Black-capped Petrel is a distinctive gadfly petrel with a clearly defined black cap separated from the dark mantle by a white collar and with conspicuous white uppertail coverts that form a broad U shape. Discrete variation among individuals, mostly in the extent of dark "cap," suggests that Black-capped Petrel might be a complex of multiple species with different nesting seasons; more research is needed to determine the taxonomic status of these different types. Although Black-capped Petrel can be seen readily off the coast of the southeastern United States, particularly in Gulf Stream waters from North Carolina to Florida, the global population is in fact quite small and faces threats both at the Caribbean nesting colonies and at sea.