WatchList Species Account for Ashy Storm-Petrel
(Oceanodroma homochroa)

Qualifies for the list as a Red List Species


Ashy Storm-Petrel
Photo: Glen Tepke

Using natural cavities primarily on talus slopes, the Ashy Storm-Petrel nests on 17 rocky islands off the coast of California, from Southeast Farallon in the north, to San Clemente in the south, and on one Mexican island, Los Coronados. Its non-breeding range is the continental shelf from northern California to central Baja California, Mexico.


At present its population size is estimated to be between 5,200-10,000 individuals, but between 1972 and 1999 a 42% decline was documented on the Farallon Islands, where about 50% of the world population breeds. Although the cause is not definitively known, it may be related in part to natural oceanic fluctuations. Among the threats on the Farallons is the expanding number of Western Gulls. In addition, introduced grasses are invading breeding habitat there after the introduced rabbits were removed, and introduced mice feed on petrel eggs.Among the existing and potential threats are ingestion by the birds of floating plastics, pollution from oil and pesticides, the illumination of colonies during night-time squid fishing that may increase predation rates, and disturbance by researchers.


Among proposed solutions to increase the population on the Farallons to pre-1980 levels are non-lethal gull hazing, the use of artificial nest boxes, the removal of mice, and the eradication of non-native grasses. The threat from introduced species on other breeding islands should be assessed and eradication measures employed, if needed.