Black Tern

The Black Tern is a small, dark marsh tern that breeds on freshwater wetlands across the Northern Hemisphere and is notable for its dramatic seasonal plumage change. Unlike the typical coastal terns, it spends much of its breeding life over inland marshes and lakes.

Appearance

In breeding plumage, adults are strikingly dark, with a sooty black head and underparts, slate-gray wings and back, and white undertail coverts. In non-breeding plumage and in juveniles, the bird becomes largely white below with a dark cap, dark smudge on the side of the breast, and gray upperparts, looking quite different from the summer bird.

Key field marks

• Breeding adults: black head and underparts contrasting with gray wings and back
• Non-breeding and juvenile birds: white underparts, dark cap, and a dark shoulder smudge
• Small size and buoyant, erratic flight low over water
• Short, slightly forked tail

Similar species

Whiskered Tern is larger and paler with a shorter, more contrasting white cheek stripe in breeding plumage. White-winged Tern (a close relative) has a whiter tail and black underwing coverts in breeding plumage, unlike the gray underwings of Black Tern. Non-breeding Black Terns can resemble small Common Terns but are smaller with a distinctive dark breast-side smudge.

Habitat and range

Black Terns breed on shallow freshwater marshes, lakes, and ponds with emergent vegetation across much of North America, Europe, and western Asia. Unlike most terns, they rarely nest on open sand or gravel, instead favoring vegetated wetlands.

Migration

After breeding, Black Terns move to coastal and marine habitats, migrating to winter along the coasts of Central and South America (New World populations) or the coasts of Africa (Old World populations). Wetland drainage and habitat degradation have caused declines in some breeding regions.

Behavior

Black Terns forage in flight, dipping down to snatch insects from the water surface or the air, and also take small fish and aquatic invertebrates. Their flight is light, agile, and erratic compared with the steadier flight of larger terns.

Voice

Calls include a sharp "kik" or "kip" and a more strident "kreea," given especially around the breeding colony.

Nesting and breeding

Pairs nest in loose colonies on floating mats of vegetation, muskrat houses, or emergent plants over shallow water. They typically lay two to three eggs, and the semi-precocial chicks are tended by both parents until fledging.