stejneger's petrel Pterodroma longirostris

Medium-sized, elegant seabird of the deep Pacific Ocean, rare in Japanese waters. Grayish above, white below, with dark “M” pattern in upperparts. White forehead extensive; dark gray crown stands out against lighter gray back and often terminated by a sharp white “notch” of plumage. Underwing mostly white, with only small black marks at the “wrists,” unlike many other gadfly petrels, and tip of tail extensively black, unlike rather similar Cook’s and Masatierra Petrels.