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
Audubon's shearwater homogeneous north-western Indian Ocean range, but not in the ecologically more diverse and by far larger Pacific range of "dichrous". These unresolved problems notwithstanding, this clade – possibly including the preceding one – has been proposed to constitute a separate species, the tropical shearwater or Baillon's shearwater, "Puffinus bailloni". These taxa could not be included in the most recent studies due to lack of material. The case of "gunax" seems fairly straightforward – as certainly as this can possibly be said in the absence of new data, it belongs to the "bailloni" clade either as a distinct subspecies, or, more