Audubon's shearwater underparts are white, as is the head below eye level. The iris is dark, the feet are dull pink with a black wash and black toenails, and the bill is grey, darker towards the tip, and with a pinkish hue. Males and females look alike. Immature birds do not have a distinct plumage, while the nestlings are covered with down feathers, grey above and whitish on the belly. It can be confused with the Manx shearwater ("P. puffinus"), which has white undertail coverts and in direct comparison a longer bill. Other similar-looking species are usually completely allopatric, though the largely
Bulweria "b" sequence analysis has proven them to be closely related to the shearwaters in the genus "Puffinus" and especially the "Procellaria" petrels. Bulweria Bulweria is a genus of seabirds in the family Procellariidae named after English naturalist James Bulwer. The genus has two extant species, Bulwer's petrel ("B. bulwerii") and Jouanin's petrel ("B. fallax"). A third species, the Olson's petrel ("Bulweria bifax"), became extinct in the early 16th century; it is known only from skeletal remains. Bulwer's Petrel ranges in the Atlantic, Indian and Pacific Oceans, whereas Joaunin's Petrel is confined to the northwestern Indian Ocean. Olson's Petrel is known