Bonin Petrel

The Bonin petrel is a small gadfly petrel, 30 cm long with a wingspan of around 67 cm. It has a white head with a black cap and face markings; overall the head often has a scaled appearance. Its pale grey upperparts have darker primaries and wing coverts creating an "M" mark across the back. The underwing is white with dark edging and a patch at the carpal joint and across underwing coverts. The tail is dark grey, and the rest of the plumage is white, except for a dark half collar on the breast. Like the rest of the Pterodroma petrels the black bill is short and hooked. The legs and feet are pink with dark patches. The Bonin petrel is currently thought to be closely related to the mottled petrel and white-necked petrel in the subgenus Proaestrelata, based on a review of the whole genus Pterodroma looking at morphology, calls, breeding biology, diet and parasitic lice. Despite the species having two remote and separate breeding localities the species is monotypic and no subspecies are recognised.

After the breeding season both chicks and adults migrate northwards to the seas off Honshū and Sanriku in Japan. The timing of the migration is partly influenced by sea surface temperatures. Birds begin to disperse south and east again in August and begin to return to their breeding islands in September. During the breeding season birds feed in the waters surrounding breeding islands. The species has not been recorded in the east Pacific.