Rare and poorly known seabird found in the Pacific Ocean well off the coast of Mexico. It breeds in the winter on small islets near Guadalupe Island, located 160 miles from the mainland, and disperses southward during other times of the year. Plumage is dark gray with a notched tail, white rump patch, and pale stripes on the upperwing. The rump patch is variable in extent, and on some birds may be split down the middle by gray feathers. Identification is extremely difficult due to its similarity with other species, especially Townsend’s Storm-Petrel and Leach’s Storm-Petrel. Remains at sea when not breeding; flies erratically and often patters the ocean with its feet.