Black Tern

IDENTIFICATION: In breeding plumage, this small tern is dark gray with a black head and undersides, and a slightly forked tail. In fall migration and winter plumage, it is white below, with a white collar and a partial black hood. Length: 23-26 cm.; weight: 50-60 g.

VOICE: The call is a squeaky, "kip." Audio (M. Oberle).

HABITAT: Migrates through the Caribbean where flocks sometimes rest on beaches, pilings and mudflats, or forage on ponds and lagoons.

HABITS: The Black Tern passes through the region in flocks of up to 200 birds, feeding on small fish, plankton and insects close to shore or at ponds during migration. It winters at sea, often within a few kilometers of shore, but switches its habitat entirely when it nests on freshwater lakes and ponds in inland northern North America, especially in the northern Prairie states and provinces. In the breeding season, a high proportion of its diet may consist of insects, including flies and moths caught in mid-air or from the waterÆs surface. It also follows farm tractors to take advantage of fleeing insects. The Black Tern congregates in loose breeding colonies in marshes where both sexes build a nest on a floating mat of vegetation. The eggs have more pores than other tern eggs---possibly an adaptation to keep the eggs from getting waterlogged in the moist environment of the nest. Both sexes incubate the 2-3 eggs for about 21 days, and both feed the chicks. After the young fledge 20-28 days after hatching, the family moves to open water and defends a feeding territory where the young learn to forage on their own. Will start to breed at two years of age.

STATUS AND CONSERVATION: An uncommon migrant, with less frequent sightings in winter (e.g. 28 December 1998 at the Arecibo docks). Population levels have declined dramatically in the 20^th Century, probably due to drainage of wetlands in the breeding range. But pesticides are also a suspected cause of breeding failures.

RANGE: Breeds in marshes of the northern USA and southern Canada. It winters off the Pacific coast of Central America, south to Peru, and off the Atlantic coast of Panamá east to the Guianas.

TAXONOMY: CHARADRIIFORMES; LARIDAE; Sterninae

Non-breeding plumage - Photo: G. Lasley

References

Bent, A.C. 1921. Life histories of North American gulls and terns. Smithsonian Instit. U.S. National

Museum Bull. 113. (Reprinted by Dover Press, 1963).

del Hoyo, J., A. Elliott, and J. Sargatal, eds. 1996. Handbook of Birds of the World, Vol. 3. Hoatzin to Auks. Lynx Edicions, Barcelona.

Dunn, E. H. and D. Agro. 1995. Black Tern (Chlidonias niger). No. 147 in The birds of North America (A. Poole and F. Gill, eds.). Acad. Nat. Sci., Philadelphia, PA, and Am. Ornithol. Union, Washington, D.C.

Ehrlich, P.R., D.S. Dobkin, and D. Wheye. 1988. The birder's handbook: a field guide to the natural history of North American birds. Simon and Schuster/ Fireside, NY.

Harrison, P. 1983. Seabirds: an identification guide. Houghton Mifflin, Boston.

Harrison, P. 1987. A field guide to seabirds of the world. Stephen Greene Press, Lexington, MA.

Raffaele, H.A. 1989. A guide to the birds of Puerto Rico and the Virgin Islands. Princeton.

Raffaele, H.A. 1989. Una guía a las aves de Puerto Rico y las Islas Vírgenes. Publishing Resources, Inc., Santurce, PR.

Raffaele, H.A., J.W. Wiley, O.H. Garrido, A.R. Keith, and J.I. Raffaele. 1998. Guide to the birds of the West Indies. Princeton.

Black Tern, Spanish text

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