USGS



BIOLOGICAL AND ECOTOXICOLOGICAL CHARACTERISTICS OF TERRESTRIAL VERTEBRATE SPECIES RESIDING IN ESTUARIES

Gull-billed Tern Gull-billed Tern photo by Jim Stasz
(Photo by Jim Stasz)
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Biological Characteristics

Species Gelochelidon nilotica is about 33-38 cm in length and has an average mass of 233 grams (Dunning, 1993). Body mass appears to be similar between sexes (Parnell et al., 1995). During the breeding season, this bird has a white back and wings, black cap and stout black bill. During the non-breeding season, gull-billed terns lack the black cap (Bull and Farrand, 1977).
Status in Estuaries

This species breeds colonially, often with other terns and skimmers, in coastal marshes and sandy beaches, occasionally in the presence of other species of terns. Two to three spotted buff eggs are laid in a shell-lined shallow depression or occasionally a well-made cup of dead marsh grass. Young are semiprecocial (Ehrlich et al., 1988). The maximum age of a gull-billed tern recorded in nature 15 years (Clapp et al., 1983).

Abundance and Range During the breeding season this species is found from Long Island to the Gulf of Mexico. In 1976 and 1977 approximately 5,400 individuals were counted in 83 coastal colonies (Spendelow and Patton, 1988). In the southeast U.S., 3,019 pairs were counted, and the authors suspected that this number represented 95% of U.S. population (Clapp and Buckley, 1984). During the non-breeding season this species is found in South Florida and through the Gulf of Mexico (Bull and Farrand, 1977).
Site Fidelity

Weak from year to year (Moller, 1978, 1982)

Ease of Census Simple.
Feeding Habits Generalist. Gull-billed terns feed by "aerial-dipping" in which the bird surveys the feeding area by passing back and forth, then dives down to pluck the prey item from land or water (Clapp et al., 1983). This species is capable of exploiting locally abundant prey including many kinds of terrestrial and aquatic species. Specific preferences include invertebrates and worms in plowed fields, fish and crustaceans.

Gull-billed Tern Contaminant Exposure Data

I.

Organochlorine Contaminants

1.

In 1970, ten gull-billed tern eggs were collected from various locations in Texas (King et al., 1978). Mean contaminant concentrations were 4.89 mg/g wet weight sigma.gif (58 bytes)DDT (sum of DDD, DDE and DDT), 0.18 mg/g dieldrin, and 1.25 mg/g PCB.

2.

From 1972 to 1975, 37 tern eggs were collected from South Carolina (Blus and Stafford, 1980). Geometric means for DDE ranged from 0.23 mg/g wet weight in 1975 to 0.94 mg/g in 1972. DDE was highest (10.71 mg/g) in an individual collected in 1972. Dieldrin, mirex, oxychlordane were detected at low levels, and trans-nonachlor was not detected in any eggs. Total PCBs ranged from not detected to 30.1 mg/g in an individual collected in 1972.

II.

Cholinesterase-Inhibiting Pesticides

 

No direct exposure data available

III.

Trace Elements, Metals, and Metalloids

 

No concentration data available

IV.

Petroleum

 

No residue data available

Gull-billed Tern Contaminant Response Data

I.

Organochlorine Contaminants

1.

To determine average shell thickness, 58 tern eggs were collected from Texas in 1970 (King et al., 1978). There was a significant 3% decrease in shell thickness between eggs collected in 1970 and the thickness of 31 eggs collected prior to 1943.

2.

Abnormal (cracked or crushed) eggshells were observed in samples containing >7 mg/g wet weight DDE (Blus and Stafford, 1980).

II.

Cholinesterase-Inhibiting Pesticides

 

No response data available

III.

Trace Elements, Metals, and Metalloids

 

No response data available

IV.

Petroleum

 

No response data available

References for Gull-Billed Tern

Blus, L.J. and C.J. Stafford. 1980. Breeding biology and relation of pollutants to black skimmers and gull-billed terns in South Carolina. U.S. Fish Wildl. Serv., Spec. Sci. Rep.--Wildl. No. 230. 18 p.

Bull, J. and J. Farrand, Jr. 1977. The Audubon Society Field Guide to North American Birds. Alfred A. Knopf, New York.

Clapp, R.B. and P.A. Buckley. 1984. Status and conservation of seabirds in the southeastern United States. In J.P. Croxall, P.G.H. Evans, and R.W. Schreiber, eds. Status and conservation of the world's seabirds. Tech Publ. No. 2., Internl. Council Bird Preserv., Cambridge, UK, pp. 135-155.

Clapp, R.B., D. Morgan-Jacobs, and R.C. Banks. 1983. Marine birds of the southeastern United States and Gulf of Mexico. Part III: Charadriiformes. U.S. Fish and Wildlife Service, Office of Biological Services, Washington, D.C. FWS/OBS-83/30. 853 pp.

Dunning, Jr., J.B., ed. 1993. CRC Handbook of Avian Body Masses. CRC Press, Ann Arbor. 371 pp.

Ehrlich, P.R., D.S. Dobkin, and D. Wheye. 1988. The Birder's Handbook. Simon & Schuster, New York. 785 pp.

King, K.A., E.L. Flickinger, and H.H. Hildebrand. 1978. Shell thinning and pesticide residues in Texas aquatic bird eggs, 1970. Pestic. Monitor. J. 12:16-21.

Moller, A. P. 1978. Deserting flights in the gull-billed tern (Gelochelidon nilotica) with special reference to the Danish population. Dan. Ornithol. Foren. Tidssk. 72:119-126.

Moller, A.P. 1982. Coloniality and colony structure in the gull-billed terns Gelochelidon nilotica. Ornithol. 123:41-53.

Parnell, J.F., R.M. Erwin, and K.C. Molina. 1995. Gull-billed Tern. The Birds of North America, No. 140. The Academy of Natural Sciences of Philadelphia. 20 pp.

Spendelow, J.A. and S.R. Patton. 1988. National atlas of coastal waterbird colonies in the contiguous United States: 1976-82. U.S. Fish Wildl. Serv. Biol. Rep. 88(5). 326 pp.

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