[4][5] A genetic analysis using mitochondrial DNA has shown that the closest living relative is the Galápagos shearwater (Puffinus subalaris).

[7] The species closely resembles the sooty (Puffinus griseus) and short-tailed shearwaters (P. tenuirostris), but has dark brown underwings and is smaller.

The short tail of the Christmas shearwater does not appear blunt except when spread, but in flight usually tapers to a point, enhanced by the feet which protrude beyond the tail-tip.

The two species share a similar morphology and colouration, but the bulbous head and rather thin long bill – typical for shearwaters – distinguish P. nativitatis from the slim-headed thick-billed Fiji petrel.

Outside of the breeding season it ranges across the Pacific, having been recorded off the coast of Mexico and Guatemala in the east, and Bonin Islands in the west.

As mentioned above, it does not only have the dramatic stiff-winged "shearing" (dynamic soaring) flight technique which gave the shearwaters their common name.