Leach's Storm-Petrel vs Townsend's Storm-Petrel

In short

Leach's Storm-Petrel and Townsend's Storm-Petrel are both small, dark seabirds with subtle differences in structure and plumage. The most reliable field mark is the tail shape: Leach's has a distinctly forked tail, while Townsend's tail is more square or slightly notched. Both species are challenging to differentiate at sea due to similar size and flight patterns.

Identification tips

1. Focus on tail shape: Leach's Storm-Petrel has a forked tail, while Townsend's Storm-Petrel has a square or slightly notched tail. 2. Look for the paler rump patch on Leach's, though this can be variable. 3. Be aware of the similar size and flight behavior, making tail shape the most reliable field mark. 4. Consider geographic location, as Townsend's may be more likely off southern California.

Size

Both species are similar in size, with no significant differences that are easily observable in the field.

Plumage

Leach's Storm-Petrel typically shows a paler rump patch compared to Townsend's, although this can be subtle and variable. Townsend's Storm-Petrel may appear slightly darker overall.

Behaviour

Both species exhibit similar flight patterns, characterized by erratic, fluttering flight with occasional glides. Observing tail shape during flight can be crucial for identification.

Habitat

Both species are pelagic and usually found far from land. Townsend's Storm-Petrel is known to disperse north and south at sea, particularly off the coast of southern California.

Voice

Vocalizations are not well-documented for either species in field conditions, and differences are subtle and not reliable for identification.