Wilson's Storm-Petrel vs Swinhoe's Storm-Petrel

Wilson's Storm-Petrel and Swinhoe's Storm-Petrel are both small, dark seabirds often seen fluttering low over the ocean. The most reliable field mark is the white rump of Wilson's Storm-Petrel, which Swinhoe's lacks. Both species have similar flight patterns, but Swinhoe's is slightly larger and more uniformly dark.

1. Look for the white rump: Wilson's Storm-Petrel has a prominent white rump, absent in Swinhoe's. 2. Size and structure: Swinhoe's is slightly larger and more robust. 3. Flight behavior: Both species may flutter close to the water, but Wilson's often shows foot-dipping behavior. 4. Habitat: Consider the location; Swinhoe's is more likely in northern pelagic zones.

Swinhoe's Storm-Petrel is slightly larger than Wilson's Storm-Petrel.

Wilson's Storm-Petrel has a distinctive white rump patch, while Swinhoe's Storm-Petrel is uniformly dark with no white rump.

Both species exhibit a fluttering flight close to the water surface, often pattering on the water with their feet. Wilson's Storm-Petrel is known for its foot-dipping behavior while foraging.

Wilson's Storm-Petrel is a generalist, found in a wide range of pelagic environments, whereas Swinhoe's Storm-Petrel is typically found in the northern hemisphere's pelagic zones.