Atlantic White-Tern

The Atlantic white tern is 23–30 cm (9.1–11.8 in) long with a wingspan of 76–87 cm (30–34 in). It has pure white plumage, except for a dark streak along the shafts of the outer primary feathers in G. a. candida), a black eye accentuated by a narrow ring of black feathers round the eye, and a long black to bluish-black bill. The tail is shallowly forked, but like in the noddies, with the longest feathers the second-from outermost, not the outermost as in other terns. The legs are dark grey, to paler grey in G. a. leucopes and G. a. microrhyncha. The juvenile is white mottled with grey or greyish-brown. Nesting on coral islands, usually on trees with small branches but also on rocky ledges and on man-made structures, the white tern feeds on small fish which it catches by plunge diving.

The Atlantic white tern is found on certain remote islands in the South Atlantic. It is a pelagic and epipelagic bird, living along the coast and moving into wooded areas during the breeding season.

This species is notable for laying its egg on bare thin branches in a small fork or depression without a nest. This behaviour is unusual for terns, which generally nest on the ground, and even the related tree-nesting black noddy constructs a nest. It is thought that the reason for the absence of nests is the reduction in nest parasites, which in some colonial seabirds can cause the abandonment of an entire colony. In spite of these benefits there are costs associated with tree nesting, as the eggs and chicks are vulnerable to becoming dislodged by heavy winds. For this reason the white tern is also quick to lay a replacement should it lose the egg. The newly hatched chicks have well-developed feet with which to hang on to their precarious nesting site. It is a long-lived bird, having been recorded living for 42 years.