Chlidonias leucopterus - White-winged Black Tern
Feather characters. Barbules are rather short (0.67-0.77 mm). Pigmentation varies in different body feathers, it is absent or concentrated in nodes and parts of internodes (less than 50%). Slightly thickened nodes (20-22 per mm) are equally distributed along the entire length of barbules, only slightly decreasing in size towards distal end. Villi are absent and internodes are occasionally kinked. Minute prongs may be present along the entire length of barbules, on both sides of the pennulum. These prongs are unequally distributed, and many nodal structures without prongs may be found.
Field characters. Size 24 cm. Weight 54 g (42.0-66.0) (Dunning, 1993). Like Black Tern (Chlidonias niger, not included in BRIS), but bill slightly shorter and tail slightly less forked. In breeding plumage easy to identify: body mainly black, but upperwings, especially forewing, silvery white, while underwing coverts are completely black. Under tail-coverts, rump, and tail very light grey, almost appearing white. Legs red. In winter plumage, looks more like Black Tern, but White-winged Black Tern is whiter; the crown is mottled black and only the ear-coverts are completely black, while Black Tern has a complete black hood. Furthermore, the black shoulder marks from Black Tern are absent in White-winged Tern, and White-winged has paler upperwing with contrasting dark outer primaries and secondaries. Juveniles with a black back, forming a saddle which contrasts with the greyer wings (more contrast than in Black Tern). The rump is white, not grey like in Black Tern and, like adult in winter, it lacks the black shoulder marks. Because of the shorter bill and smaller amount of black on the head in both adult winter plumage and juvenile look somewhat like Little Gull (Larus minutus, not included in BRIS). Flight and habits as Black Tern.
Voice. Calls similar to those of Black Tern, but less piercing: 'keer', 'churr', 'kreek'.
Distribution. Summer visitor. Rare, but locally common in eastern Europe and western Asia. More common on migration, when singles can be found in flocks of migrating Black Terns. Map: see MapIt.
Habitat. Standing freshwater marshes and lakes with plenty of vegetation during breeding season; on migration and in winter, frequents large water bodies, marshes, rivers and coasts.
Food. Mainly insects and other invertebrates, but some fish and small vertebrates also taken.