Black-winged Petrel vs Cook's Petrel

In short

Black-winged Petrel and Cook's Petrel are both small seabirds of the Procellariidae family, often seen in flight over open ocean. The most reliable field mark is the underwing pattern: Black-winged Petrel has a distinctive black edge to the underwing, while Cook's Petrel shows a more uniform pale underwing with less contrast.

Identification tips

1. Underwing pattern: Look for the black edge on Black-winged Petrel's underwing versus the pale, less contrasting underwing of Cook's Petrel. 2. Facial markings: Note the more distinct dark eye patch on Black-winged Petrel. 3. Size and shape: Cook's Petrel is slightly smaller and more slender. 4. Habitat context: Consider the oceanic region; Cook's Petrel is more common in subtropical waters.

Size

Both species are similar in size, but Cook's Petrel is slightly smaller and more slender.

Plumage

Black-winged Petrel has a grayish upper body with a black edge on the underwing and a white face with a dark eye patch. Cook's Petrel has a paler gray upper body, a more uniform pale underwing, and a less distinct facial pattern.

Behaviour

Both species exhibit similar flight patterns, characterized by graceful gliding and rapid wingbeats. They are often seen in mixed flocks with other petrels and shearwaters.

Habitat

Both species inhabit open ocean environments, but Cook's Petrel is more often associated with subtropical waters, whereas Black-winged Petrel can be found in both tropical and subtropical regions.

Voice

Vocalizations are not typically used for field identification as both species are silent at sea.