A small, slender petrel with long, narrow wings and a long tail. It is entirely dark brown except for diagonal buff-colored bars on the upper wings. The flight is usually low over the water, with fewer high arcs than other petrels. Nests on small islets off Kauai, Oahu, and Maui, and on most of the Northwestern Hawaiian Islands. Commonly seen offshore from boats and sometimes from shore. The call, heard only at breeding colonies, is a soft bark.