Bird of the Week, November 2, 2012

Ashy Storm-Petrel


Ashy Storm-Petrel by Kirk Zufelt

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The Ashy Storm-Petrel weighs just over an ounce and is eight inches long with a forked tail. Its dark, smoky-gray plumage blends in perfectly with its foggy surroundings at sea.


This petrel lives and feeds in the California Current, a major cold water system that churns from north to south along the West Coast of the United States, forming the foundation of an astonishingly rich ecosystem that ranges from microscopic plankton to blue whales.


Over half of this species' population occurs on the South Farallon Islands off central California. Like other storm-petrels, Ashy Storm-Petrels fly to and from their nesting colonies at night; but unlike their cousins, they do not travel far from their colonies after breeding.


Major threats to the Ashy Storm-Petrel include predation by Burrowing Owls, the population of which has soared due to the introduction of non-native mice on the islands, and predation by gulls, whose population has risen due to the increase of garbage on the mainland. As a result, the storm-petrel population on the Farallons declined by 40% between 1972 and 1992. These birds are also very sensitive to disturbance; nesting colonies can easily be disrupted by recreational kayakers and fishermen. Petrels foraging at sea are further at risk from ingesting floating plastics, and from oil and pesticide pollution.


Recommended conservation measures include eradicating introduced predators from nesting islands and investigating effects of artificial lights on predation and breeding success.




Photo: Kirk Zufelt; Range Map, NatureServe