Ashy Storm Petrel - Distribution, Status, and Threats

Distribution, Status, and Threats

Ashy Storm Petrel breeds on 17 islands in the northeast Pacific, principally off the coast of California, but including a few sites off the coast of northwestern Mexico. Half the world's population nests on the Farallon Islands near San Francisco. Other breeding islands include the 8 Channel Islands of California and a small population on Mexico's Coronados. Outside of the breeding season it is believed to be more widely distributed, foraging on the California Current, but it undertakes no large migration and doesn't range as far as other species of storm-petrel. In the early fall large flocks can be seen in Monterey Bay. The birds do not range inland any significant distance except when storm-blown; for example a record for San Mateo County, California was considered "unusual" by an experienced naturalist.

The world population is estimated to be around 10,000 birds, 8,000 of them breeders, the Farallon population having declined by one third between 1972 and 1992. The Ashy Storm Petrel is designated as a species of conservation concern in California. It is threatened by Western Gull and Burrowing Owl predation, illumination from fishing boats, introduced predators such as rats and feral cats, and pollution. Most of the islands that it breeds on are covered by some degree of protection.

Global warming and climate change could have a profound impact on the Ashy-Storm petrel. Future changes to coastal California waters due to global warming could result in warmer, less productive waters, which would mean there would be less food available for the petrels. In addition, ocean acidification may result in a decline of crustacean prey species due to the effects that excess CO₂ will have on the animals’ shells. Sea-level rise will also threaten certain nesting sites that are located too close to the water.