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Sandwich Tern | Thalasseus sandvicensis
Grote stern | Charrán patinegro
The Sandwich Tern is a medium-sized crested tern seen along coasts throughout the Caribbean. American birds are treated by some authorities as a separate species, Cabot's Tern Thalasseus acuflavidus, with the yellow-billed form from northern South America, Cayenne Tern T. a. eurygnathus, as a subspecies; this guide follows the broader concept. On the ABC Islands both forms breed side by side and intermediates occur.
Voice
A loud, grating kirr-ick or kerr-rick, often in flight; at the colony a constant hoarse screeching.
Recording: Paul Kelly — CC BY-NC-SA 4.0 · converted to mono · xeno-canto
Identification
37–43 cm, slender, with long, narrow wings, a short forked tail and a long, thin bill. In the northern form the bill is black with a yellow tip; in Cayenne Tern it is wholly yellow to orange-yellow, and intermediates have a mottled bill. In breeding plumage there is a black cap with a shaggy crest on the hindcrown; from early in the season and through the winter the forehead is white, leaving only a black-speckled hindcrown. Upperparts very pale grey, underparts white. Legs black. Juveniles have dark V-shaped marks on the back and wings and a shorter, all-dark bill.
Confusion species
Royal Tern Thalasseus maximus is clearly larger, with a thick orange bill; a yellow-billed Cayenne Tern, however, is slimmer, with a thinner, slightly paler bill. Elegant Tern Thalasseus elegans, a very rare vagrant, has a long, slightly drooping orange bill and a longer crest. Gull-billed Tern Gelochelidon nilotica has a short, thick, all-black bill and no crest.
Habitat
Coastal waters, shallow bays, the outer edge of reefs and the margins of sandbars. It fishes by plunge-diving from a few metres up, mainly for small schooling fish. It rests on beaches, jetties, buoys and rocks. It breeds in dense colonies on bare or sparsely vegetated islets and coral cays, often together with Royal Terns.
Where the bird is most at home, classified by the vegetation types of the Caribbean.
Range and movements
Breeds on small islets in the Bahamas, Cuba, the cays around Puerto Rico, the Virgin Islands, Anguilla and Sint Maarten and in the southern Lesser Antilles, and on the reef islets of Aruba, Curaçao and Bonaire. Beyond these, it is seen throughout the region as a winter visitor and passage migrant from North America and as a post-breeding wanderer, most numerous around Puerto Rico, Cuba and the ABC Islands. Regular on Trinidad and Tobago. Outside the region the American form breeds from the east coast of the United States to Mexico and Central America and along the coasts of South America; the nominate form breeds in Europe and winters in Africa.
- Resident
- Summer visitor (c. Oct–Mar)
- Winter visitor (c. Apr–Sep)
- Passage (Mar–Apr, Oct–Nov)
- dark = core range, pale = thinly spread
How and when to look
Harbours, jetties and sandbars near the shore are where birds rest and can be studied closely. On Aruba and Curaçao a resting flock of terns is the place to look at the variation in bill colour between northern birds, Cayenne Terns and intermediates. In flight the grating call often draws attention before the bird does.
Conservation status
Not threatened. Colonies on low islets are vulnerable to disturbance, egg collecting, introduced rats and flooding during storms and from sea-level rise. Nesting sites are protected on several islands.
Scientific name
Thalasseus sandvicensis | (Latham, 1787)
Latham described the species in 1787 as Sterna sandvicensis; because it was later moved to another genus, the author and year stand in brackets. The genus Thalasseus was introduced in 1822 by Boie. Thalasseus derives from Ancient Greek thalassa 'sea'. sandvicensis means 'of Sandwich', the town in the English county of Kent that was the type locality. The specimen the first description was based on came from Sandwich, Kent, England.