This species has occurred as a rare vagrant to the United States, Italy, and Spain.

Recent evidence suggests the South American and African populations may represent two separate cryptic species.

The black tips to the primary wing feathers have conspicuous white "mirrors".

[2] It is locally abundant, breeding in large colonies in reedbeds and marshes; it lays two or three eggs in a nest, which can be on the ground or floating.

Although it is predominantly coastal or estuarine, it is not a pelagic species, and is rarely seen at sea far from land.