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
Calonectris the Early Pliocene and "Calonectris wingatei" from the Middle Pleistocene, have also been described from fossils. "Calonectris kurodai", another fossil from the Middle Miocene Calvert Formation of Chesapeake Bay is named after the Japanese ornithologist Nagahisa Kuroda. Calonectris Calonectris is a genus of seabirds. The genus name comes from Ancient Greek "kalos", "good" and "nectris", "swimmer". The genus comprises three large shearwaters. There are two other shearwater genera. "Puffinus", which comprises about twenty small to medium-sized shearwaters, and "Procellaria "with another four large species. The latter are usually named as "petrels", although they are thought to be more closely related