Cabot's Tern

The Cabot's tern, Thalasseus acuflavidus, is a sleek seabird belonging to the "crested tern" group. It measures between 34 to 45 cm in length, with a wingspan of approximately 1 meter. The bird exhibits sexual monomorphism, meaning males and females share the same plumage, which is predominantly white with a pale gray back. During breeding season, adults don a striking black cap, and their tail is characteristically forked and white. The upper side of their wing is mostly pale gray with darker primaries, and they may exhibit a rosy flush on the underparts. Their legs and feet are black or black with yellow soles, and their iris is dark brown to black.

Identification Tips

In breeding plumage, the adult Cabot's tern can be identified by its black cap and pale gray back. The bill is a notable feature for distinguishing between subspecies; the nominate T. a. acuflavidus has a black bill with a yellow tip, while T. a. eurygnathus sports a mostly to completely yellow bill. In non-breeding plumage, adults have a white forehead and mid-crown with a black crest.

Habitat

Cabot's tern is strictly coastal, favoring warm waters. Breeding habitats include barrier islands, dredge spoil islands, and low-lying sand or coral cays with sparse vegetation. In winter, they are found on sand beaches, sandbars, barrier islands, and reefs.

Distribution

This tern breeds along the U.S. coast from Chesapeake Bay southward, around the Gulf of Mexico to Belize, the Bahamas, the Greater Antilles, and other Caribbean islands. It winters in southern Florida, the Gulf and Caribbean coasts, the Antilles, and South America, with some reaching as far as Chile or northern Brazil.

Behaviour

The Cabot's tern is partially migratory, retreating from the northern extremes of its breeding range in winter. It is a powerful flyer, often foraging in small flocks close to shore, and is known for its plunge-diving feeding technique.

Song & Calls

The main call of the Cabot's tern has been described as a "kerr-ick," "kjerr-it," "keerik," or "kreejik." It also has a repertoire of other calls used in various contexts.

Breeding

Pairs are formed during spring migration, with males performing display flights or ground posturing. Nesting occurs on the ground with little to no vegetation, and the clutch typically consists of one to two eggs. Both sexes share incubation duties, and chicks are semi-precocial, relying on their parents for food until they fledge at about 27 to 29 days old.

Similar Species

The Cabot's tern can be confused with the sandwich tern, but can be differentiated by its bill color and breeding range.

Diet and Feeding

The diet of Cabot's tern is predominantly fish, including species from the families Ammodytidae, Atherinopsidae, Clupeidae, Engraulidae, and Sciaenidae. It also consumes squid, shrimp, and insects.

Conservation Status

The IUCN has not assessed the Cabot's tern separately from the sandwich tern sensu lato. Human disturbance of nesting colonies is considered the primary threat to the species.