As a group, the storm-petrels are unlikely to be confused with any other bird species in our region, except perhaps a wayward swallow. Within this group, however, species identification can be moderately to extremely complicated. Within B.C., the Ashy Storm-Petrel is most similar to the Leach’s Storm-Petrel, which is also a primarily dark species. However, the Ashy Storm-Petrel lacks the bold white rump patch of Leach’s Storm-Petrel, which should immediately distinguish the two species under most circumstances. It also has a longer and more deeply-forked tail than Leach’s and is overall greyer (dark sooty-grey in Ashy, dark blackish-brown in Leach’s). Some populations of Leach’s Storm-Petrel breeding off northern Baja California, and which range north into California and could potentially occur as a vagrant into B.C., lack the white rump patch of more northerly-breeding Leach’s and are therefore much more similar to Ashy Storm-Petrel. For these individuals it will be necessary to rely on more subtle structural and plumage differences between the species. The other species of storm-petrel occurring in B.C., Fork-tailed Storm-Petrel, is overall much paler grey with a bold black “M” across the upperwings that is formed by the blackish primaries and the blackish bar across the upperwing coverts. In addition, the Fork-tailed Storm-Petrel shows a distinct dark patch through the eye that is not shown on the much darker sooty-grey head of the Ashy Storm-Petrel.
Finally, a species that occurs in California and could potentially range north into B.C. as a vagrant, the Black Storm-Petrel, is larger and longer-winged than Ashy Storm-Petrel, and is much darker and blacker overall. Like Ashy, however, it has a solidly dark rump and could potentially be a source of confusion. The tail of Black Storm-Petrel is not quite as deeply forked as in Ashy Storm-Petrel. Other all-dark storm-petrels that occur in the Pacific Ocean are extremely unlikely to occur in B.C. and their identification and separation from Ashy Storm-Petrel is not discussed here.
| This species generally calls only at night near its breeding colonies, and does not typically vocalize at sea other than occasional sharp clicks that are given when individuals pass each other in flight. Source: Ainley (1995) |
This species is a vagrant to British Columbia ana does not breed.
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The Ashy Storm-Petrel feeds primarily at night, and observations of daytime feeding are relatively rare. It feeds on a variety of small fish, invertebrates (young squid and octopus, crustaceans, etc.), and zooplankton that occur at the surface of the water. When feeding, this species picks food items delicately from the surface, both from flight and while sitting on the water, using its bill to tear chunks off of larger pieces of food. It sometimes occurs in association with fishing vessels where it searches out food particles from the detritus and offal that are thrown overboard. Where common, it often occurs in moderate-sized flocks, often in association with other species of storm-petrel. The vagrants to B.C., however, have not been seen in association with other species.
Source: Ainley (1995)
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