Grey-backed Storm Petrel
Garrodia nereis
Grey-backed storm petrel is a small bird, 21-44 g in weight with a 39–40 cm wingspan. Like others in its family it is dark grey overall with a black head and belly, but it can be distinguished from other storm-petrels in its range by its light grey rump compared to the white rump on others. The Grey-backed petrel has a pale back, black legs, a square tail and a white belly.
ID text from Wikipedia, CC BY-SA 4.0
White-faced Storm Petrel
Pelagodroma marina
Commonly, the white-faced storm petrel is 19 to 21 centimetres (7.5 to 8.3 in) in length with a 41 to 44 centimetres (16 to 17 in) wingspan and 40 to 70 grams body mass. The key characteristics of this species include dark bill, tarsi, toes and claws. It has a pale brown to grey back, rump and wings with black flight feathers. It is white below, unlike other north Atlantic petrels, and has a white face with a black eye mask like a phalarope. Its distinctive grey-brown dorsal side plumage makes it one of the easier petrels to identify at sea from a distance.
ID text from Wikipedia, CC BY-SA 4.0
Where you might meet both
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Play today's Daily BirdPhotos and recordings are credited to their authors under the licence shown. Full profiles: Grey-backed Storm Petrel and White-faced Storm Petrel.