Sooty tern

Voice

Noisy at the colony, with a nasal, far-carrying ker-wack-wack written in English as wide-awake, which gave the bird its old name of Wideawake Tern. Vagrants are usually silent, though one lifting from a tern roost may call once.

Identification

A large, long-winged tern with black upperparts cut sharply against white underparts. The white forehead patch is broad but stops at the eye, and a black line runs from the cap to the bill. The tail is deeply forked with white outer feathers, the bill and legs are black, and the underwing is white with a dark trailing edge. Juveniles are sooty brown throughout with pale scaling on mantle and coverts and look nothing like the adult.

Confusion species

Bridled Tern is the only real problem. The back settles it: black on Sooty Tern, grey-brown and clearly paler than the cap on Bridled. The white forehead is broader on Sooty but ends at the eye, whereas on Bridled it carries on behind the eye as a narrow white brow. Bridled also shows a white collar between cap and mantle, which Sooty lacks, and more white in the outer tail feathers. Against Arctic Tern at sea the gap is wide: Arctic is smaller and pale grey above, with a translucent hand and a blood-red bill, while both tropical terns are black above and white below and fly on slower, more elastic beats.

Habitat

Open ocean, often over schools of tuna that drive small fish and squid to the surface; the birds snatch prey in flight and hardly ever dive. Colonies are on flat sand and coral islands and sometimes on bare lava. In Europe the few records are on beaches, groynes and sandbanks among Sandwich Terns after onshore gales.

Range and movements

Breeds in all tropical oceans, the nearest colonies to Europe being on Ascension, in Cape Verde and in the Red Sea. European records are thinly scattered across Britain and Ireland, France, Iberia and, rarely, the Low Countries, with almost all falling between June and September. Some birds ride north with the remains of tropical cyclones.

• Breeding (summer)
• Passage
• Migration direction
• dark = core range, pale = thinly spread

Where and when to look

July and August after a spell of south-westerly weather give the best chance. Work resting Sandwich Tern flocks on sandbanks and groynes and judge the bird on size and on the hard line between black upperparts and white underparts rather than on general darkness, because a dark tern in a European roost is far more often a Black Tern.

Conservation status

Not globally threatened, with a population in the tens of millions, but individual colonies are fragile. Introduced rats and cats, egg harvesting and shifts in the fish and squid the birds depend on have caused steep declines on several islands, Ascension among them.