Widely distributed and common over much of East and Central Africa. Rare in southern and western Cape Province. Absent from the drier areas. Probably migratory as individuals suddenly appear where not seen before.
Sexes are alike, female slightly larger, but size very variable.
The immature bird has a black stripe through the eye, a black crown and white underparts with the back oily brown. Seen as individuals or in groups and, when not breeding, congregate in flocks of many hundreds - a wonderful sight. Frequently chase one-another in short dashes or in low flight while calling loudly. Dives and swims when necessary and a strong flier, carrying its long toes trailing out behind. After landing, raises its wings above its head.