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Forster's Tern | Sterna forsteri
Forsters stern | Charrán de Forster
Forster's Tern breeds almost exclusively in North America, in marshes inland and along the coast. It winters from the southern United States to Central America and reaches the Caribbean mainly in the north-west, on Cuba, the Bahamas and the Cayman Islands. In winter plumage it is the tern with a black 'mask' through the eye.
Voice
A low, nasal, descending kyarr or kerr, lower and rougher than in Common Tern; when threatened a hoarse zaar.
Recording: Valerie Heemstra — CC BY-NC-SA 4.0 · converted to mono · xeno-canto
Identification
33–36 cm, slim, with a long, deeply forked tail, fairly long legs and a thin bill. In breeding plumage it has a full black cap, an orange bill with a black tip and orange-red legs; the upper surface of the primaries is silvery white, paler than the back. In winter plumage, in which birds usually appear here, the head is white with a rounded black patch through and behind the eye, and the bill is black; the hindcrown is white or pale greyish. Upperparts pale grey, rump white and tail grey with white outer edges. First-year birds resemble winter adults, with darker primaries and a shorter tail.
Confusion species
Common Tern Sterna hirundo in winter has a black band from the eye round the hindcrown rather than an isolated eye patch, a dark wedge in the primaries, a dark carpal bar and shorter legs. Gull-billed Tern Gelochelidon nilotica also shows a dark eye patch in winter but is stockier, with a thick, short black bill, a shorter tail and black legs. Sandwich Tern Thalasseus sandvicensis is larger, with a shaggy crest and a yellow bill tip.
Habitat
Sheltered, shallow coastal waters: lagoons, salt pans, shallow bays, mudflats and estuaries, and also brackish and fresh pools inland and canals near the coast. It hunts by hovering and plunge-diving for fish, and also catches insects over the water. It rests on posts, buoys and sandbars.
Where the bird is most at home, classified by the vegetation types of the Caribbean.
Range and movements
On Cuba, the Bahamas and the Cayman Islands a scarce but regular winter visitor. Rare on Puerto Rico and Jamaica, with only a handful of records from San Andrés, the Turks and Caicos Islands, Hispaniola, Guadeloupe, Sint Maarten, St Kitts, St Vincent, the Virgin Islands and Aruba. Outside the region it breeds in the prairie marshes of Canada and the United States and along the Atlantic and Gulf coasts; it winters from the southern United States to Guatemala and Honduras.
- Resident
- Winter visitor (c. Apr–Sep)
- dark = core range, pale = thinly spread
How and when to look
The lagoons and salt pans along Cuba's north coast and the shallow waters of the Bahamas in winter give the best chance. The rounded black eye patch on a white head is the quickest giveaway; a bird with a black band linking the eye patch to the hindcrown is more likely a Common Tern.
Conservation status
Not threatened. The population is fairly stable, but on the breeding grounds the species depends on marshes, which are being degraded by drainage and changes in water levels.
Scientific name
Sterna forsteri | Nuttall, 1834
Nuttall described the species in 1834 and placed it straight away in the genus where it still stands. The genus Sterna was introduced in 1758 by Linnaeus. Sterna goes back to Old English stearn, which appears in the poem The Seafarer; the Frisians used a related word for terns. forsteri honours the German naturalist Johann Reinhold Forster (1729–1798), who sailed with Cook on his second voyage. The specimen the first description was based on came from the Saskatchewan River, Canada.