Wilson's Storm-Petrel vs Black-bellied Storm-Petrel

In short

Wilson's Storm-Petrel and Black-bellied Storm-Petrel can be distinguished by their plumage and behavior. The most reliable field mark is the bold black central belly stripe on the Black-bellied Storm-Petrel, though it can be hard to see against dark water. Wilson's Storm-Petrel lacks this stripe and has a more uniform dark belly.

Identification tips

• Look for the black central belly stripe on Black-bellied Storm-Petrel, though it may be difficult to see against dark water.
• Note the longer legs of Black-bellied Storm-Petrel which extend beyond the tail in flight.
• Observe the foraging behavior: Wilson's Storm-Petrel dips feet, while Black-bellied skips off waves.
• Consider habitat: Wilson's is more of a generalist, while Black-bellied prefers colder waters.

Size

Both species are small storm-petrels, but Black-bellied Storm-Petrel has longer legs that project beyond the tail in flight.

Plumage

Wilson's Storm-Petrel has a dark belly and underparts, while Black-bellied Storm-Petrel is characterized by a bold black central belly stripe and darker upperparts. Both have dark upperwings and tails, but the Black-bellied has a pale carpal bar and white wing linings.

Behaviour

Wilson's Storm-Petrel forages by dipping its feet into the water, while Black-bellied Storm-Petrel skips off waves using one leg in an asymmetrical manner.

Habitat

Wilson's Storm-Petrel is a generalist, often found in a variety of pelagic environments, while Black-bellied Storm-Petrel prefers colder, sub-Antarctic waters.