Wilson's Storm-Petrel vs Leach's Storm-Petrel

Wilson's Storm-Petrel and Leach's Storm-Petrel are both small, dark seabirds often seen fluttering over the ocean. The most reliable field mark is the tail shape: Wilson's has a square tail, while Leach's has a distinctly forked tail. Observing flight style can also help; Wilson's tends to have a more fluttering flight compared to the bounding flight of Leach's.

1. Tail shape: Look for the square tail of Wilson's versus the forked tail of Leach's. 2. Flight style: Wilson's has a fluttering flight, while Leach's is more bounding. 3. Behavior: Wilson's often 'walks' on water, a behavior less common in Leach's. 4. Habitat proximity: Wilson's may be seen closer to shore. 5. Vocalization: Listen for Leach's purring call at breeding sites.

Both species are similar in size, but Leach's Storm-Petrel is slightly larger with a longer wingspan.

Wilson's Storm-Petrel has a uniform dark brown plumage with a white rump, while Leach's Storm-Petrel also has a white rump but may show a paler band across the upper wing in some lights.

Wilson's Storm-Petrel often 'walks' on water, pattering with its feet, while Leach's Storm-Petrel has a more bounding flight and does not exhibit this behavior as frequently.

Both species are pelagic and found over open ocean, but Wilson's Storm-Petrel is more of a generalist, often seen closer to shore compared to Leach's.

Vocalizations are rarely heard at sea, but Leach's Storm-Petrel has a distinctive purring call at breeding colonies, while Wilson's is generally silent.