rybák bělokřídlý Chlidonias leucopterus

Buoyant “river tern” with dramatically different breeding and non-breeding plumages. Breeding adult is wildly conspicuous in flight, with contrasting black-and-white plumage; at rest note white shoulders contrasting with black body. Non-breeding and younger birds are white with gray patches and black “earmuffs.” In areas of overlap, juvenile told from Black Tern by dark back contrasting with lighter upperwings and white rump and by black marking above the shoulder. Non-breeding Whiskered Tern can be similar, but has a faded, patchy dark crown instead of earmuffs. Commonly found in flocks around rivers, lakes, and wetlands, where it picks food from surface instead of splash-diving; generally not as closely associated with saltwater as many typical terns.