Endangered seabird that nests only in Galápagos. Outside the breeding season, it disperses over the eastern Pacific and usually stays far from land. Note distinctive black-and-white pattern on underwing, mostly white underparts, and dark upperparts that extend down through its face to sides of neck; no other seabird found in and near Galápagos shares these features. When seen from above, it appears all dark except for some white around the base of the bill. Almost always encountered at sea, since it travels to and from its highland nesting sites only at night.