Black-winged Petrel vs Buller's Shearwater

The Black-winged Petrel and Buller's Shearwater can be distinguished by their wing patterns and overall coloration. The Black-winged Petrel has a distinctive dark 'M' pattern on its upper wings, while Buller's Shearwater shows a more uniform gray back with a prominent white underwing. Both species are seabirds often seen in the Pacific, but their plumage and behavior offer clues for identification.

Look for the dark 'M' pattern on the wings of the Black-winged Petrel. Note the white underwing with a dark border in Buller's Shearwater. Consider size and association with other seabirds; Buller's is larger and more social. Check the back color: gray in Buller's versus more contrasting in the Black-winged Petrel.

Buller's Shearwater is generally larger than the Black-winged Petrel, with a more robust build.

The Black-winged Petrel features a dark 'M' pattern on its upper wings and a white belly, whereas Buller's Shearwater has a gray back, white underparts, and a distinctive white underwing with a dark border.

Buller's Shearwater often associates with other seabirds and follows trawlers, while the Black-winged Petrel is less likely to do so.

Both species are pelagic, but Buller's Shearwater breeds on islets off New Zealand and disperses widely across the Pacific, whereas the Black-winged Petrel is more restricted to subtropical and tropical waters.

Vocalizations are not a reliable field mark for distinguishing these species at sea.