Endangered, small black-and-white shearwater, endemic to Mexico. Found around Socorro Island mainly from November to May, and rarely offshore between Jalisco and Oaxaca. It is usually found with feeding flocks of other shearwaters, boobies, and terns. Flight is fast and strong, wheeling fairly high in strong winds. Blackish above and white below with blackish undertail coverts, fairly long tail, and white patches or saddlebags that wrap up around the base of the tail. Similar species: Black-vented Shearwater is dark brownish above without the strong black cap of Townsend’s.