The Black Tern (Chlidonias niger) is probably sootier looking than this species, if anything this species could be better named the “pied tern” as it is as bright white as it is black. Essentially the upperparts are black, and the underparts are white, with a bright white forehead and backward pointing white supercilia. Formerly in the genus Sterna, now various tropical pelagic terns and the Aleutian Tern, have been found to be more closely related to each other, and only distantly related to true Sterna terns. This is based on molecular data, and this is why now they are classified into the genus Onychoprion. There are two tropical Onychoprion in much of the New World, the Sooty and the Bridled Tern, and often the two are found together. The Sooty is the more black and white species, while the bridled has a black cap that contrasts with a paler grayish-brown back. Both breed colonially in tropical islands and islets, often in very large numbers. In the non-breeding season they disappear into the pelagic realm of the oceans. The Atlantic Sooty Terns appear to largely go and winter in offshore regions off Africa; where the Pacific birds go is unclear. When offshore they are dependent on large predatory fish, such as tuna. The predatory fish bring small bait fish close to the surface of the water, allowing access to these fish from the diving terns. Experienced fishermen have known for years that to find the good fish, you find the groups of foraging terns such as the Sooty.