Bucephala clangula
Small, stocky diving duck with short bill, big triangular head and yellow eyes (dark in juveniles). Male: dark metallic green head and white patch at base of bill. Black back and tail. Neck, breast and underparts white. Female with brown head, white collar and pale underparts. White, square wing panels and dark underwing in both sexes.
Male display sound a dry nasal disyllabic "Ka-weerr". First note introductory and second longer and descending. Usually accompanied by back-throwing head motion. Female: dry harsh "aahrrrr aahrrrr aahrrrr ". Wings make a characteristic whistling sound.
Wikipedia: map (se also Xeno-canto below)
Birdlife ecology
