20 pairs were believed to 

be nesting (Howell 1924). Three active nests were 

reported at Cedar Point in 1956 (Imhoff 1976) and 

23 individuals were reported on Dauphin Island 

in 1976 (Portnoy 1977). More recently, as many as 

87 pairs have nested in Alabama (Table A-1; R. B. 

Clay, pers. comm.). Although breeding numbers are 

highly variable, an average of about 50 pairs nested 

annually at one to three colonies from 1988–2004 

(Fig. A-1; Tables 2, A-1).

Appendix A: State and Regional Summaries of 

Gelochilidon nilotica aranea Status Within the 

Breeding Range in the U.S., Mexico, and Caribbeana

Table A-1. Number of Gull-billed Tern breeding pairs at colonies in Mobile County, Alabama, 1988–2004 

(R. B. Clay, pers. comm.). Dash (—) indicates data are insufficient to discern site availability, occupancy, or 

extent of survey coverage for a particular site and year.

Colony 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004

Dauphin I. — — — — — — — — — — — — — 15 0 0 30 

(west end)

Gaillard I. 59 57 72 3 34 90 12 58 39 14 75 10 2 5 0 9 20

Pelican I. — — — — — — — — — — — 35 50 67 50 0 35

Totals 59 57 72 3 34 90 12 58 39 14 75 45 52 87 50 9 70
Appendix A 27

Delaware and Maryland

Summary: Gull-billed Terns have bred sporadically 

and in very small numbers in at least two known 

sites in Delaware. At Rehobeth Bay and Assawoman 

Wildlife Refuge, between 1958 and 1991 (Hess et 

al. 2000). Gull-billed Terns are virtually extirpated 

in Maryland and are considered rare summer 

residents with records primarily from Worcester 

County in the extreme southeastern portion of 

the state. The species has nested at South Point 

dredged-material islands, Clam Harbor Tumps, 

Oyster Island, Big Bay Marsh, and Ocean City 

spoil, all in Worcester County (Brinker 1996). The 

numbers of breeding pairs in Maryland peaked in 

the 1950s and 1960s, and since 1986, the state has 

seen intermittent breeding by only a single pair. 

Unsuitability of sand and shell dredged-material 

due to island erosion or vegetation succession 

has been a factor in the virtual extirpation of this 

species from Maryland.

Population Trends: Breeding in Delaware was first 

documented in 1958, when three clutches were 

collected at Rehobeth Bay (Hess et al. 2000). 

Gull-billed Terns possibly bred at Assawoman 

Figure A-1. Locations and sizes of Gull-billed Tern colonies in Alabama, 2004.

Wildlife Area in 1958; breeding was documented 

there in 1959 and in 1989–1991. No breeding was 

documented from 1983–1987 and there has been no 

documented nesting since 1991 (Hess et al. 2000).

Gull-billed Terns were never numerous historically 

in Maryland (Brinker 1996). The species colonized 

the South Point dredged-material islands in 1945 

and continued to breed there until the early 1960s. 

During the 1950s, 25 to 30 pairs were recorded but 

the number of breeding pairs was considerably 

lower than that in most years. During the 1970s, the 

maximum number of breeding pairs was three and 

the species ceased to breed in the state from 1977–

1983. From 1985–1988, nine, 33, one, and zero pairs 

nested, respectively, and were limited to a single site 

in any one year (Brinker 1996). The location of the 

last confirmed breeding was Big Bay Marsh, where 

possibly one pair has bred intermittently from 

2000–2004 (D. F. Brinker, pers. comm.).

Research /Monitoring: Breeding Bird Atlas field work 

was conducted from 1983–1987 in Delaware (Hess et 

al. 2000) and Maryland (Brinker 1996). Census and 

monitoring efforts in Delaware are unknown but are 

conducted irregularly in Maryland.
28 Status Review and Conservation Recommendations for the Gull-billed Tern

Presently, most nesting occurs in the St. John’s 

River estuary in Duval County and in Tampa Bay 

(Fig. A-2). Most Gull-billed Terns depart Florida 

for the winter, but small numbers remain on 

the Atlantic coast north to Jacksonville and on the 

Gulf coast north to the Tampa Bay area (Stevenson 

and Anderson 1994).

Population Trends: No comprehensive survey data 

are available for the state but a strong downward 

trend is evident. Ogden (1975) reported a total of 

534 pairs nesting near Merritt Island in Brevard 

County and the St. John’s River estuary in Duval 

County in 1975. In 1976 and 1977, census estimates 

from only one or the other of these two Atlantic 

coast sites were available, obscuring any indication 

of trend. Gull-billed Terns were not reported during 

a study of 40 select dredged-material islands in 1977 

(Schreiber and Schreiber 1978). In Franklin County, 

Smith et al. (1993) reported two to three nests on 

the St. George Island causeway from 1990–1992. 

By 2000, populations declined from 1970’s levels 

(to as low as 17 pairs) at the larger Atlantic coast 

colonies (Merritt and Bird islands, Tables 2, A-2).

Research/Monitoring: No research studies specific 

to Gull-billed Terns have been conducted. A 

Breeding Bird Atlas conducted from 1986–1991 

confirmed Gull-billed Terns in only 10 of the state’s 

1028 quadrangles, indicating they are rare and 

extremely localized breeders in Florida (Florida 

Fish and Wildlife Conservation Commission 2003). 

Local coastal censuses were conducted in 1975, 

1980–1985, and in 2000. A comprehensive state-wide 

census for this species has not been undertaken.

Conservation/Management Activities: One of the two 

largest historic colonies where Gull-billed Terns 

were known to have nested within Merritt Island 

NWR and is protected from private development. 

There is no active management specifically directed 

at Gull-billed Terns.

State Status: No status

Natural Heritage Rank: S2—Imperiled (NatureServe 

Explorer 2006).

Habitat Conditions: In Florida, Gull-billed Terns 

nest on coastal beaches, natural estuarine islands, 

coastal marshes, dredged-material islands, islands 

in freshwater lakes, and sand fill at phosphate 

mining areas. Nesting substrates are sandy and 

sparsely vegetated. Gull-billed Terns forage in 

coastal and freshwater marshes, open uplands, 

shrub-dominated fields, and along coastal beaches 

(Smith and Gore 1996).

Threats: Loss, modification, and degradation of 

coastal habitats, including human disturbance, 

flooding, and succession of vegetation at colony sites 

are thought to be significant threats to the species 

(Smith and Gore 1996).

Conservation /Management Activities: No active 

conservation or management measures are 

currently conducted.

State Status: None in Delaware; Endangered in 

Maryland (Maryland Department of Natural 

Resources 2007).

Natural Heritage Rank: SHB, S2N—Possibly 

extirpated in Delaware; S1—Critically Imperiled in 

Maryland (NatureServe Explorer 2006).

Habitat Conditions: In Delaware, breeding habitat 

consisted of salt marshes from Indian River Inlet 

north to Bombay Hook NWR. In Maryland, nesting 

was on dredged-material islands in barren areas of 

sand and shell. The South Point dredged-material 

islands in Maryland became unsuitable due to 

vegetation succession by the early 1960s, and Clam 

Harbor Tumps and Oyster Island have eroded 

to below mean sea level (Brinker 1996). Big Bay 

Marsh, Maryland, is a narrow (2–3 m) shell beach 

of such low elevation that it hardly extends above 

wind-driven storm tides. In Maryland, Gull-billed 

Terns foraged in open salt marshes, fields and along 

beaches (Brinker 1996).

Threats: None described in Delaware. In Maryland, 

succession of vegetation on some dredged-material 

islands is believed to render them unsuitable for 

nesting (Brinker 1996). The limited number of 

available nesting sites in reasonable proximity to 

feeding areas and the loss of two previously used 

nesting islands due to erosion are believed to have 

contributed to their apparent extirpation from the 

state (Brinker 1996).

Florida

Summary: Florida’s Breeding Bird Atlas (Florida 

Fish and Wildlife Commission 2003) considers 

Gull-billed Terns to be rare and highly localized 

breeders in the state. Breeding populations in Duval 

and Brevard counties totaled several hundred pairs 

in the mid-1970s, but overall numbers of birds as 

well as occupied colony sites have since declined, 

likely a result of modification and degradation of 

coastal habitats. The first Florida nest was recorded 

in 1932 at Pensacola in Escambia County (Weston 

1933); however, an egg set collected in 1892 from 

Anna Maria Island in Manatee County predates 

the Pensacola nest. Except for a colony in the 

interior of Palm Beach County and on islands in 

Lake Okeechobee, nesting by Gull-billed Terns has 

been restricted to the northern half of the state. 

Gull-billed Terns have nested in Duval and Brevard 

counties on the Atlantic Coast, in Bay and Franklin 

counties in the Panhandle, in the Tampa Bay area 

in Pinellas and Hillsborough counties (Florida 

Fish and Wildlife Conservation Commission 2003), 

and inland, at the phosphate mines of Polk and 

Hillsborough counties (Smith and Gore 1996). 
Appendix A 29

Table A-2. Number of breeding pairs of Gull-billed Terns at colonies in Florida 1973–1977, 1979, 1985, 

1995, 1998–2000a. Dash (—) indicates data are insufficient to discern site availability, occupancy, or extent 

of survey coverage for a particular site and year. Data from Clapp et al. 1983, Florida Fish and Wildlife 

Commission 2003, Loftin and Sutton 1979, Ogden 1974, 1975, 1979, Portnoy et al. 1981, Smith and 

Alvear 1997. 

Colony 1973 1974 1975 1976 1977 1979 1985 1995 1998 1999 2000

Duval Co.

Bird Islands — 325 249 121 180 0 0 0 0 0 0

Huguenot Memorial Park — — — — — — — 25 0 0 10

Mayport Naval Station — — — — — 67 0 0 0 0 0

Third Bird Island — — — — — — — — — 2 0

Brevard Co. 

Merritt Island NWR 171 89 285 0 150 0 13 0 0 0 0

Franklin Co. 

Apalachicola, Bird Island — — — — — — — — 17 18 6

Hillsborough Co. 

TPA Island 3D — — — — — — — — 1 0 1

Totals 171 414 534 121 330 67 13 25 18 20 17

Figure A-2. Locations and sizes of Gull-billed Tern colonies in Florida, 2000.
30 Status Review and Conservation Recommendations for the Gull-billed Tern

Georgia

Summary: Breeding populations of Gull-billed Terns 

in Georgia have historically been small. In recent 

years only a single island, Little Egg Island Bar, a 

small, wind-swept and wave-washed sand bar at the 

mouth of the Altahama River (Kale et al. 1965), has 

been occupied; about 50 to 100 pairs nest annually 

on this state-owned island (Clapp et al. 1983). 

Ericksen (1926) described the first breeding record 

of four Gull-billed Tern nests on Oysterbed Island in 

1926. Gull-billed Terns nested formerly at the mouth 

of the Savannah River in Chatham County. Burleigh 

(1958) considered the species to be a scarce summer 

resident on the coast of Georgia.

Population Trends: Little quantitative data are 

available for Gull-billed Terns in Georgia prior to 

the 1990s. During the 1990s, fewer than 100 pairs 

nested at Little Egg Island Bar (Fig. A-3; 

Tables 2, A-3). The 2003 census count of 54 pairs at 

this site may indicate a recent decline (Tables 2, A-3; 

B. Winn, pers. comm.).

Table A-3. Numbers of breeding pairs of Gull-billed 

Terns in McIntosh County, Georgia 1993, 1995, 1999 

and 2003 (B. Winn, pers. comm.).

Colony 1993 1995 1999 2003

 Little Egg Island Bar 65 80 50 54

Research/Monitoring: No research studies specific 

to Gull-billed Terns have been conducted. 

Comprehensive surveys were not conducted prior to 

1993. Since then waterbird colony censuses 

have been conducted every two to four years 

(B. Winn, per. comm.).

Conservation/Management Activities: Only one site, 

Little Egg Island Bar, is presently active and 

occurs within a state Protected Natural Area. 

Management activities at this site include the 

posting of protective signage to prevent public 

access year round (B. Winn, pers. comm.). Georgia 

recently completed its comprehensive plan for the 

conservation of wildlife and identified the Gull-billed 

Tern as a high priority species (Georgia Department 

of Natural Resources 2005).

State Status: Threatened (Georgia Department of 

Natural Resources 2005).

Natural Heritage Rank: S1—Critically imperiled 

(NatureServe Explorer 2006).

Habitat Conditions: Given the relatively large tidal 

fluctuations characteristic of Georgia’s coast, the 

extent of suitable nesting habitat for terns; open 

and sandy islands, is highly dynamic and often 

ephemeral in nature (Georgia Department of 

Natural Resources 2005).

Threats: Accelerated urban growth and development 

and parallel increases in levels of disturbance 

by recreationists are believed to be the largest 

threat to colonial breeding birds in the state (B. 

Winn, pers. comm.). Predation of eggs and chicks 

by Laughing Gulls may limit Gull-billed Tern 

reproductive success (B. Winn, pers. comm.).

Figure A-3.

Locations 

and sizes 

of Gullbilled Tern 

colonies in 

Georgia, 

2003.
Appendix A 31

Research/Monitoring: Few studies specifically 

directed toward Gull-billed Terns have been 

undertaken in Louisiana. Leberg et al. (1995) 

examined colony site use by seabirds on dredgedmaterial islands and Mallach and Leberg (1999) 

examined nest site selection and success among 

breeding tern and skimmer colonies in the 

Atchafalaya Delta. Pius and Leberg (1997, 2002) 

examined aggression and nest spacing in 

Gull-billed Tern and Black Skimmer colonies 

and the influence of Gull-billed Terns on nest site 

choice by Black Skimmers.

Colonial waterbird monitoring in Louisiana 

has been conducted irregularly in the past. 

Comprehensive surveys were conducted in 1976, 

1978, 1983, 1990, and 1993–1999. Beginning in 2001, 

comprehensive surveys have been conducted every 

four years (P. L. Leberg, pers. comm.). Coastal 

surveys are conducted aerially, either by helicopter 

or fixed wing aircraft. Rooftop colonies, which may 

contain up to 100 to 200 pairs (R. D. Purrington, 

pers. comm.), are generally not included in coastal 

survey efforts (P. L. Leberg and T. C. Michot, 

pers. comm.); surveys of these colonies are 

conducted opportunistically.

Conservation/Management Activities: All recent 

colony sites occur on state lands and are protected 

from development.

State Status: Rare Animal of Conservation 

Concern (Louisiana Department of Wildlife and 

Fisheries 2008).

Natural Heritage Rank: S2—Imperiled (NatureServe 

Explorer 2006).

Habitat Conditions: In Louisiana, Gull-billed Terns 

nest primarily on barrier beaches, saltmarsh 

shell berms, and dredged-material islands, and 

are almost always in close association with Black 

Skimmers (Portnoy 1977). Dredged-material 

islands that receive regular seasonal deposits of 

dredged-material were thought to be increasingly 

important to nesting Gull-billed Terns and other 

species (Leberg et al. 1995). Islands in inland lakes 

and artificial substrates, such as gravel rooftops, 

are used infrequently. Gull-billed Terns forage over 

coastal marshes, canals, ponds, and lakes (Lowery 

1974, R. D. Purrington, pers. comm.).

Threats: Inundation of estuarine and barrier islands 

by high or storm tides and loss of nesting habitat as 

a result of vegetation succession adversely impact 

nesting success. Human disturbance is believed 

responsible for the premature desertion of rooftop 

colonies in 2004 (R. D. Purrington, pers. comm.).

Louisiana

Summary: Lowery (1974) considered Gull-billed 

Terns to be fairly common permanent residents in 

Louisiana; least numerous in summer, and almost 

strictly coastal in occurrence. Although Gull-billed 

Terns are observed in winter in the rice prairie 

region of Acadia Parish, generally within 30 miles 

of the coast (W. J. Vermillion, pers. comm.), there 

is a record farther inland (> 50 miles of the coast) 

of five individuals over lakes on the Louisiana State 

University campus in Baton Rouge in September 

1965 during Hurricane Betsy (Lowery 1974). 

Portnoy (1977) considered Gull-billed Terns to be 

uncommon breeders in Louisiana. The species 

breeds very locally along the Gulf of Mexico Coast in 

the Atchafalaya Delta in St. Mary and Terrebonne 

parishes, and east to islands in Breton and 

Chandeleur sounds in Plaquemines and St. Bernard 

parishes. A few Gull-billed Terns are reported to 

have bred near Sabine Lake at the Louisiana-Texas 

border (Portnoy 1977) and at Fearman Lake (Martin 

and Lester 1990). Purrington (2001, 2002) reported 

recent breeding attempts from the rooftops of 

several buildings in downtown New Orleans, though 

success in such colonies is generally low. Most of 

the recent colonies occur on the central coast, near 

Marsh Island and Atchafalaya Bay (Fig. A-4; Michot 

et al. 2004, P. L. Leberg, pers. comm.).

Population Trends: No comprehensive census data 

are available for the state prior to 1976; however, 

Louisiana’s small Gull-billed Tern population 

appears to have been relatively stable since the 

1990s. Historical records summarized by Portnoy 

(1977) suggested that Gull-billed Terns had been 

nesting in very small numbers in the Mississippi 

River Delta since 1837 and on the western coast 

since 1906. During the 1960s and early 1970s, up to 

11 nests and 27 birds were documented from Grassy 

Island and the Chandeleur Islands, respectively, in 

St. Bernard Parish (Portnoy 1977). During the first 

comprehensive survey of the eastern Gulf of Mexico 

Coast in 1976, Portnoy (1977) reported 154 pairs 

(or incubating birds, each assumed to represent 

an active nest and thus a pair) in four colonies in 

Louisiana (Table 2), although Clapp et al. (1983) felt 

Portnoy may have overlooked some nesting areas. 

Martin and Lester (1990) reported 161 pairs among 

three colonies during their coastal aerial census in 

1990. Results of annual aerial surveys conducted by 

Linscombe and Vermillion (W. J. Vermillon, pers. 

comm.) from 1991–1999 ranged from 30 to 1120 

incubating adults (Tables 2, A-4). In a survey of 

dredged-material islands in the Atchafalaya Delta 

Wildlife Management Area, Leberg et al. (1995) 

estimated a maximum of 300 to 400 pairs from 

1992–1995. Although this survey involved only 

the central portion of the coast, it is felt to have 

encompassed most of the known sites. 440 pairs 

were reported in a 2001 coastal census 

(Table A-4; T. C. Michot, pers. comm.).
32 Status Review and Conservation Recommendations for the Gull-billed Tern

Table A-4. Number of breeding pairs of Gull-billed Terns at colonies along the coast of Louisiana, 

1976, 1990–1999 and 2001. Dash (—) indicates data are insufficient to discern site availability, occupancy, 

or extent of survey coverage for a particular site and year. Topographic quad names follow the Louisiana 

Natural Heritage Program (LNHP) colony identification numbers. Data from Martin and Lester 1990, 

Michot et al. 2004, Portnoy 1977, G. D. Lester, pers. comm.

Colony 1976 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2001

Iberia Parish 

LNHP 439-Bayou Lucien — — — — — 10 100 40 10 50 100 150

Plaquemines Parish 

LNHP 040-Black Bay South — 0 0 0 0 0 0 0 0 0 0 20

LNHP 082-Grand Gosier I. — 0 0 0 0 0 0 0 20 0 0 0

LNHP 083-Grand Gosier I. — 8 0 0 0 0 0 0 0 0 0 0

LNHP 176-Stake Is. — 0 0 0 0 0 0 100 30 0 0 0

LNHP 361-South Pass — — 0 0 0 40 0 0 0 0 0 0

LNHP 393-South Pass — — 0 0 0 0 0 3 20 100 100 0

LNHP 469-South Pass — — 0 0 0 0 0 0 10 0 0 0

LNHP 524-Taylor Pass — — 0 0 0 0 0 0 0 420 0 0

LNHP 545-Taylor Pass — — 0 0 0 0 0 0 0 0 20 0

LNHP 546-Taylor Pass — — 0 0 0 0 0 0 0 0 20 0

Colony #603037 6 — — — — — — — — — — —

Terrebonne Parish 

LNHP 055-Cat I. Pass — 0 0 0 0 0 0 0 10 0 0 0

LNHP 059-Central Isles 

Dernieres — 0 0 0 0 0 0 0 60 50 0 0

LNHP 161-Point Au Fer — 0 0 0 0 0 0 0 60 0 0 0

LNHP 263-Point Au Fer NE — 150 0 0 0 0 0 0 0 0 0 0

LNHP 440-Jacko Bay — — — — — — — — — — — 145

LNHP 555-Oyster Bayou — — 0 0 0 0 0 0 20 0 0 0

LNHP 556-Central Isles 

Dernieres — — 0 0 0 0 0 0 6 0 0 0

St. Bernard Parish 

LNHP 181-Three Mile Bay 0 0 0 0 0 0 0 0 2 0 0 0

Colony #590008 20 — — — — — — — — — — —

St. Mary Parish 

LNHP 266-Point Au Fer NE — 0 0 0 50 0 0 0 0 0 0 0

LNHP 357-Point Au Fer NE — — 0 0 0 100 100 0 0 0 0 0

LNHP 460-Point Au Fer NE — — 0 300 200 0 0 0 0 0 0 0

LNHP 461-Point Au Fer NE — — 0 0 400 0 0 0 0 0 0 0

LNHP 462-Point Au Fer NE — — 0 0 0 140 200 0 0 500 350 125

LNHP 493-Point Au Fer NE — — 30 50 0 0 0 0 0 0 0 0

LNHP 494-Point Au Fer NE — — 0 0 0 0 0 30 0 0 0 0

Colony #602007 16 — — — — — — — — — — —

Colony #602008 112 — — — — — — — — — — —

Vermilion Parish 

LNHP 060-Fearman Lake — 3 0 0 0 0 0 0 0 0 0 0

Totals 154 161 30 350 650 290 400 173 248 1120 590 440
Appendix A 33

Figure A-4. Locations and sizes of Gull-billed Tern colonies in Louisiana, 2001.

Figure A-5. Locations and sizes of Gull-billed Tern colonies in Mississippi, 2003.
34 Status Review and Conservation Recommendations for the Gull-billed Tern

Mississippi

Summary: Mississippi has a limited shoreline and 

holds only a few dozen pairs of breeding Gull-billed 

Terns. Turcotte and Watts (1999) considered Gullbilled Terns to be uncommon summer residents 

breeding on islands off the Mississippi coast. 

Burleigh (1945) reported them as present and 

nesting on Petit Bois Island in 1913. The first state 

specimens of this species from Horn Island were 

not secured until 1941 (Gandy and Turcotte 1970). 

On the Mississippi mainland, breeding was first 

suspected in June 1955, but not confirmed until May 

1960 at Bayou Casotte in Jackson County. Since this 

record, Gull-billed Terns have nested on various 

dredged-material islands in the Mississippi Sound 

and Pascagoula River channel (Turcotte and Watts 

1999). There is one inland record of a single bird 

feeding over flooded fields in Lowndes County in 

July (Turcotte and Watts 1999). The most important 

recently occupied colony sites are on three barrier 

or dredged-material islands, East Horn, Round, and 

Sand islands, in marshes along large river channels 

(Fig. A-5).

Population Trends: Gull-billed Terns were not 

historically abundant in Mississippi. Up to three 

pairs were believed to be nesting in 1960. In 1962, 

11 pairs were nesting near Pascagoula, while an 

undetermined number of pairs were also present on 

Grand Island in the Mississippi Sound (Gandy and 

Turcotte 1970). Clapp and Buckley’s (1984) report 

of 62 pairs nesting in 1983 conflicts with reports by 

Turcotte and Watts (1999) and Jackson (1983) of 

“as many as 31 nests on dredged-material” in the 

Pascagoula River for that year; perhaps Clapp and 

Buckley (1984) confused the total number of adults 

with the number of nests. A maximum of 150 pairs 

bred at one site in 2004 (Tables 2, A-5); however, two 

to five pairs per site is more typical.

Research/Monitoring: No research studies specific 

to Gull-billed Terns have been conducted in 

Mississippi. Since 1994, Gull-billed Terns have been 

surveyed annually during general waterbird colony 

surveys. Efforts are currently underway to produce 

a Breeding Bird Atlas for the state (M. A. Goodman, 

pers. comm.).

Conservation/Management Activities: East Horn 

and Sand islands fall under the jurisdiction of the 

National Park Service, while the Round Island 

colony occurs on state-owned lands which provide 

relative protection from private development. 

Access to Sand Island is restricted during the 

nesting season, reducing disturbance to breeding 

birds. No other conservation or management 

activities specific to nesting waterbirds occur at 

these sites.

State Status: Species of Greatest Conservation Need 

(Mississippi Department of Wildlife, Fisheries and 

Parks 2005).

Natural Heritage Rank: S2—Imperiled (NatureServe 

Explorer 2006).

Habitat Conditions: In Mississippi, Gull-billed Terns 

nest on dredged-material islands in marshes of 

large river channels and on barrier islands. Nesting 

substrates include beach dunes and bare dredgedmaterial. Gull-billed Terns often nests with other 

terns and Black Skimmers. In Mississippi, Gullbilled Terns feed over open areas such as airports, 

marshes, and beaches (Turcotte and Watts 1999).

Threats: Unknown. Vegetation succession on 

dredged-material islands may limit nesting habitat 

availability. Conflicts with the timing of deposition 

of new dredged-material may interfere with 

colony establishment or adversely affect 

established colonies, as was documented for 

Least, Royal (Thalasseus maximus) and Sandwich 

(T. sandvicensis) terns and potentially Gull-billed 

Terns on an unnamed dredged-material island near 

Horn and Petit Bois islands in Mississippi Sound 

(Jackson 1983).

Table A-5. Number of Gull-billed Tern breeding pairs at colonies in Jackson County, Mississippi, 1988–2004 

(M. P. Stevens, pers. comm.). Dash (—) indicates data are insufficient to discern site availability, occupancy, 

or extent of survey coverage for a particular site and year.

Colony 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004

East Horn I. — — — — — — 0 — 0 0 0 0 0 0 0 1 0

Round I. — — — — — — — 0 — 0 0 — 0 0 0 1 0

Sand I. — — — — — — 0 — 2 1 0 — 0 — 5 0 150

Totals — — — — — — 0 0 0 1 0 0 0 0 5 2 150
Appendix A 35

New Jersey and New York

Summary: Small, but increasing numbers of Gullbilled Terns occupy estuarine islands, dunes, and 

shell bars on the New Jersey coast. The species 

is considered an uncommon summer resident in 

New Jersey (Sibley 1993); the highest count in 

recent years was 92 pairs among five colonies 

in 2001 (Table A-6). Nesting occurs from Ocean 

County south to Cape May County, generally 

on or near the Forsythe NWR (Fig. A-6). The 

small and fairly recently established colonies on 

southwestern Long Island, New York, represent the 

northernmost breeding sites of G. n. aranea. Bull 

(1964) considered Gull-billed Terns to be rare and 

irregular fall visitors on the southern coast of 

Long Island. Two pairs of Gull-billed Terns first 

colonized New York at Black Banks Island near 

Jones Beach State Park in Nassau County in 1975 

(Buckley et al. 1975). Currently, a few pairs now 

breed on islands off southwestern Long Island (Fig. 

A-7; Table A-7).

Population Trends: A pair of Gull-billed Terns 

apparently colonized southern New Jersey (at Stone 

Harbor) by 1926 (Sibley 1993). In 1977, 18 to 19 

pairs nested in the state (Erwin 1979). Over the last 

few decades, the species seems to have experienced 

a moderate increase in the number of breeding pairs 

in New Jersey as 92 pairs bred in 2001 (Fig. A-6; 

Tables 2, A-6). Gull-billed Terns colonized New York 

in 1975 and remained at very low numbers through 

the 1990s. A maximum of 11 pairs bred at three 

sites in New York in 2003 (Fig. A-7; Tables 2, A-7).

Research/Monitoring: No research studies specific 

to Gull-billed Terns have been conducted in either 

state. Aerial censuses of breeding larids are 

conducted via helicopter on an irregular basis in 

New Jersey. Since the late 1970s, coastal censuses 

from Point Pleasant south to Cape May, which 

included counts of Gull-billed Terns, have been 

conducted in 1977, 1978, 1979, 1983, 1985, 1989, 

and 1995 and were extended north to Sea Bright in 

2001 and 2004 (C. D. Jenkins, pers. comm.). 

The Long Island Colonial Waterbird Monitoring 

Project conducts annual censuses of terns in the 

Long Island/New York City region of New York 

(M. R. Wasilco, pers. comm.). During these surveys 

all breeding species are tallied, nest contents 

recorded, and nest locations mapped on aerial 

photos or maps of each site, and information on site 

characteristics, ownership, disturbance factors, 

predation levels, and management needs are 

recorded (M. R. Wasilco, pers. comm.)

Table A-6. Number of breeding pairs of Gull-billed 

Terns at colonies in New Jersey, 1977, 1985, 1995, 

and 2001 (Erwin and Korschgen 1979, R. Andrews 

and C. D. Jenkins, pers. comm.). 

Colony 1977 1985 1995 2001

Ocean Co. 

Chadwick Marsh 5 0 0 0

Atlantic Co. 

Elder Island-Brigantine 8 1 2 0

Channel

Main Marsh Thorofare 0 15 4 0

Oceanville 61470 0 0 0 40

Oceanville 62481 0 0 0 13

Oceanville 65520 0 0 0 10

Oceanville 66530 0 0 0 2

Oyster Thorofare 5 0 0 0

Simpkins Thorofare 0 1 12 27

Cape May Co. 

Jarvis Sound-Wildwood Crest 1 0 0 0

Totals 19 17 18 92

Conservation/Management Activities: No active 

conservation or management measures are 

currently conducted. Of the 12 colony sites in New 

Jersey where Gull-billed Terns are known to have 

nested, nearly 70% occur within federal or state 

wildlife management areas and are relatively safe 

from development. All Gull-billed Tern nesting 

sites in New York occur on public lands under 

local jurisdictions with no specific conservation 

or management actions directed toward their 

populations.

State Status: No status in New Jersey or New York.

Natural Heritage Rank: S1 – Critically imperiled in 

both states (NatureServe Explorer 2006).

Habitat Conditions: In both states, Gull-billed Terns 

nest primarily on estuarine islands composed of 

marsh wrack, and occasionally on sand dunes and 

shell bars. In New York, Gull-billed Terns also nest 

on sand and shell substrates on barrier islands and 

on dredged-material islands.

Threats: Sea level rise and potential inundation 

of low-lying colony sites, increases in gull 

populations, and human disturbance on beaches 

may limit reproductive success in New Jersey. 

In New York, reduced suitability of nesting sites 

due to beach development, increased levels of 

human disturbance, and increases in gull breeding 

populations (Buckley and Buckley 1984) 

appear to be the main threats to Gull-billed Terns. 
36 Status Review and Conservation Recommendations for the Gull-billed Tern Table A-7. Number of breeding pairs of Gull-billed Terns at colonies in New York, 1975, 1984–1999, and 2001–2003. Dash (—) indicates data are insufficient to discern site availability, occupancy, or extent of survey coverage for a particular site and year. Data from Buckley et al. 1975, Sommers et al. 1994, 2001, M. R. Wasilco, pers. comm. Colony 1975 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2001 2002 2003 Long Island, Suffolk Co Cedar Beach

— 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

Long Island, Nassau CoCinder Island Group

—

—

— 1 0 1 1 0 0 2 1 1 0 2 4 4 5 4 1 1

Cuba Island Group

—

— 1 1 0 1 1 1 1 1 0 0 0 0 0 1 0 0 1 0

Deep Creek Meadow

—

—

—

—

— 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0

East Channel Island/Garrett Marsh

— 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 8

Gull Island/ Parsonage Isl. Group

—

—

—

—

—

—

—

—

—

— 1 0 0 0 0 0 0 1 0 0

Jones Beach 2 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0Lawrence Marsh

—

—

—

— 1 0 0 0 0 0 0 0 2 0 0 0 0 0 0 0

Long Meadow Island

—

—

—

—

—

—

—

— 1 0 1 0 0 1 0 0 1 0 0 2

Middle Line Island

—

—

—

— 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

Neds Island

— 1 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

Totals 2 3 2 2 2 3 2 1 2 3 3 1 2 3 4 5 6 6 3 11
Appendix A 37

Figure A-6. Locations and sizes of Gull-billed Tern colonies in New Jersey, 2001.

Figure A-7. Locations and sizes of Gull-billed Tern colonies in New York, 2003.
38 Status Review and Conservation Recommendations for the Gull-billed Tern

North Carolina

Summary: In 1909, Pearson et al. (1919) considered 

Gull-billed Terns to be rare breeders in the state. 

The species has become more abundant since then 

and nesting is more widespread (Parnell and Soots 

1979). Gull-billed Terns are primarily summer 

residents and are reported to nest at a number of 

locations along the Atlantic coast of North Carolina 

from Roanoke Sound south to the Cape Fear River 

(Clapp et al. 1983, Parnell and Soots 1979). Although 

the number of breeding pairs has declined from 

1977 levels, it has remained stable, at around 200 to 

250 pairs, over the last decade (Table A-8).

Population Trends: Long-term trends are difficult to 

discern as comprehensive state-wide censuses did 

not begin until the late 1970s. Parnell and Soots 

(1979) reported 621 Gull-billed Tern nests among 

21 colony sites in 1977. Parnell and McCrimmon 

(1984) later reported that the peak number of nests 

(presumed to equal the peak number of pairs) at 

nine colony sites was 268 in 1977 and 223 in 1983. 

The peak number of nests reported by Parnell et al. 

(1995) for 1993 was 155 at 10 colony sites. During 

this later census, the vast majority of nests were on 

Pamlico Sound in Dare, Hyde, and Carteret counties 

(Parnell et al. 1995). In 2001, 258 pairs were found 

breeding among seven colony sites (Fig. A-8; Tables 

2, A-8). Although the state population size is small, 

it appears to have been relatively stable over the 

last two decades. Recent census results indicate a 

reduction in the number of colony sites, with a shift 

in the center of abundance away from the Cape Fear 

River and toward the northeastern portion of the 

state (Fig. A-8).

Research/Monitoring: No research studies specific 

to Gull-billed Terns have been conducted. The 

North Carolina Wildlife Resources Commission 

and cooperators (North Carolina Audubon Society, 

North Carolina Division of Parks and Recreation, 

National Park Service, and USFWS) conduct coastwide surveys of colonial nesting waterbirds every 

two to three years. These are mainly ground-based 

surveys and all breeding species are counted 

(S. E. Cameron, pers. comm.).

Figure A-8. Locations and sizes of Gull-billed Tern colonies in North Carolina, 2001.
Appendix A 39

Table A-8. Number of breeding pairs of Gull-billed Terns at colonies in North Carolina, 1976–1977, 1983–1993, 1995, 1997, 1999, and 2001. Surveys conducted statewide in 1976, 1977, 1985, and 1993 through 2001 were comprehensive. Dash (—) indicates data are insufficient to discern site availability, occupancy, or extent of survey coverage for a particular site and year. Data from Parnell and Soots 1979, Parnell et al. 1995, Portnoy et al. 1981, D. H. Allen, pers. comm. Colony 1976 1977 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1995 1997 1999 2001Currituck CoBrant Island 29 100 64 0 0 0 0 2 0 0 0 0 0 0 0 0 0Dare CoClam Shoal — — — — — — — — — — — — — — — — 24Dot Island 0 36 7 0 6 — — — — — — — — — — — —Hatteras Beach Site 2 0 0 4 0 0 0 0 1 — — — — — — — — —Hatteras Inlet (06-11) 10 — — — — — — — — — — — — — — — —Hatteras Inlet (09-03) 60 — — — — — — — — — — — — — — — —Hatteras Inlet (09-04) 1 — — — — — — — — — — — — — — — —Hatteras Inlet, Northside Beach 0 0 3 16 7 0 0 0 0 0 4 0 0 7 79 0 0Old Dot Island — 8 — — — — — — — — — — — — — — —Old House Channel, Island L — 4 0 0 15 0 0 0 0 0 0 0 0 0 6 0 0Old House Channel, Island MN (06-08) 10 21 0 0 0 0 0 0 0 0 0 0 0 102 0 0 0Oregon Inlet Beach, South — — — — — — — — — — — — — — 27 6 22Oregon Inlet Shoal — — — — — — — — — — — — — — — — 1Oregon Inlet, Island B — 22 — — — — — — — — — — — — — — —Pea Island Beach, Cedar Hammock — — 4 — — — — — — — — — — — — — —Pea Island Beach, Pole Shed — — — — — — — — — — — — — — — — 5Pea Island, South Pond — — — — — — — — — — — — 1 — — — —Roanoke Sound, Island G 8 — — — — — — — — — — — — — — — —Roanoke Sound, Island H — — 29 — — — — — — — — — — — — — —Sand Shoal Island — — — — — — — 47 11 49 100 50 26 — — — —UNI, Old House Channel — 4 — — — — — — — — — — — — — — —UNI, Pea Island, North Pond 1 — — — 13 — — — — — — — — — — — — —UNI, Stumpy Point Bay 32 4 15 — — — — — — — — — — — — — —Unnamed (03-12) 13 — — — — — — — — — — — — — — — —Unnamed (06-07) 5 — — — — — — — — — — — — — — — —Wells Island — — — — — — — — — — — 10 41 0 0 0 0
40 Status Review and Conservation Recommendations for the Gull-billed Tern Table A-8. (cont’d) Colony 1976 1977 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1995 1997 1999 2001 Hyde Co Big Foot Island

—

—

—

—

—

—

—

—

—

—

—

—

— 25 4 —

—

Hog Island Reef 5 —

—

—

—

—

—

—

—

—

—

—

—

—

—

—

—

North Rock Island

—

—

—

—

—

—

— 4 —

—

—

—

—

—

—

—

—

Ocracoke Flats 16

—

—

—

—

—

—

—

—

—

—

—

—

—

—

—

—

Ocracoke Inlet Beach, North 0 27 0 48 146 4 27 0 0 9 0 0 0 15 5 103 108Ocracoke Inlet, Natural Shoal 

—

—

—

—

—

—

—

— 8 —

—

—

—

—

—

—

—

Shell Castle Island, West

—

—

—

—

—

—

—

—

—

—

—

—

—

— 3 —

—

UNI, Hatteras Ferry Channel 1

—

—

—

—

—

—

—

—

— 2 —

—

—

—

—

—

UNI, Hatteras Ferry Channel 2

— 13

—

—

—

—

—

—

—

—

—

—

—

—

—

—

—

Carteret Co.Beaufort Causeway

—

—

—

—

—

—

—

—

—

— 23

—

—

—

—

—

—

Bogue Sound (22-08) 5 —

—

—

—

—

—

—

—

—

—

—

—

—

—

—

—

Bogue Sound (22-40) 2 —

—

—

—

—

—

—

—

—

—

—

—

—

—

—

—

Bottle Run Point 12 0 0 0 0 0 0 3 0 0 0 0 19 29 0 0 0Cape Point 0 0 0 32 0 33 11 0 16 23 0 0 11 36 0 0 0Cape Point, South Beach

—

—

—

—

—

—

— 25

—

—

—

—

—

—

—

—

—

Core Banks Beach, North, Drum Inlet 0 2 —

—

—

—

—

—

—

—

—

—

—

—

—

—

—

Core Banks Beach, South, Drum Inlet 0 0 3 0 0 0 0 21 0 0 0 0 0 0 1 0 0Core Banks, Power Squadron Spit

—

—

—

—

—

—

— 4 0 0 0 16

—

—

—

—

—

Drum Inlet, North 0 52

—

—

—

—

—

—

—

—

—

—

—

—

—

—

—

Harbor Island

—

—

—

—

—

—

— 2 25 0 0 0 0 0 0 0 0

Morgan Island

—

— 6 0 0 0 0 10

—

—

—

—

—

—

—

—

—

New Drum Inlet, Shoal

—

—

—

—

—

—

—

—

—

—

—

— 1 28

—

—

—

New Dump Island 39 85 0 0 0 0 0 0 0 0 0 0 0 0 0 20 87Newport River, Annex 1 —

—

—

—

—

—

—

—

—

—

—

—

—

—

—

—

Newstump Point

—

—

—

—

—

—

—

—

—

—

—

— 10

—

—

—

—

Old Dump Island

—

—

—

—

—

—

— 5 1 —

—

—

—

—

—

—

—

Portsmouth Island 41

—

—

—

—

—

—

—

—

—

—

—

—

—

—

—

—

Sand Bag Island

—

— 5 0 0 0 0 3 —

—

—

—

—

—

—

—

—

Shackleford Point

—

—

—

—

—

—

—

—

—

—

—

— 37

—

—

—

—

Shell Island 0 1 0 0 0 0 0 16 0 0 0 0 2 0 0 0 0Swash Inlet, Beach

— 15 0 0 0 0 0 0 0 0 0 0 0 2 1 0 0
Appendix A 41

Table A-8. (cont’d)Colony 1976 1977 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1995 1997 1999 2001Tump Island

—

—

—

—

—

—

—

—

— 2 0 0 0 0 0 0 11

UNI, Adjacent Lighthouse Bay (17-03) 9 2 —

—

—

—

—

—

—

—

—

—

—

—

—

—

—

UNI, Back Sound 4

—

—

—

—

—

—

—

—

—

—

—

—

— 4 —

—

—

UNI, Core Sound 3

— 2 —

—

—

—

—

—

—

—

—

—

—

—

—

—

—

UNI, Swansboro 6 (23-10) 2 0 0 0 0 0 0 2 —

—

—

—

—

—

—

—

—

Unnamed (15-09) 13

—

—

—

—

—

—

—

—

—

—

—

—

—

—

—

—

Unnamed (22-02) 19

—

—

—

—

—

—

—

—

—

—

—

—

—

—

—

—

Unnamed (22-04) 1 —

—

—

—

—

—

—

—

—

—

—

—

—

—

—

—

Westend-Bird Shoal (20-03) 21 6 0 0 0 0 0 2 —

—

—

—

—

—

—

—

—

Onslow Co.UNI, New River Channel 3

—

—

—

—

—

—

— 4 —

—

—

—

—

—

—

—

—

Pender CoOld Topsail Inlet, North 4 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0Rich Inlet, Northside

—

—

—

—

—

—

—

— 1 —

—

—

—

—

—

—

—

Unnamed (29-36) 17

—

—

—

—

—

—

—

—

—

—

—

—

—

—

—

—

New Hanover Co.Ferry Slip Island

—

—

—

—

—

—

—

—

—

—

— 5 0 1 0 0 0

Fort Fisher Beach

—

—

—

—

—

—

— 10 6 6 0 0 0 0 0 0 0

Mason Inlet, Northside

—

—

—

—

—

—

—

—

— 9 —

—

—

—

—

—

—

Masonboro Island 7 —

—

—

—

—

—

—

—

—

—

—

—

—

—

—

—

UNI, Cape Fear River (39-33) 32 0 52

—

—

—

—

—

—

—

—

—

—

—

—

—

—

Bird I. 27

—

—

—

—

—

—

—

—

—

—

—

—

—

—

—

—

South Pelican Island 0 34 0 0 0 0 0 0 0 0 0 0 7 0 11 24 0UNI, Anderson Landing

—

— 41

—

—

—

—

—

—

—

—

—

—

—

—

—

—

UNI, Monks Island, Bowen-Point

— 19 0 0 0 0 0 0 0 3 —

—

—

—

—

—

—

UNI, Old Brunswick (39-26) 87 164

—

—

—

—

—

—

—

—

—

—

—

—

—

—

—

Unnamed (39-29) 40

—

—

—

—

—

—

—

—

—

—

—

—

—

—

—

—

Assignation unknown 27

—

—

—

—

—

—

—

—

—

—

—

—

—

—

—

—

Totals 595 621 233 109 174 37 38 161 68 101 129 81 155 249 137 154 258
42 Status Review and Conservation Recommendations for the Gull-billed Tern

South Carolina

Summary: Sprunt and Chamberlain (1949) 

considered Gull-billed Terns to be sparse and 

irregular breeders in South Carolina. The first nests 

of this species were discovered on Cape Island (at 

Cape Romain) in 1929 (Sprunt and Chamberlain 

1949). Gull-billed Terns nest locally along the 

central coast from Cape Romain and Bull’s Bay 

south to the Savannah River with most nesting 

occurring presently in the Cape Romain area.

Population Trends: Although figures in published 

reports sometimes conflict, state numbers appear 

to be relatively stable over the last 30 years (Tables 

2, A-9). Blus and Stafford (1980) reported an annual 

maximum of 340 nests from up to 10 colony sites 

during their 1969–1975 study. Clapp et al’s (1983) 

map depiction of 12 breeding birds in 1976 near the 

Savannah River conflicts with Clapp and Buckley’s 

(1984) estimate of 231 pairs in 1976. Gull-billed 

Terns in South Carolina exhibit considerable interannual variation; from 1990–2003 the number of 

pairs ranged from 109 to 414 at four to 10 colony 

sites (Fig. A-9; Tables 2, A-9; J. S. Calver, 

pers. comm.)

Research/Monitoring: No research studies specific to 

Gull-billed Terns have been conducted. Field work 

for a breeding bird atlas was conducted between 

1988 and 1995 but survey coverage for colonial 

breeding waterbirds was inadequate to assess state 

numbers (South Carolina Department of Natural 

Resources 2005). Censuses of all colonial breeding 

waterbirds were conducted annually from about 

1987–2004.

Conservation/Management Activities: Of the 27 sites 

where Gull-billed Terns are known to have nested 

in South Carolina, 12 (54%) occurred on NWRs and 

two (7%) on State Heritage Sites. In 2004, only nine 

nesting islands were active, all of which were located 

in Charleston County on lands administered by 

the NWR system or the state’s Heritage Preserve 

Program. Management activities include the posting 

of protective signage and barriers at 18 sites and 

vegetation removal at three dredged-material sites 

(J. S. Calver, pers. comm.). The Gull-billed Tern is 

a South Carolina Priority Species with the highest 

priority ranking (South Carolina Department of 

Natural Resources 2005).

State Status: Species of Concern (South Carolina 

Department of Natural Resources 2005).

Conservation/Management Activities: At least 19 

(23%) of the 82 locations where Gull-billed Terns 

are known to have bred occur within national parks 

or NWRs and are protected. Protective signage 

restricting public access occurs at Oregon Inlet 

Shoal, administered by the USFWS, and Dot 

Island (S. E. Cameron, pers. comm.). No other 

management activities specifically directed at 

nesting Gull-billed Terns are presently conducted 

at these sites (S. E. Cameron, pers. comm.).

State Status: Threatened (North Carolina Wildlife 

Resources Commission 2005).

Natural Heritage Rank: S3—Vulnerable (NatureServe 

Explorer 2006).

Habitat Conditions: In North Carolina, Gull-billed 

Terns nest primarily on open and bare areas of 

undiked dredged-material and natural estuarine 

islands and on coastal beaches. Nesting substrates 

are most often of mixed sand and shell (Parnell et 

al. 1995).

Threats: Flooding of low elevation sites is prevalent 

and occurs at Big Foot Island, Core Banks Beach, 

Ft. Fisher Beach, Harbor Island, Mason Inlet, 

Ocracoke Inlet Beach and Shoal, New Drum Inlet, 

Oregon Inlet Beach and Shoal, and Shell, South 

Pelican, Tump, and Wells islands. Vegetation 

succession on dredged-material islands limit nesting 

habitat. Human disturbances on the outer beaches 

can severely disrupt nesting colonies (North 

Carolina Wildlife Resources Commission 2005).
Appendix A 43

Table A-9. Number of breeding pairs of Gull-billed Terns at colonies in South Carolina, 1975–1976, 1979, 1986–1990, and 1992–2003 (Portnoy et al. 1981, T. M. Murphy, pers. comm.). Statewide census effort begins about 1987; earliest censuses may not have been comprehensive. Dash (—) indicates data are insufficient to discern site availability, occupancy, or extent of survey coverage for a particular site and year.Colony 1975 1976 1979 1986 1987 1988 1989 1990 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003Georgetown Co.Magnolia Beach — 1 — — — — — — — — — — — — — — — — — —North Is., n. end — — — — 6 4 — — — — — — — — — — — — — —Charleston Co.Bird Key, Bull Bay 7 133 0 0 0 28 35 0 0 0 0 0 0 0 0 0 0 0 0 0Bird Key, Stono River — — 56 30 65 7 0 113 0 0 29 0 0 0 0 0 0 0 0 0Cape Is., n. end of n. end — — — — — — — — — — 9 0 0 0 7 0 0 4 0 1Cape Is., n. end of s. end — — — — — — — — — — 0 0 0 0 0 0 0 0 2 0Cape Is., s. end of s. end — — — — — — — — — — 0 1 0 0 0 0 0 0 0 0Cape Island — — 5 8 6 3 5 45 0 0 0 0 0 0 0 0 0 0 0 0Castle Pickney — — — — — — — — — — 2 0 0 6 0 0 0 10 32 0Crab Bank — — — — — 29 79 63 0 16 0 6 76 68 88 26 0 28 0 47Deveaux Bank — — — — 23 85 193 10 53 129 61 7 5 11 15 20 64 27 0 48Kiawah Is., n. end — — — — — — — — — — — 4 — — — — — — — —Lighthouse Isl. — — — 7 17 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0Lighthouse Isl., s. end — — — — — — — — — — 4 1 88 37 2 6 1 5 3 16Marsh Island — — 47 0 38 19 0 0 0 2 10 0 9 0 0 0 12 — — —Raccoon Key — — — — 26 47 15 8 44 0 31 84 0 0 58 0 15 0 8 0Raccoon Key, Sandy Pt. — — — — — — — — — 87 0 0 0 13 5 0 0 24 0 21Skimmer Flats 26 30 2 6 0 9 0 3 0 167 36 21 0 0 0 0White Banks (all isls. combined) 46 12 — — — — — — — — — — — — — — — — — —White Banks, east 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 27 0White Banks, middle 0 0 0 0 0 0 0 27 40 59 14 25 6 24 0 52 0 0White Banks, west 0 0 15 0 30 18 0 0 0 0 0 22 0 2 0 21 26 0Beaufort Co.Egg Bank Isl. — — — 4 0 0 0 14 — — — — — — — — — — — —Joiner Bank — — — — — 2 21 136 0 7 — — — — — — — — — —Jasper Co.Savannah River NWR — 8 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0Savannah Spoil, Site 12B — — — — — — — — — — — — — — — 0 0 0 0 28Savannah Spoil, Site 14B e. — — — — — — — — — — — — — — — 20 164 204 0 78Savannah Spoil, Site 14B w. — — — — — — — — — — — — — — — 0 0 0 11 0Totals 53 154 108 49 222 254 380 414 97 277 186 165 192 349 218 119 256 375 109 239
44 Status Review and Conservation Recommendations for the Gull-billed Tern

Figure A-9. Locations and sizes of Gull-billed Tern colonies in South Carolina, 2003.

Natural Heritage Rank: SNR—Unranked 

(NatureServe Explorer 2006).

Habitat Conditions: Gull-billed Terns in South Carolina 

nest primarily on natural estuarine and barrier 

islands and on dredged-material islands. Nesting 

substrates used are primarily sand and shell.

Threats: Presently, breeding Gull-billed Terns in 

South Carolina may be limited by the availability 

of suitable nesting locations as the more southerly 

sites used previously in St. Helena Sound and 

Port Royal have been lost as a result of erosion 

(South Carolina Department of Natural Resources 

2005). Tidal inundation of the remaining low-lying 

colony sites, mammalian predation, and human 

disturbances adversely affect reproductive success 

in these colonies (J. S. Calver, pers. comm.).
Appendix A 45

Texas

Summary: The coast of Texas appears to be the 

core area of abundance for G. n. aranea, and the 

state’s breeding population, estimated at over 2000 

pairs in recent years, is the highest of any state 

in the United States or Mexico. Texas colonies 

have accounted for over 60% of the United States 

population of G. n. aranea during the current 

decade. Oberholser (1974) considered Gull-billed 

Terns to be fairly common residents along the Texas 

coast, nesting locally, but with fewer birds present 

in winter. Lockwood and Freeman (2004) indicate 

that this species is common along the coast, though 

much less numerous in winter. Pemberton (1922) 

described nesting colonies of Gull-billed Terns near 

Port Isabel in Cameron County, where he found 

them to be abundant, possibly ranging into the 

“many thousands.” Since the mid-1990s, colonies 

containing several hundred nests have formed 

annually at two inland saline lakes, La Sal Vieja 

and East Lake, in Willacy County (W. H. Howe 

and D. Blankinship, pers. comm.). Small resident 

populations are established farther inland at Falcon 

Reservoir in Zapata County, and Lake Casa Blanca 

in Webb County (Lockwood and Freeman 2004).

Figure A-10. Locations and sizes of Gull-billed Tern colonies in the upper coast of Texas, 2003.

There are three centers of breeding abundance 

along the coast (Figs. A-10 through A-12; 

Tables A-10 through A-12): (1) the upper coast, 

encompassing Sabine Lake, Galveston Bay, and 

the Brazoria County Wetlands; (2) the central 

coast encompassing Lavaca, Matagorda, Aransas, 

Nueces, San Antonio, and Corpus Christi bays; and 

(3) the lower coast encompassing the Upper and 

Lower Laguna Madre. Many of the largest and 

most consistently occupied colony sites are found 

in the central and lower coasts (Texas Colonial 

Waterbird Society 1982) including 12 of the 14 

colony sites that contained an annual median of 

> 51 pairs. The lower, central, and upper coasts 

contain 38%, 35%, and 27% of all colony sites used 

in the state, respectively. Consistency of site use 

was greatest for the lower coast where 38% of 52 

sites were used for 15 or more years over the 31 

year period. Site use consistency was lower on 

the central coast (17% of 48 sites), and lowest on 

the upper coast (3% of 38 sites). From 1990–2003, 

the three largest coastal colonies occurred most 

consistently at Mustang Bayou Island in Galveston 

Bay and Laguna Vista and Green Hill Spoil Island 

in Lower Laguna Madre. The median numbers of 

pairs at these sites were 375, 110, and 100 pairs, 

respectively. In comparison, the median for all 78 

sites occupied in any year was 20 pairs. The median 

colony size rather than the mean is given due to the 

large annual variation among sites.
46 Status Review and Conservation Recommendations for the Gull-billed Tern Table A-10. Number of breeding pairs of Gull-billed Terns at colonies along the upper coast of Texas, 1988–2003 (U.S. Fish and Wildlife Service 2004). Dash (—) indicates data are insufficient to discern site availability, occupancy, or extent of survey coverage for a particular site and year. Colony 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 Sabine Lake; Jefferson Co. Motiva Headquarters

—

— 0 0 0 0 0 0 0 0 0 6 8 0 0 0

Galveston Bay; Chambers Co.Atkinson Island 0 0 0 0 0 0 0 0 0 0 0 0 0 0 64 6Galveston Bay; Harris Co.St. Mary’s Island

—

—

—

—

—

—

—

—

—

—

—

—

—

— 27 28

Galveston Bay; Galveston Co.Bay Harbor Bar 0 0 0 0 0 3 0 0 0 0 1 0 0 0 0 4Carancahua Cove Terraces 0 0 0 0 0 0 0 0 0 0 0 0 37 34 2 0Eckert Bayou Point

—

—

—

—

—

—

— 0 15 0 22 0 0 0 0 0

Gangs Bayou 0 0 0 0 5 3 0 0 0 0 0 0 0 0 0 1HGNC Evia Island

—

—

—

—

—

—

—

—

—

—

—

—

— 50 0 23

Jig Saw Island 0 0 0 0 0 0 0 0 2 0 0 0 0 0 0 0Jumbilee Cove/Live Oak Grove

—

—

—

—

—

— 8 0 0 0 0 0 0 0 12 9

Little Pelican Island 0 0 0 0 6 0 15 0 0 0 0 0 0 15 0 0Magnolia Compress #4 40 15 0 0 0 0 0 0 0 0 0 0 0 0 0 0Marker 52 Spoil Island 0 0 0 0 0 0 0 0 5 0 0 0 0 0 0 0McAllis Point 0 0 0 0 40 4 0 0 0 0 0 0 0 0 0 0Mensell Bayou Point 0 0 45 0 0 0 1 2 0 0 0 0 0 0 0 0Moody Compress 

—

—

—

—

—

—

—

—

— 26 10 15 0 7 13 0

Pelican Island 56 43 85 25 15 0 0 0 0 0 0 0 0 0 0 0San Luis Pass 0 6 0 0 0 0 2 0 0 0 3 3 2 0 0 0Smith Point Island 0 0 0 0 0 0 0 0 10 0 10 0 0 0 0 0Snake Cove Point 0 0 0 0 0 0 15 0 0 0 0 0 0 0 0 0Snake Island 0 0 0 9 0 0 0 0 0 0 0 0 0 0 0 0Swan Lake 0 0 0 0 0 16 0 0 0 15 20 50 8 15 0 9West Bay Mooring Facility

—

—

—

—

—

—

—

—

—

—

—

—

—

— 6 0
Appendix A 47

Table A-10. (cont’d)Colony 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003Galveston Bay; Brazoria Co.Arcadia Reef 0 0 0 0 0 0 0 0 0 4 0 0 0 0 0 0Bastrop Bay 0 20 0 0 0 5 0 0 5 0 0 0 0 0 10 0Drum Bay 2 3 0 0 0 0 0 0 0 0 0 0 0 0 0 0Freeport Dow 0 0 0 0 0 0 10 0 20 30 0 130 60 72 60 0Mustang Bayou Island (PA 67) 0 0 0 30 35 0 1420 1400 24 10 1400 0 1200 375 1100 200San Luis Island 0 0 0 0 0 0 0 4 0 0 0 0 0 0 0 0Brazoria Co. Wetlands; Brazoria Co.Cedar Lakes 25 10 0 0 0 0 0 0 0 0 0 0 0 0 0 0Wolf Lake Skimmer Area

—

—

—

—

— 15 0 15 23 24 46 100 0 0 65 0

Matagorda Bay; Matagorda Co.Dressing Point 0 0 25 0 0 0 0 0 0 2 0 0 0 0 0 0Sundown Island 0 4 10 0 0 0 30 0 0 3 5 8 15 0 0 12Matagorda Bay; Cahoun Co.Matagorda Bay Spoil 39-51 3 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0Matagorda Wtlds; Matagorda Co.STP Cooling Reservoir

—

—

—

—

—

— 905 0 0 0 0 0 650 744 424 184

Victoria Co. Wetlands; Victoria Co.Gravel Pits

—

—

—

—

— 15 0 0 0 0 0 0 0 0 0 0

Lavaca Bay; Calhoun Co.Lavaca Bay Spoil (51-63) 7 0 0 0 25 0 0 0 30 25 0 10 0 0 0 0Lavaca Bay Spoil (63-77) 10 0 0 15 0 0 60 0 85 0 0 0 0 0 0 0Mouth of Chocolate Bayou 0 10 60 67 11 0 75 0 30 90 0 2 75 8 48 35Mouth of Lavaca River 10 0 0 20 40 0 0 0 0 0 0 0 0 40 3 0Point Comfort Alcoa 25 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0Totals 178 111 225 166 177 61 2541 1421 249 229 1517 324 2055 1360 1834 511
48 Status Review and Conservation Recommendations for the Gull-billed Tern

Figure A-11. Locations and sizes of Gull-billed Tern colonies in the central coast of Texas, 2003.

Population Trends: Although the number of pairs of 

Gull-billed Terns breeding along the Texas coast 

varies among sites from year to year, the overall 

number of nesting birds in Texas appears to have 

been generally stable from 1973–2003. An analysis 

of decadal abundance reveals a median number of 

1632 pairs during the 1970s, 1936 pairs during the 

1980s, 1565 pairs during the 1990s, and 2203 pairs 

during the 2000s (Tables A-10 through A-12). The 

median number of colony sites that were occupied 

during each of those decades is 27, 39, 36, and 38, 

respectively.

Research/Monitoring: Chaney et al. (1978) studied 

nest success of Gull-billed Terns on dredgedmaterial islands. Newstead and Blacklock (2005) 

observed kleptoparasitic behavior of Gull-billed 

Terns on Black Skimmers and Forster’s Terns in 

Nueces Bay in 2004. Comprehensive waterbird 

colony surveys along the coast have been conducted 

annually by the Texas Colonial Waterbird Census 

Project since at least the early 1970s. Censuses of 

two sites at inland salt lakes in Willacy County have 

been conducted annually by NWR personnel since 

about 1995 (D. Blankinship, pers. comm.).

Conservation/Management Activities: Most colony 

sites are located on state or private lands, with 

a majority leased and managed by Audubon 

Texas. A few colonies occur on NWR lands or on 

lands owned by the National Audubon Society. 

Management activities at sites in the central 

coast area include controlling human disturbance, 

removal of mammalian predators, treatment of fire 

ants, vegetation removal, and invasive grass control. 

Pilot studies experimenting with substrate addition 

(e.g., oyster shell and dredge shell hash) have 

been implemented by the Coastal Bend Bays and 

Estuaries Program (D. J. Newstead, pers. comm.). 

Fencing (conventional or electric) has been used 

at two NWR colony sites, the Wolf Lake Skimmer 

Area at the Brazoria NWR and East Lake at the 

Lower Rio Grande Valley NWR, to prevent access 

of mammalian predators to nesting sites (D. S. 

Stolley, pers. comm.). In recent years, there have 

been efforts to re-flood the Bahia Grande, resulting 

in the creation of isolated islands that historically 

have been used by nesting Gull-billed Terns 

(D. J. Newstead, pers. comm.).

State Status: No status.

Natural Heritage Rank: S4—Apparently Secure 

(NatureServe Explorer 2006).
Appendix A 49

Table A-11. Number of breeding pairs of Gull-billed Terns at colonies along the central coast of Texas, 1988–2003 (U.S. Fish and Wildlife Service 2004). Dash (—) indicates data are insufficient to discern site availability, occupancy, or extent of survey coverage for a particular site and year.Colony 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003San Antonio Bay; Calhoun Co.Cedar Lake Island — — — — — — — — — 0 18 48 0 0 0 0Seadrift Island 0 0 0 0 0 8 0 0 35 107 9 0 0 7 2 0Steamboat Island and Spoil 34 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0Aransas Bay; Aransas Co.Blackjack Point Reef 0 0 0 0 0 0 0 0 0 8 0 0 15 13 0 0Cedar Bayou 0 0 0 0 0 0 0 0 0 0 2 0 0 0 0 0Little Bay 0 0 0 0 0 0 0 0 0 650 0 135 0 0 0 0Long Reef-Deadman Isls. 80 13 15 0 0 0 0 0 0 0 7 0 0 0 0 60Matagorda Spit 0 0 0 0 0 0 0 0 0 0 0 0 3 0 0 0Second Chain of Isls. 30 138 40 0 0 2 14 0 55 41 15 0 65 42 58 15Third Chain of Isls. 6 54 150 0 0 35 14 0 0 34 0 0 16 18 0 0Aransas Bay; Nueces Co. Bay Harbor — — — — — — 0 0 0 0 1 0 0 0 0 0Causeway Island Platforms 21 10 18 0 0 0 0 0 0 2 2 0 0 0 0 0Danger Island 3 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0East Shore Spoil 0 0 0 0 2 0 0 0 0 0 16 24 0 0 25 0GIWW Marker 53 Spoil 10 — — — — — — — — — — — — — — —GIWW Marker 55-57 Spoil 3 — — — — — — — — — — — — — — —West Harbor Island 0 56 0 0 0 0 0 0 0 0 0 0 0 0 0 0Corpus Christi Bay; Nueces Co.CC Channel Spoil 0 0 0 0 0 0 6 0 0 0 0 0 8 8 0 0East Nueces Bay 0 5 2 0 0 0 0 0 0 30 0 1 0 0 0 0Ingleside Point 0 0 0 0 0 14 0 0 0 3 0 5 0 0 0 2Oso Bay — — — — — — — — — — — — 20 — — —Pelican Island Spoil 30 21 5 0 0 12 6 4 5 0 0 8 3 3 0 74Shamrock Island 0 0 0 0 0 0 0 3 11 10 18 0 7 7 0 0Skimmer Island — — — — — — — — — — — — — — 120 0Sunset Lake 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0West Nueces Bay 0 20 14 0 36 3 2 22 0 14 21 31 100 78 0 190
50 Status Review and Conservation Recommendations for the Gull-billed Tern Table A-11. (cont’d) Colony 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 Upper Laguna Madre; Nueces Co. Causeway Islands 0 0 0 0 0 0 11 1 0 0 0 0 0 3 0 0 Kennedy Causeway Isls. 30 12 92 40 32 18 18 26 56 49 71 62 39 34 43 0 Naval Air Station Islands 0 0 1 0 8 58 46 41 4 2 30 0 35 21 20 0 Pita Island/Humble Channel 2 8 47 74 6 30 24 14 0 4 14 11 20 0 0 3 Upper Laguna Madre; Kleberg Co. Chaney Island

—

—

—

—

—

—

—

—

—

—

—

—

—

— 18 70

Diked Island NM 178 6 2 20 0 0 0 0 0 0 0 0 0 0 0 0 0DM31-34 (NM65-74) 0 0 0 0 15 0 0 0 8 7 0 0 0 0 10 14Marker 3 -38 Spoil NM 79 19 2 10 0 2 0 18 5 8 7 0 0 0 0 0 0Marker 63-65 Spoil (NM 127-131) 3 24 8 26 104 43 21 10 15 4 15 0 3 6 14 13Marker 69 Spoil (NM 141) 0 14 0 8 18 43 36 0 30 77 21 20 0 21 6 0Marker 72 Spoil Island (NM 152) 42 24 12 72 2 58 28 0 0 11 18 9 0 15 13 26Marker 77A Spoil Island (NM 155) 7 18 52 0 0 13 4 0 8 0 0 0 0 0 0 0Marker 81 Spoil Island (NM 163) 0 12 30 0 0 0 0 0 0 68 5 0 3 0 0 8Marker 85 A Spoil Island (NM 165) 59 8 50 0 10 30 35 0 0 4 42 24 1 41 0 0Marker 91 Spoil Island 0 8 2 1 14 42 12 6 14 97 18 6 1 7 0 0North Bird Island 0 0 0 0 0 0 8 0 16 0 0 0 0 0 0 0North of Bird Island Marker 43 0 46 1 0 14 32 10 3 0 13 22 4 17 7 13 0Side Channel Island (NM 199) 0 0 0 44 0 0 2 0 0 0 8 21 0 0 0 0South Bird Island 0 0 30 0 0 14 1 32 0 21 0 0 0 0 0 11South of South Bird Island 38 0 10 2 0 0 1 21 0 0 2 13 0 0 0 0West of North Bird Island 0 0 0 0 0 8 0 0 0 0 0 0 0 0 0 0Yellow House Spoil (NM 162)

—

—

—

—

—

—

—

— 24 0 0 0 0 0 0 0

Upper Laguna Madre; Kenedy Co.Marker 139-155 Spoil (19-35) 61 70 210 0 74 18 0 3 41 25 44 0 42 22 40 36N.Yarborough Pass (NM 37-39) 0 38 6 0 34 44 0 0 0 0 14 0 17 0 0 0S.Yarborough Pass (NM 41-47) 28 2 0 0 6 0 0 0 0 24 0 0 36 29 28 0The Hole 0 0 0 0 6 0 0 0 0 0 0 0 0 0 0 52Yarborough Pass 0 0 0 0 0 0 0 0 28 0 0 0 0 0 0 0Baffin Bay; Kleberg Co.Marker 103-117 Spoil (NM 207-221) 0 0 0 0 16 0 3 7 13 0 34 0 0 21 2 0South Baffin Bay Island 24 36 0 0 28 25 35 42 24 35 32 41 70 35 32 38Totals 536 641 825 267 427 550 355 240 395 1347 499 463 521 439 444 612
Appendix A 51

Habitat Conditions: Gull-billed Terns nest on natural 

estuarine islands, natural shell and sand bars 

and spits, and dredged-material islands along the 

Intracoastal Waterway (Oberholser 1974). They 

occasionally nest on islands or isolated peninsulas 

in large freshwater reservoirs (Lockwood and 

Freeman 2004) or on levees surrounding the cooling 

reservoir of a nuclear power plant (P. Glass, pers. 

comm.). The preferred nesting habitat is sparsely 

vegetated or barren shell beaches of isolated islands 

(Texas Colonial Waterbird Society 1982). The 

species forages over salt and freshwater marshes, 

wet coastal prairies and fields, and along bay shores 

(Oberholser 1974, Lockwood and Freeman 2004).

Threats: Vegetation succession and island erosion 

are threats to nesting habitat (J. K. Wilson and 

P. Glass, pers. comm.). The observed increase in 

the numbers of nesting Laughing Gulls in Corpus 

Christi Bay in their immediate colonization of newly 

constructed nesting islands is a potential threat (D. 

J. Newstead, pers. comm.). Prior to 1986, annual 

counts of Laughing Gulls in Corpus Christi Bay 

ranged between 3000 and 9000 pairs (Texas Colonial 

Waterbird Society 1982). Since 1986, annual counts 

consistently exceeded 10,000 pairs, with high counts 

in some years ranging from 15,000 to nearly 20,000 

pairs.

Figure A-12. Locations and sizes of Gull-billed Tern colonies in the lower coast of Texas, 2003.
52 Status Review and Conservation Recommendations for the Gull-billed Tern Table A-12. Number of breeding pairs of Gull-billed Terns at colonies along the lower coast of Texas, 1988–2003 (U.S. Fish and Wildlife Service 2004, D. S. Stolley, pers. comm.). Dash (—) indicates data are insufficient to discern site availability, occupancy, or extent of survey coverage for a particular site and year. Colony 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 Laguna Madre; Kenedy Co. East Flats Spoil 0 0 0 0 0 0 0 0 0 0 0 0 0 0 2 14 South Land Cut 130 85 259 185 175 22 256 99 29 0 8 0 10 17 13 0 Laguna Madre; Willacy Co. Green Hill Spoil Island 14 38 441 117 170 100 63 108 16 0 4 0 0 0 15 0 Green Island Spoils 81 1 83 22 3 0 0 20 15 0 166 0 47 0 61 0 Mansfield Channel Spoil 0 0 0 0 0 0 0 0 0 0 0 0 0 6 0 0 NE Mansfield Int 0 0 0 30 0 40 0 15 60 0 15 0 11 17 6 0 SW Mansfield Int 2 0 2 1 —

—

—

—

—

—

—

—

—

—

—

—

Laguna Madre; Cameron Co.Arroyo Colorado Spoil 0 110 472 0 210 370 76 150 20 0 69 8 23 0 3 5Dead Pecker Hill 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0East Arroyo Spoil 0 0 0 0 120 0 0 0 0 0 0 0 25 0 0 0Four Islands 0 0 0 0 0 0 10 0 10

—

—

—

—

—

—

—

Green Island 0 18 10 0 0 0 0 0 0 0 0 0 4 0 0 0Green Island Reef NW 85 0Laguna Vista Spoil 259 100 382 110 60 300 300 400 70 0 0 9 45 0 54 150Port Isabel Spoil 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0South Three Islands 0 0 60 15 7 0 20 50 0 0 0 0 33 0 30 0Three Island Spoil 43 45 109 0 23 110 85 50 50 0 15 42 17 0 18 0“Salt Lakes” tracts; Willacy Co.La Sal Vieja

—

—

—

—

—

—

—

—

—

—

—

—

—

— 154–171 >127

East Lake

—

—

—

—

—

—

—

—

—

—

—

—

—

— 0 135–175

Totals 529 398 1818 480 768 942 810 892 270 0 277 59 215 41 441–458 331–371
Appendix A 53

Conservation/Management Activities: Of the 

47 sites where Gull-billed Terns are known to 

have bred, the two (4%) occurring on NWRs and 

17 (36%) occurring on lands owned by The Nature 

Conservancy are protected. Predator control 

(primarily of mammals) occurs at six of these sites: 

Assateague South, Assawoman Island, Fisherman 

Island, Middle Metomkin Island, North Metomkin 

Island and Parrymore Island. Protective signage 

and/or barriers restricting public entry to colonies 

currently occur at 13 sites: Assateague South, 

Cedar Island, Cobb Island, Fisherman Island, Hog 

Island, South, Middle and North Metomkin islands, 

Myrtle Island, Parrymore Island, Ship Shoal Island, 

Smith Island, and Wreck Island.

State Status: Threatened (Terwilliger and Tate 1995).

Natural Heritage Rank: S2—Imperiled (NatureServe 

Explorer 2006).

Habitat Conditions: In Virginia, Gull-billed Terns 

nest on estuarine islands composed of shell or 

marsh-wrack, on barrier islands composed of sand 

and shell with sparse vegetation, and, rarely, on 

man-made features such as at the Hampton Roads 

Bridge Tunnel (RME). They nest primarily with 

Common Terns and Black Skimmers.

Threats: In Virginia, flooding is a primary cause 

of nest failure at marsh island sites (Rounds et al. 

2004). These low elevation islands are frequently 

subjected to complete inundation from spring 

high tides as well as during storm surges. Erwin 

et al. (2006) documented that marsh build up in 

Virginia has not kept pace with local sea level rises, 

thereby limiting the quantity of suitable breeding 

habitat. Predation by mammals, gulls, and Great 

Horned Owls are primary causes of colony failure 

on barrier islands (Erwin et al. 2001, O’Connell and 

Beck 2003). The loss of 77% of 133 eggs from 64 

nests in 1990 and 1991 was attributed to Herring, 

Great Black-backed, or Laughing gulls (O’Connell 

and Beck 2003). Eyler et al. (1999) reported that 

predation by Great Horned Owls on large chicks 

was a major factor in the low reproductive success 

of Gull-billed Terns (0.53 chicks per nest) in 

1994–1996. Dramatic changes in the distribution of 

raccoons and red foxes on Virginia’s barrier islands 

between 1977 and 1998 coincided with significant 

declines in the number of Gull-billed Terns and 

other breeding larids, suggesting that mammalian 

predation may be a major factor in the colony site 

selection and success of Gull-billed Terns and other 

breeding birds (Erwin et al. 2001).

Virginia

Summary: Breeding Gull-billed Terns were 

considered common on the Virginia coast by 1890 

(Bailey 1913). Virginia was a stronghold for this 

species at least through the mid-1970s, but strong 

declines have been noted since then, possibly 

due to a combination of colony site flooding and 

mammalian predation. Despite this decline, Virginia 

colonies of Gull-billed Terns remain numerically 

important and the best-studied within the 

range of G. n. aranea and are among the better 

known for the species as a whole. Gull-billed Terns 

have nested on the Atlantic side of the lower 

Delmarva Peninsula in Accomack and Northampton 

counties from the vicinity of Chincoteague south to 

the islands near Cape Charles. An additional site 

exists on an artificial island within the Hampton 

Roads Bridge Tunnel complex in the urban 

Hampton-Norfolk area.

Population Trends: The number of Gull-billed Terns 

in Virginia has exhibited a strong downward 

trend since the 1970s. About 2000 pairs nested in 

Virginia in 1975–1976 and fewer than 1000 pairs 

nested in 1980 and 1982 (Buckley and Buckley 1984, 

Spendelow and Patton 1988). Gull-billed Terns 

continued to decline to only about 290 pairs at 

16 sites in 2003 (Fig. A-13; Tables 2, A-13). The 

105 breeding pairs at two colony sites reported 

for 1977 by Erwin (1979) and Erwin and Korschgen 

(1979) appears to severely underestimate the true 

number (Spendelow and Patton 1988) and probably 

reflects only part of the breeding population in 

that year.

Research/Monitoring: Erwin et al. (1998a and 1998b) 

examined colony site dynamics and diet during 

the breeding season. Eyler et al. (1999) examined 

hatching success and chick growth. O’Connell and 

Beck (2003) examined the impacts of gull predation 

on the reproductive success of Least, Gull-billed, 

and Common terns and Black Skimmers. Gull-billed 

Tern colonies are monitored annually as part of the 

Virginia Coastal Bird Partnership (RME).
54 Status Review and Conservation Recommendations for the Gull-billed Tern

Table A-13. Number of breeding pairs of Gull-billed Terns at colonies in Virginia, 1975–1977, 1984, and 

1993–2003 (Williams et al. 1990, R. Andrews, B. R. Truitt and B. D. Watts, pers. comm.). Comprehensive 

surveys conducted statewide in 1977, 1984, 1998, and 2003.

Colony 1975 1976 1977 1984 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003

Delmarva Peninsula; Accomack/Northampton Co.

Assawoman Island 0 0 1 0 3 0 3 3 0 0 0 0 0 0 0

Big Easter 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0

Brant Hill 0 0 0 0 15 15 13 8 0 0 0 0 0 0 0

Cedar Creek-Eckichy 0 0 0 0 0 0 0 25 86 34 58 22 8 4 0

Cedar Island 3 7 1 0 17 61 127 110 20 10 0 23 3 37 16

Chimney Pole Marsh 0 8 0 0 0 25 0 0 0 0 0 0 0 0 0

Chincoteague Chn-No. 0 0 0 0 0 10 0 10 0 0 0 0 0 0 0

Chincoteague-Willis 0 0 0 0 3 0 0 0 0 0 0 0 0 0 0

Chinccoteague-Wire Narrows 0 0 0 0 5 8 0 0 0 0 14 12 46 38 32

Coards Marsh, Chincoteague 0 0 0 6 0 20 0 5 0 0 0 0 0 0 0

Cobb Island 29 32 67 10 0 0 0 12 0 0 0 0 0 0 0

Conjer-N/L. Sloop 0 0 0 0 3 0 20 26 14 0 0 20 12 0 30

Conjer-So. 0 0 0 0 3 0 15 8 3 0 6 0 2 0 20

Dawson Shoals 5 0 19 18 0 0 0 0 0 0 0 0 0 0 0

Egg Marsh, Chincoteague 0 0 0 0 0 0 0 0 22 38 29 47 27 1 13

Egging Marsh 0 0 0 0 8 0 25 8 6 0 0 23 0 0 3

Fisherman Island 0 0 7 0 0 0 0 0 0 0 0 0 0 0 0

Gap Marsh, Quinby 0 0 0 0 0 0 0 0 0 63 40 27 95 35 101

Great Channel 0 0 0 0 0 0 0 0 0 0 0 0 0 0 4

Gull Marsh 0 0 0 12 0 0 0 0 0 0 0 0 0 0 0

Hodges Narrows 0 0 0 0 5 0 0 0 0 0 2 1 0 5 2

Hog Island 81 53 107 50 0 0 3 0 0 0 0 0 0 0 0

Hummock Creek-Wach 0 0 0 0 0 50 51 15 0 1 9 0 2 7 0

L. Cobb 200 41 0 0 15 3 33 1 1 0 1 0 4 0 0

L. Easter 0 0 0 0 13 0 50 0 5 7 0 3 0 0 0

Man and Boy 0 0 0 0 0 0 0 0 0 11 0 12 37 4 5

Middle Metomkin Island 0 0 0 0 55 21 0 0 0 3 0 0 0 0 0

Middle Mouth Creek 0 0 0 4 0 0 0 0 0 0 0 0 0 0 0

Myrtle Island 197 87 31 8 0 0 3 0 0 0 0 1 0 0 0

N. Metomkin Island 0 0 0 40 10 0 0 0 0 0 0 0 0 0 0

Oyster Thoro-Channel 0 0 0 0 0 0 0 10 17 13 6 0 0 0 25

Parramore Island 11 19 3 0 0 0 0 0 0 0 0 0 0 0 0

Pelican 0 0 0 0 0 0 0 0 15 0 0 0 0 0 0

Point of Marsh 0 0 0 0 0 0 0 0 17 43 0 0 0 0 1

Queen Sd. Channel. 0 0 0 0 0 0 0 0 0 0 0 0 0 0 5

Bridge. Chinc.

Running Channel 0 0 0 0 0 0 6 0 30 0 12 0 0 0 0

Ship Shoal 367 53 67 65 4 0 48 10 25 0 0 1 0 0 0

Smith Island, North 104 293 284 60 0 0 0 0 0 0 0 0 0 0 0

S. Clubhouse Point shellpile 0 0 0 0 0 0 0 0 0 0 0 6 0 0 0

S. Metomkin Island 480 707 142 140 0 0 0 0 0 0 0 0 0 0 0

SwashBay 0 0 0 0 0 0 4 12 0 0 0 0 0 0 0

Wach-CM #8 0 0 0 0 0 0 15 20 43 0 0 4 0 0 0

Wach-Black Rock Reach 0 0 0 0 0 0 0 0 0 3 0 0 0 0 4

Wreck Island N. 8 33 0 0 106 74 14 62 5 8 30 0 0 11 14

Wreck Island S. 0 0 0 0 0 0 0 0 0 5 3 25 14 52 0

Chesapeake Bay; Norfolk Co.

Hampton Rds. Bridge Tunnel 0 0 0 0 0 0 0 0 0 61 65 35 11 11 18

Totals 1485 1333 729 413 265 287 430 345 309 301 275 262 261 205 293
Appendix A 55

Chardine et al. (2000) reported Gull-billed Terns 

breeding in Cuba and Hispaniola in the past, but no 

recent data are available. There are four historic 

specimen records from Cuba (in June, July, and 

September from Camaguey, Guantanamo, and Isla 

de la Juventud provinces) and at least one specimen 

record from the Dominican Republic (from Monte 

Christi in August) and four records from the Ouest 

Department of Haiti in May and August (Molina 

and Erwin 2006).

Population Trends: No information is available on 

current population size or trend.

Research/Monitoring: No studies specific to 

Gull-billed Terns have been conducted in the 

Caribbean. No regular monitoring has been or 

is currently being conducted. A comprehensive 

survey covering 42 islands and cays in 2004 and 

2005 documented a small remnant colony on 

Anegada Island in the British Virgin Islands in 2005 

(McGowan et al. 2006).

Conservation/Management Activities: None known.

Protective Status: No status.

CARIBBEAN

Summary: Norton (1982) reported up to ten 

Gull-billed Terns nesting on Anegada Island 

in the British Virgin Islands. McGowan et al. 

(2006) reported at least four pairs breeding there. 

Chardine et al. (2000) indicated one or two pairs of 

Gull-billed Terns bred in the U. S Virgin Islands, 

but specific locations were not given. There are 11 

historic specimen records of this species in the U.S. 

Virgin Islands; from the islands of St. Croix and St. 

Thomas from May through September, and an egg 

set from Cockroach Cay (Molina and Erwin 2006).

Gull-billed Terns are an uncommon summer visitor 

to the Bahamas, mainly from April through August 

(Raffaele et al. 1998). Sprunt (1984) noted 12 pairs 

on Grand Inaugua in 1967 and 1972. Chardine et al. 

(2000) estimated that the population in the Bahamas 

might be as high as 100 to 300 pairs, but there are 

no specific data that support this estimate. There 

are 15 historic specimen records of Gull-billed Terns 

in the Bahamas spanning the period March through 

August (Molina and Erwin 2006).

Figure A-13. Locations and sizes of Gull-billed Tern colonies in Virginia, 2003.
56 Status Review and Conservation Recommendations for the Gull-billed Tern

Natural Heritage Rank: Unranked.

Habitat Conditions: Gull-billed Terns nest on isolated 

salt ponds on Anegada Island in the British Virgin 

Islands. No other information exists on habitats 

occupied by Gull-billed Terns in the remainder of 

the Caribbean.

Threats: Specific threats to Gull-billed Terns in the 

Caribbean are unknown. Chardine et al. (2000) 

cite egg harvesting and human disturbance as 

the major threats to West Indian breeding larids. 

Sprunt (1984) and Chardine et al. (2000) suggest 

that protection of nesting sites, more effective 

enforcement of protective laws, and public education 

are all needed.

MEXICO

Summary: Gull-billed Tern are an uncommon to 

fairly common local breeder in the Laguna Madre 

in Tamaulipas. The only documented nesting 

in Tamaulipas is reported by Garza-Torres 

and Navarro S. (2003), but the species is found 

throughout the year in the Laguna Madre region 

(Contreras-Balderas 1993). Howell and Webb (1995) 

suggest that the species nests south on the Gulf 

of Mexico coast at least to central Veracruz, but 

no specific sites are mentioned. Areas of greatest 

promise for Gull-billed Terns nesting in Veracruz 

are Laguna Tamiahua on the northern coast, where 

a breeding colony of Black Skimmers has been 

documented, and possibly in Laguna Alvarado on 

the southern coast.

No information is available on the status of Gullbilled Terns in Tabasco or the Yucatan Peninsula 

(including the states of Campeche, Quintana 

Roo, and Yucatan). Historic records in Tabasco 

and Yucatan during the breeding season are rare 

(Molina and Erwin 2006). Howell and Webb (1995) 

map this species as a “winter (non-breeding)” 

visitor in Tabasco and along the entire coast of 

the Yucatan Peninsula. The species is not mentioned 

in coastal breeding waterbird surveys by 

Rangel-Salazar et al. (1993).

Population Trends: No information is available on 

current population size or trends.

Research/Monitoring: In 2005, a survey for Gullbilled Terns was conducted in Laguna Tamiahua 

and Pueblo Viejo in Veracruz resulting in no 

observations (EM, EP). No other research 

studies specific to Gull-billed Terns in eastern 

Mexico and no statewide or regional censuses of 

colonial breeding waterbirds have been conducted. 

Conservation organizations are reportedly in the 

early stages of biological inventory for the coastal 

regions of Veracruz (E. Peresbarbosa pers. comm.).

Conservation/Management Activities: None known.

State Status: No status in any Mexican state.

Natural Heritage Rank: Unranked.

Habitat Conditions: Habitats utilized by Gull-billed 

Terns are poorly known, but presumably include 

sparsely vegetated or barren shell beaches of 

isolated islands. Potential breeding habitats, in the 

form of sandy islands, exist in bays and estuaries 

on the northern and southern coasts of Veracruz. 

In the non-breeding season, Gull-billed Terns are 

presumed to utilize interior wetlands and coastal 

tidal zones (Howell and Webb 1995). Extensive 

areas of non-breeding habitat potentially occur 

along coastal lowlands, particularly in and around 

Laguna Tamiahua and Laguna Alvarado 

in Veracruz.

Threats: Specific threats to Gull-billed Terns are 

unknown. Garza-Torres and Navarro S. (2003) 

reported that most sites suitable for breeding larids 

in the Laguna Madre of Tamaulipas have been 

severely altered by human activities.
Appendix A 57

Chardine, J. W., R. D. Morris, J. F. Parnell, and J. 

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Appendix A 59

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60 Status Review and Conservation Recommendations for the Gull-billed Tern

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Appendix B 61

Appendix B: State Summaries of Gelochelidon nilotica 

vanrossemi Status Within the Breeding Range in the 

U.S., Mexico, and Caribbeana

Gull-billed Terns forage in tidal and agricultural 

habitats throughout much of the Mexicali Valley and 

Colorado River delta. This species is not known to 

occur along the Gulf of California shoreline south of 

San Felipe, nor is it found on the Gulf islands (away 

from the immediate delta). There are a few records 

of transients on the Pacific coast in the vicinity of 

Ensenada (Erickson et al. 2001).

Gull-billed Terns were unknown historically in 

Baja California Sur apart from two specimens 

purportedly taken at Cabo San Lucas in 1859 

but not subsequently located (Grinnell 1928). In 

1996, four pairs of Gull-billed Terns nested at the 

saltworks near Guerrero Negro in the extreme 

northwestern part of the state (Danemann and 

Carmona 2000), and four, 14, and 10 pairs were 

reported nesting there in 2002, 2003, and 2005, 

respectively (Fig. B-1; Tables 3, B-1; Palacios and 

Mellink 2007, EM, EP). Otherwise the species is 

known only as a rare visitor in winter in the El 

Centenario-Chametla area at the south end of Bahia 

de La Paz (Erickson et al. 2003).

Population Trends: No information on trend is 

available for Baja California or Baja California Sur.

a See Appendix C for contact information for contributors 

to the state summaries.

Table B-1. Number of breeding pairs of Gull-billed Terns at colonies in Baja California and Baja California 

Sur, México, 1992–1994, 1996–2005. Dash (—) indicates no survey was conducted; n/a = birds were present 

but not counted. Data from Danemann and Carmona 2000, Molina and Garrett 2001, Palacios and Mellink 

1993, 2007, EM, KCM, EP.

Colony 1992 1993 1994 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005

Baja California-interior

Cerro Prieto geothermal ponds — — — 136 85–100 56 — 140 191 >144 153 234 161

Baja California-Gulf of California

Isla Montague 150–200 92 94 — — 77 77 — — — 30 n/a 113

Baja California Sur

Guerrero Negro saltworks — — — — — — — — — 4 14 — 10

Laguna Ojo de Liebre saltworks — — — 4 — — — — — 0 0 — 0

MEXICO

Baja California and Baja California Sur

Summary: Gull-billed Terns are found very locally in 

Baja California and the only significant populations 

are in the lower Colorado River delta region 

and adjacent agricultural valleys in the extreme 

northeastern portion of the state (Molina and Erwin 

2006). Friedmann et al. (1950) cited possibly the 

first nesting of Gull-billed Terns at Isla Montague 

at the mouth of the Colorado River, based on 

specimens taken there on 16 May 1915. Currently, 

there are two known breeding colonies in Baja 

California; Isla Montague, where the number of 

nesting pairs ranged from 150 to 200 in 1992 to 30 

in 2003 (Palacios and Mellink 1993, EM, EP), and 

Cerro Prieto Geothermal Area (Campo Geotérmico 

Cerro Prieto) in the Mexicali Valley, where 100 

to 234 pairs nested from 1996–2004 (Molina and 

Garrett 2001, KCM). Although the numbers of pairs 

at Isla Montague and Cerro Prieto have remained 

fairly stable in recent years (Fig. B-1; Tables 3, 

B-1), nesting success at Isla Montague appears 

to be low in most years because of tidal flooding 

(Peresbarbosa and Mellink 2001, KCM) while nest 

success at Cerro Prieto is usually high (EM, KCM, 

EP). Complete colony failures were reported at Isla 

Montague in 2004 and 2005 as high tides flooded all 

early nest attempts in both years, with birds failing 

to renest (KCM).
62 Status Review and Conservation Recommendations for the Gull-billed Tern

Research/Monitoring: Since the mid-1990s, censuses 

of breeding colonial waterbirds at both Isla 

Montague and Cerro Prieto have been conducted 

nearly annually, but have varied in methodology 

and intensity. Biologists from the Upper Gulf of 

California and Colorado River Delta Biosphere 

Reserve conduct seasonal monitoring of shorebirds 

at Cerro Prieto, Isla Montague, and surrounding 

areas, and opportunistically collect information on 

the presence and numbers of Gull-billed Terns and 

other colonial waterbirds. Prior to 2003, surveys 

for Gull-billed Terns in Baja California Sur were 

conducted opportunistically as part of other studies.

Conservation/Management Activities: Signage 

indicating the protective status of migratory birds 

has been posted recently at Cerro Prieto. Although 

Cerro Prieto occurs on federal land, administered 

by the Comisión Federal de Electricidad, and 

is located at the northern end of a conservation 

area encompassing the Río Hardy watershed, no 

active habitat management is conducted here. Isla 

Montague is in the Upper Gulf of California and 

Colorado River Delta Biosphere Reserve (a federal 

natural protected area), and though it is not actively 

managed for colonial nesting birds, access and land 

use changes are restricted at the site. Although the 

saltwork colonies in Baja California Sur are in the 

Viscaino Biosphere Reserve, they occur on private 

lands and receive no special management.

Figure B-1. Locations and sizes of Gull-billed Tern colonies in coastal northwest Mexico, 2003.

State Status: No status in either state.

Natural Heritage Rank: Unranked in both states.

Habitat Conditions: The nesting substrate at Isla 

Montague consists of fine sediments with sparse 

salt grass (Distichlis palmeri) and isolated 

mounds of broken clam shells. At Cerro Prieto, 

nesting occurs on earthen islets located within 

waste water impoundments. Foraging habitats 

include the extensive tidal flats of the delta as 

well as river channels, agricultural canals, and 

flooded agricultural fields. The small colonies 

at the Guerrero Negro saltworks occurred on 

sand and shell islands (Danemann and Carmona 

2000, EM, EP).

Threats: Inundation and failure of nests on the 

tidal flats on Isla Montague occurs regularly 

(Peresbarbosa and Mellink 2001, KCM). A potential 

threat to reproduction at Isla Montague and Cerro 

Prieto is predation by mammals, particularly 

coyotes and raccoons. Large variations in the 

water levels of impoundments at Cerro Prieto may 

increase access to nesting islands by mammalian 

predators or may inundate nests. No threats have 

been reported from Baja California Sur sites.
Appendix B 63

The colony at Isla El Rancho contained five, 23, 

five, and 15 pairs in 2000, 2001, 2002, and 2003, 

respectively (Fig. B-2; Tables 3, B-2; X. Vega, 

pers. comm.). In 2005, only 1-2 pairs attempted to 

nest (KCM).

Van Rossem (1945) presumed the Gull-billed Tern 

to be a common breeder near Bahia Tobari in 

Sonora, based on specimens he collected in the area. 

Breeding surveys in 1994 by Palacios and Mellink 

(1995) and focused surveys in 2003 and 2005 failed 

to document nesting colonies in all of coastal Sonora 

(Palacios and Mellink 2007).

This species is a common winter visitor in the 

larger coastal estuaries in Sinaloa and, throughout 

Marismas Nacionales and the San Blas area in 

Nayarit. Non-breeding birds also occur widely in 

small numbers in major estuaries, along the coast, 

and in adjacent agricultural zones in the Colorado 

River delta in Sonora (KCM). The species was 

mapped as a winter visitor along the coast in Colima 

(Howell and Webb 1995), but not found on nonbreeding surveys of Laguna Cuyutlan (Mellink and 

de la Riva 2005).

Population Trends: No information on trends is 

available for any of these states. The only site that 

has been monitored regularly is Isla El Rancho; 

Colima, Nayarit, Sinaloa, and Sonora

Summary: Gull-billed Terns were not mentioned in 

a partial survey of the birds of Colima (Schaldach 

1963). A single colony was found at Laguna 

Cuyutlan southeast of Manzanillo in Colima in 2003 

(EM, EP) and 2005 (Fig. B-2; Tables 3, B-2; Palacios 

and Mellink 2007).

The most thorough work on the avifauna of Nayarit 

(Escalante 1988) did not record Gull-billed Tern 

breeding, but breeders were recently confirmed 

(EM, EP). In 2003, two pairs of Gull-bill Terns 

nested at Estero Teacapan and 120-150 pairs nested 

at Laguna Pericos in Marismas Nacionales (Fig. 

B-2; Tables 3, B-2; Palacios and Mellink 2007). In 

2005, only Laguna Pericos was occupied with 160 

pairs. Thus Laguna Pericos, one of only three colony 

sites in southern west Mexico, supports the largest 

population away from the Colorado River delta.

In Sinaloa, Gull-billed Terns are known only from 

a single colony. Gonzalez-Bernal et al. (2003) 

first documented a small breeding colony on Isla 

El Rancho (approximately 120 ha) in northern 

Bahia Santa Maria in 2000, although a specimen 

in breeding condition was collected in 1934 from 

nearby Isla Laricion (Molina and Erwin 2006). 

Figure B-2. Locations and sizes of Gull-billed Tern colonies in coastal southwest Mexico, 2003.
64 Status Review and Conservation Recommendations for the Gull-billed Tern

the estimated number of breeding pairs has varied 

from one or two to 23 pairs since the colony’s 

discovery in 2000. If a colony did exist early in the 

20th century at Bahia Tobari, Sonora it now appears 

that the species has become extirpated as a breeder 

in the state.

Research/Monitoring: Comprehensive surveys were 

conducted in Colima and Nayarit in 2003 and 2005. 

Breeding Gull-billed Terns have been surveyed 

annually in the Bahia Santa Maria-Ensenada 

Pabellones area in Sinaloa during general waterbird 

colony surveys since 2000. Munoz del Viejo et al. 

(2004) documented the reproductive success of 

seabirds, which included Gull-billed Terns, in Bahia 

Santa Maria. No surveys or research for Gull-billed 

Terns have been conducted in Sonora.

Conservation/Management Activities: No specific 

management actions directed toward nesting 

colonies occur in Colima, Nayarit, and Sonora. 

Although Isla El Rancho lies within the Gulf of 

California Island Park System and is included in 

the Conservation of Critical Coastal Ecosystems in 

Mexico program for Bahia Santa Maria, no specific 

management activities are directed toward the 

nesting colonies. Local educational programs work 

to increase awareness of the wildlife values of the 

bay (X. Vega, pers. comm.). Except for protective 

signage, no special conservation management 

actions have been practiced in Sinaloa.

State Status: No status for all states.

Natural Heritage Rank: Unranked for all states.

Habitat Conditions: In Colima, Gull-billed Terns nest 

on small islets in sandy mudflats with saltmarsh 

vegetation dominated by glasswort (Salicornia sp.) 

and saltwort (Batis maritime; Palacios and Mellink 

2007). Foraging information is not available. In 

Nayarit, Gull-billed Terns nest on sandy barrier 

beaches or sandy islets with some stands of 

mangrove (Palacios and Mellink 2007, EM, EP). 

Foraging Gull-billed Terns concentrate at shrimp 

farm ponds (Palacios and Mellink 2007, EM, EP) 

and at a variety of extensive tidal and seasonally 

inundated flats.

In Sinaloa, nesting occurs on a sandy shoal island 

consisting of periodically tide-washed sand and 

crushed shell flats and sparse, low Salicornia 

plants (EM, EP). In Sinaloa and Sonora, 

Gull-billed Terns forage at commercial shrimp 

ponds and occur widely over extensive tidal flats, 

mangrove estuaries and channels, seasonallyinundated flats, and, in Sonora, along agricultural 

canals and irrigated fields.

Threats: Human disturbance is low at the Laguna 

Cuyutlan colony site as it is accessible only by canoe 

or kayak, however, large scale tourism development 

around Manzanillo could potentially threaten the 

ecological integrity of this site. The nesting colony 

on Isla El Rancho is subject to tidal inundation, 

and the success of Gull-billed Tern colonies there 

has generally been low (X. Vega, pers. comm.). 

Although prohibited by Mexican law, the eggs of 

other waterbird species on Isla El Rancho have 

been collected for local consumption, and the 

chicks of some species have been used as bait in 

crab traps (Gonzalez-Bernal et al. 2003, Munoz del 

Viejo et al. 2004). Disturbance by inappropriately 

timed educational tours has interrupted waterbird 

breeding attempts. Agricultural wastewater 

entering the Bahia Santa Maria system could lead 

to high pesticide and nutrient loads (GonzalezBernal et al. 2003). The Estero Teacapan site in 

Nayarit receives high levels of human disturbance 

from fishing activities.

Gull-billed Terns concentrate at the many 

commercial shrimp ponds in Nayarit, where 

lethal means to control depredating birds may be 

practiced, although such measures are prohibited 

by Mexican law. Lethal control of Gull-billed 

Terns and other larids at a shrimp farm near the 

town of El Golfo de Santa Clara, Sonora, in the 

extreme northern Gulf of California, was noted 

on 18 November 2002 (KCM). Gull-billed Terns 

are relatively abundant at shrimp ponds near 

Mazatlan and elsewhere in Sinaloa and the control 

of predatory birds, including Gull-billed Terns, 

occurs widely in Sinaloa (Molina and Erwin 2006). 

Although the extent and impact of such control on 

this species is unstudied, it could have significant 

population-level ramifications.

Table B-2. Number of breeding pairs of Gull-billed Terns at colonies in western Mexico (Sinaloa through 

Colima), 2000–2005. Dash (—) indicates no survey was conducted. Data from Palacios and Mellink 2007, X. 

Vega and M. A. Gonzalez, pers. comm., EM, EP.

Colony 2000 2001 2002 2003 2004 2005

Sinaloa

Bahia Santa María-Isla El Rancho 5 23 5 15 5 1–2

Laguna El Caimanero (Las Tres Tumbas) — — — — — 25

Nayarit

Estero Teacapan — — — 2 — 0

Laguna Pericos — — — 120–150 — 160

Colima

Laguna Cuyutlan (various small islets) — — — 15 — 55
Appendix B 65

UNITED STATES

California

Summary: California has the entire United States 

breeding population of G. n. vanrossemi. It is a 

localized breeder in two disjunct geographic areas 

in the extreme southern portion of the state: (1) 

inland in the immediate vicinity of the Salton Sea 

in Riverside and Imperial counties and (2) on the 

coast in southern San Diego Bay in San Diego 

County (Fig. B-3). The total breeding population in 

California has been fewer than 300 pairs since 2005. 

The Gull-billed Tern is a vagrant on the coast north 

of San Diego County: there are a few observation 

records from Bolsa Chica in Orange County 

(Hamilton and Willick 1996, McCaskie and Garrett 

2001, 2004), the Santa Clara River in Ventura 

County (B. Obst, pers. comm.), the Santa Ynez 

River in Santa Barbara County (Lehman 1994), and 

Venice Beach in Los Angeles County (McCaskie 

and Garrett 2005). There are a few mid-winter 

records for the south end of the Salton Sea, but this 

species is generally absent from California from late 

September through February.

Population Trends: Pemberton (1927) first 

documented the presence of the Gull-billed Tern at 

the Salton Sea in 1927, estimating the population to 

be 500 pairs. As summarized by Remsen (1978), the 

population declined to fewer than 200 pairs by 1937, 

from 40 to 75 pairs through the 1950s, and to only 

17 pairs in 1976. Since 1986, when 75 pairs were 

reported to have nested (Patten et al. 2003), Gullbilled Terns have rebounded and the population size 

at the Salton Sea has stabilized at 100 to 170 pairs 

annually during the period from 1992–2004 (Molina 

2004, KCM). Nesting has occurred primarily 

along the southern shore in up to four sites, with 

occasional nesting near the northeastern shore.

Gull-billed Terns first nested at the saltworks within 

the South San Diego Bay unit of the San Diego Bay 

NWR in 1986. The population increased to 30 pairs 

in 1992, varied between eight and 20 pairs through 

the remainder of the 1990s, and steadily climbed to 

52 pairs in 2006 (R. T. Patton, pers. comm.). Parnell 

et al. (1995) estimated the California population at 

less than 400 pairs, while recent surveys indicate 

that fewer than 300 pairs nest annually in the state 

(Tables 3, B-3).

Figure B-3. Locations and sizes of Gull-billed Tern colonies in California, 2003.
66 Status Review and Conservation Recommendations for the Gull-billed Tern

Research/Monitoring: Aspects of parental care, 

population trends, colony success, and colony site 

use in Gull-billed Terns breeding at the Salton Sea, 

as well as diet and foraging behavior in San Diego 

Bay were examined (Molina 1999, Molina 2004, 

KCM). Annual surveys have been conducted in 

San Diego Bay since 1986 and at the Salton Sea 

since 1991.

Conservation/Management Activities: Three colony 

sites occur on NWR lands. Signage or fencing is 

in place to restrict public access at these sites. 

Predator control is implemented at the San Diego 

Bay NWR colony site. Electric fencing is employed 

at one of the Sonny Bono Salton Sea NWR sites 

to deter mammalian predators. In 2003, the U.S. 

Fish and Wildlife Service sponsored a workshop to 

address standardized survey protocols for Gullbilled Terns in the United States and Mexico.

State Status: Species of Special Concern (California 

Department of Fish and Game 2008).

Natural Heritage Rank: S1—Critically Imperiled 

(NatureServe Explorer 2006).

Habitat Conditions: Gull-billed Terns at the Salton 

Sea nest on natural islands, sand and barnacle bars, 

and earthen levees surrounded by shallow water, 

and on constructed islets in wildlife impoundments. 

They forage over mudflats 

along the shoreline, alkali flats with low, sparse 

scrub, shallow drains and marshes, and dry and 

irrigated agricultural fields. In San Diego Bay, 

Gull-billed Terns nest on a network of earthen 

levees of the saltworks impoundments and forage 

along beach dunes, estuary mudflats, and the 

sandy intertidal zone.

Threats: The number of suitable nesting sites at 

the Salton Sea has declined with recession of water 

levels (Molina 2004), increasing disturbance or 

predation by raccoons and coyotes. Nest loss due to 

trampling by Brown and American White pelicans 

can be severe in some years. Water conservation 

measures (e.g., fallowing, tailwater recovery, drip 

irrigation) under the Imperial Irrigation District’s 

water transfer program will reduce inflows to 

the Salton Sea, thus contributing to lower water 

levels (J. A. Bartel, pers. comm.), the potential 

loss of nesting islands, and the degradation of 

foraging habitat.

In San Diego, Gull-billed Terns prey on the small 

chicks, and occasionally on the eggs of California 

Least Terns and Snowy Plovers, resulting in the 

removal of six Gull-billed Terns between 1993 and 

1995 (T. E. Tate-Hall, pers. comm.).

Table B-3. Number of breeding pairs of Gull-billed Terns at colonies in California, 1992–2006 (Molina 2004, R. 

T. Patton, pers. comm., KCM).

Colony 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006

San Diego Co.

San Diego NWR 30 10 12 10 n/a 8 8–10 11–20 20–27 30 32–36 32–37 40 43–48 52

saltworks

Imperial/Riverside Co.

Salton Sea 106 121 101 72 155 152 123 101 115 143 65 155 117 209 178–182

Totals 136 131 113 92 >155 162 131–133 112–121 135–142 173 97–101 187–192 157 240–259 230–234
Appendix B 67

McCaskie, G., and K. L. Garrett. 2004. The nesting 

season, southern Pacific Coast. North American 

Birds 57:545.

McCaskie, G., and K. L. Garret. 2005. Southern 

Pacific Coast. North American Birds 59:494.

Mellink, E., and G. de la Riva. 2005. Non-breeding 

waterbirds at Laguna de Cuyutlán and its 

associated wetlands, Colima, Mexico. Journal of 

Field Ornithology 76:158-167.

Molina, K. C. 1999. An evaluation of parental 

investment hypotheses using Gull-billed Terns 

and Black Skimmers (Aves: Laridae) at the 

Salton Sea, California. Master’s thesis. California 

State University, Northridge, California.

Molina, K. C. 2004. Breeding larids of the Salton 

Sea: trends in population size and colony site 

occupation. Studies in Avian Biology 27:92-99.

Molina, K. C., and R. M. Erwin. 2006. The 

distribution and conservation status of the 

Gull-billed Tern (Gelochelidon nilotica) in 

North America. Waterbirds 29:271-295.

Molina, K. C., and K. L. Garrett. 2001. The breeding 

birds of Cerro Prieto Geothermal Ponds, Mexicali 

Valley, Baja California. Monographs in Field 

Ornithology 3:23-28.

Munoz del Viejo, A., X. Vega, M. A. Gonzalez, and 

J. M. Sanchez. 2004. Disturbance sources, human 

predation, and reproductive success of seabirds 

in tropical coastal ecosystems of Sinaloa State, 

Mexico. Bird Conservation International 

14:191-202.

NatureServe Explorer. 2006. NatureServe 

Explorer: an online encyclopedia of life. 

<www.natureserve.org/explorer> 

(7 September 2009).

Palacios, E., and E. Mellink. 1993. Additional 

records of breeding birds from Montague Island, 

northern Gulf of California. Western Birds 

24:259-252.

Palacios, E., and E. Mellink. 1995. Breeding birds of 

Esteros Tobari and San Jose, southern Sonora. 

Western Birds 26:99-103.

Palacios, E., and E. Mellink. 2007. The colonies 

of vanRossem’s Gull-billed Tern (Gelochelidon 

nilotica vanrossemi) in Mexico. Waterbirds 

30:214-222.

Literature Cited, Appendix B

California Department of Fish and Game. 2008. 

California bird species of special concern. 

California Department of Fish and Game. 

<www.dfg.ca.gov/wildlife/nongame/ssc/birds.

html> (28 September 2009).

Danemann, G. D., and R. Carmona. 2000. Breeding 

birds of the Guerrero Negro saltworks, Baja 

California Sur, Mexico. Western Birds 31:195-199.

Erickson, R. A., R. A. Hamilton, and S. N. G. 

Howell. 2001. New information on migrant birds 

in northern and central portions of the Baja 

California peninsula, including species new to 

Mexico. Monographs in Field Ornithology 

3:112-170.

Erickson, R. A., R. A. Hamilton, E. Palacios, and 

R. Carmona. 2003. The winter season, Baja 

California Peninsula. North American Birds 

57:260-262.

Escalante, B. P. 1988. Aves de Nayarit. Universidad 

Autonoma de Nayarit, Tepic, México.

Friedmann, H., L. Griscom, and Moore, R. T. 1950. 

Distributional checklist of the birds of Mexico. 

Pacific Coast Avifauna 29.

Gonzalez-Bernal, M. A., X. Vega, and E. Mellink. 

2003. Nesting of Western Gulls in Bahia de Santa 

Maria-La Reforma, Sinaloa, Mexico. Western 

Birds 34:175-176.

Grinnell, J. 1928. A distributional summation of the 

ornithology of Lower California. University of 

California Publications in Zoology 32:1-300.

Hamilton, R. A., and D. R. Willick. 1996. The 

birds of Orange County, California: status and 

distribution. Sea and Sage Audubon Society, 

Sea and Sage Press, Irvine, California.

Howell, S. N. G., and S. Webb. 1995. A guide to the 

birds of Mexico and northern Central America. 

Oxford University Press, Oxford, England.

Lehman, P. E. 1994. The birds of Santa Barbara 

County, California. Vertebrate Museum, 

University of California, Santa Barbara, 

California.

McCaskie, G., and K. L. Garrett. 2001. The spring 

migration, southern Pacific Coast. North 

American Birds 55:356.
68 Status Review and Conservation Recommendations for the Gull-billed Tern

Parnell, J. F., R. M. Erwin, and K. C. Molina. 

1995. Gull-billed Tern (Sterna nilotica). In

A. Poole and F. Gil, editors. The Birds of 

North America, No. 140. Academy of Natural 

Sciences, Philadelphia, Pennsylvania; American 

Ornithologists’ Union, Washington D.C.

Patten, M. A., G. McCaskie, and P. Unitt. 2003. Birds 

of the Salton Sea: status, biogeography, and 

ecology. University of California Press, Berkeley, 

California.

Pemberton, J. R. 1927. The American Gull-billed 

Tern breeding in California. Condor 29:253-258.

Peresbarbosa, E., and E. Mellink. 2001. Nesting 

waterbirds of Isla Montague, northern Gulf of 

California, Mexico: loss of eggs due to predation 

and flooding, 1993–1994. Waterbirds 24:265-271.

Remsen, J. V., Jr. 1978. Bird species of special 

concern in California. California Department 

of Fish and Game, Nongame Wildlife 

Investigations, Wildlife Management Branch 

Administrative Report 78-1, Sacramento, 

California.

Schaldach, W. J., Jr. 1963. The avifauna of Colima 

and adjacent Jalisco, Mexico. Proceedings of the 

Western Foundation of Vertebrate Zoology 1:1-

100.

van Rossem, A. J. 1945. Birds of Sonora. Louisiana 

State University Press, Baton Rouge, Louisiana.
Appendix C 69

Appendix C: State and Regional Contacts 

and Contributors

David H. Allen

North Carolina Wildlife Resources Commission

183 Paul Drive

Trenton, NC 28585

Phone: (252) 448-1546

E-mail: david.h.allen@ncwildlife.org

J. Steve Calver

U.S. Army Corps of Engineers

Savannah District (PD-EC)

100 West Oglethorpe

Savannah, GA 31401-3640

Phone: (912) 652-5797

E-mail: james.s.calver@usace.army.mil

Susan E. Cameron

North Carolina Wildlife Resources Commission

253 White Oak Bluff Road

Stella, NC 28582

Phone: (910) 325-3602

E-mail: camerons@coastalnet.com

Steven W. Cardiff

Sections of Ornithology and Mammalogy

Museum of Natural Science

119 Foster Hall

Louisiana State University

Baton Rouge, LA 70803-3216

Phone: (225) 578-9289

E-mail: scardif@lsu.edu

Roger B. Clay

Alabama Division of Wildlife and Freshwater 

Fisheries

30571 Five Rivers Boulevard

Spanish Forks, AL 36527

Phone: (251) 626-5474

E-mail: rclay@dcnr.state.al.us

Brian E. Collins

U.S. Fish and Wildlife Service

San Diego National Wildlife Refuges Coastal 

Refuge Complex

Chula Vista, CA 91910

Phone: (619) 691-1262

E-mail: brian_collins@fws.gov

Michelle L. Gibbons

New York State DEC, Bureau of Wildlife

SUNY @ Stony Brook

50 Circle Road

Stony Brook, NY 11790-3409

Phone: (631) 444-0306

E-mail: mlgibbon@gw.dec.state.ny.us

Mark A. Goodman

Mississippi State University

P. O. Box PF

Mississippi State, MS 39762

Phone: (662) 325-7953

E-mail: mg654460@yahoo.com

Joe A. Halbrook

4680 Barton

Beaumont, TX 77706-2730

Phone: (409) 892-3090

E-mail: joebmt@sbcglobal.net

Howard Horne

Barry A. Vittor & Associates, Inc.

8060 Cottage Hill Road

Mobile, AL 36695

Phone: (251) 633-6100

E-mail: hhorne@bvaenviro.com

Gregory D. Jackson

2220 Baneberry Drive

Birmingham, AL 35244-1403

Phone: (205) 987-2855

E-mail: g_d_jackson@bellsouth.net

C. David Jenkins, Chief

New Jersey Division of Fish and Wildlife

Endangered and Nongame Species Program

501 E. State Street

Trenton, NJ 08625-0400

Phone: (609) 292-9101

E-mail: dave.jenkins@dep.state.nj.us

Paul L. Leberg

Department of Biology

University of Louisiana

P.O. Box 42451

Lafayette, LA 70504

Phone: (337) 482-6637

E-mail: leberg@louisiana.edu
70 Status Review and Conservation Recommendations for the Gull-billed Tern

Mary P. Stevens

Mississippi Museum of Natural Science

2148 Riverside Drive

Jackson, MS 39202-1353

Phone: (601) 354-7303

E-mail: library@mmns.state.ms.us

Barry R. Truitt

The Nature Conservancy, Virginia Coast Reserve

11332 Brownsville Road

Nassawadox, VA 23413

Phone: (757) 442-3049

E-mail: btruitt@tnc.org

Vincent V. Turner

U.S. Fish and Wildlife Service

Edwin B. Forsythe National Wildlife Refuge

P.O. Box 72

800 Great Creek Road

Oceanville, NJ 08231

Phone: (609) 748-1535

E-mail: vinny_turner@fws.gov

Xicotencatl Vega Picos

Manomet Center for Conservation Sciences

ITESM, Campus Sinaloa

Blvd. Culiacan No. 3771 Pte. C. P. 80000

Culiacan, Sinaloa, Mexico

Phone: (667) 759-1616

E-mail: xicovega@manomet.org

Michael R. Wasilco

New York State Department of Environmental 

Conservation

Division of Fish, Wildlife, and Marine Resources

6274 E. Avon-Lima Road

Avon, NY 14414-9519

Phone: (585) 226-5460

E-mail: mrwasilc@gw.dec.state.ny.us

Bryan D. Watts

Center for Conservation Biology

College of William and Mary

Williamsburg, VA 23187

Phone: (757) 221-2247

E-mail: bdwatt@wm.edu

Jennifer K. Wilson

U.S. Fish and Wildlife Service

Texas Mid-Coast National Wildlife Refuge Complex

2547 CR 316

Brazoria, TX 77422

Phone: (979) 964-4011 Ext. 34 

E-mail: jennifer_wilson@fws.gov

Brad Winn

Georgia Department of Natural Resources

Nongame Conservation

One Conservation Way, Suite 310

Brunswick, GA 31520

Phone: (912) 262-3128

E-mail: brad_winn@dnr.state.ga.us

Tim Manolis

808 El Encino Way

Sacramento, CA 95864

Phone: (916) 485-9009

E-mail: Ylightfoot@aol.com

Robert W. McFarlane

McFarlane & Associates

2604 Mason St

Houston, TX 77006

Phone: (713) 524-2927

E-mail: rwmcf@swbell.net

Thomas C. Michot

U.S. Geological SurveyNational Wetlands Research Center

700 Cajundome Boulevard

Lafayette, LA 70506

Phone: (337) 266-8664

E-mail: michott@usgs.gov

Robert T. Patton

4444 La Cuenta

San Diego, CA 92124

Phone: (858) 560-0923

E-mail: rpatton@san.rr.com

Elisa Peresbarbosa

Pronatura Veracruz

Diego Rivera No. 49 Fraccionamiento Coapexpan 

C.P. 91070 Xalapa,

Veracruz, México

Phone: (228) 817-9617

E-mail: humedales@pronaturaveracruz.org

Robert D. Purrington

Department of Physics

Tulane University

New Orleans, LA 70118

Phone: (504) 862-3177

E-mail: danny@tulane.edu

James A. Rodgers, Jr.

Florida Fish and Wildlife Conservation Commission

1105 SW Williston Road

Gainesville, FL 32601

Phone: (352) 955-2081 x127

E-mail: james.rodgers@myfwc.com

Martha Román

Comisión de Ecología y Desarrollo Sustentable del 

Estado de Sonora

Ave. Jalisco 903, entre 9 y 10, Colonia Sonora

San Luis Río Colorado, Sonora, México 83440

Phone: (011-52) (653) 536-8131

E-mail: romanmaju@gmail.com

Christian C. Schoneman

Sonny Bono Salton Sea National Wildlife Refuge 

Complex

906 W. Sinclair Road

Calipatria, CA 92233

Phone: (760) 348-5278, x227

E-mail: christian_schoneman@fws.gov

U.S. Department of the Interior

U.S. Fish & Wildlife Service

Route 1, Box 166

Shephardstown, WV 25443

www.fws.gov

June 2010