Fork-tailed storm-petrel Hydrobates furcatus

Unique among storm-petrels in having an entirely silvery-gray plumage. Aside from overall plumage color, look for contrasting dark underwings, dark mask around eye, and deeply forked tail. Breeds on offshore islands across the North Pacific, from Japan to California. Fairly common over cool water, often not far from shore. Found singly or in large flocks, often mixed with other storm-petrels.