charrán patinegro (Thalasseus sandvicensis) Sandwich tern

his is a medium-large tern, 37–43 cm (15–17 in) long with an 85–97 cm (33–38 in) wingspan, which is unlikely to be confused within most of its range, al...
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his is a medium-large tern, 37–43 cm (15–17 in) long with an 85–97 cm (33–38 in) wingspan, which is unlikely to be confused within most of its range, although the South American race could be confused with the elegant tern.

The Sandwich tern's thin sharp bill is black with a yellow tip, except in the yellow or orange billed South American race. Its short legs are black. Its upperwings are pale grey and its underparts white, and this tern looks very pale in flight, although the primary flight feathers darken during the summer.
The lesser crested tern and elegant tern differ in having all-orange bills; lesser crested also differs in having a grey rump and marginally stouter bill, and elegant in having a slightly longer, slenderer bill. Chinese crested tern is the most similar to Sandwich, but has a reversal of the bill colour, yellow with a black tip; it does not overlap in range with Sandwich tern so confusion is unlikely.

In winter, the adult Sandwich tern's forehead becomes white. Juvenile Sandwich terns have dark tips to their tails, and a scaly appearance on their back and wings, like juvenile roseate terns.
The Sandwich tern is a vocal bird; its call is a characteristic loud grating kear-ik or kerr ink.
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