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BC Conservation Data Centre: Species Summary

Hydrobates homochroa
Ashy Storm-petrel

Scientific Name: Hydrobates homochroa (Coues, 1864)
Scientific Name Synonyms: Oceanodroma homochroa
English Name: Ashy Storm-petrel
Classification / Taxonomy
Scientific Name - Concept Reference: American Ornithologists' Union (AOU). 1998. Check-list of North American birds. Seventh edition. American Ornithologists' Union, Washington, D.C. [as modified by subsequent supplements and corrections published in The Auk]. Also available online:
Classification Level: Species
Taxonomy Comments: The genus Oceanodroma has been merged with Hydrobates, given that Oceanodroma is paraphyletic with respect to Hydrobates. Hydrobates has the priority (Chesser, Burns, Cicero et. al. 2019).
Species Group: Vertebrate Animal
Species Code: B-ASPE
Kingdom Phylum Class Order Family
Animalia Craniata Aves Procellariiformes Hydrobatidae
Conservation Status / Legal Designation
Global Status: G2 (Jun 2015)
Provincial Status: SNA (Oct 2008)
BC List: Accidental
Provincial FRPA list:   
Provincial Wildlife Act:
SARA Schedule:
General Status Canada:
Migratory Bird Convention Act: Y
Ecology & Life History
General Description:
Global Reproduction Comments: On the Farallon Islands, the eggs of this colonial breeder are laid primarily from late April to mid-July, but laying may extend into September (Ainley 1995). Individual females produce a single egg that is incubated alternately by both adults for 42-59 days; incubation change-over occurs at night. Fledging occurs at an age of 72-199 days (mean 84 days) (Ainley 1995). Age of first breeding is unknown. The closely related Leach's storm-petrel (Oceanodroma leucorhoa) begins breeding at an average age of five years (Huntington et al. 1996).Pairs are presumed to breed every year once they breed initially (Ainley 1995).
Migration Characteristics:
(Global / Provincial)
    Local Migrant:
    Distant Migrant:
    Within Borders Migrant:
N / N
Y / N
N / N
na / N
Global Migration Comments: Individuals move up to several hundred kilometers between nesting islands and marine foraging areas (Adams and Takekawa 2008).
(Type / Subtype / Dependence)
Global Habitat Comments: Ashy storm-petrels are pelagic and spend most of their time over the continental slope of the eastern Pacific Ocean. Nesting occurs on islands; eggs are deposited in natural cavities under rocks or in existing burrows, and sometimes in similar artificial sites (Spendelow and Patton 1988), from near seal level to the highest interior parts of the nesting islands (Ainley 1995). Nesting areas are either devoid of predatory mammals (e.g., offshore rocks) or in sites that are basically inaccessible to them (e.g., steep slopes, sea caves).
Food Habits: Invertivore: Adult, Immature
Piscivore: Adult, Immature
Global Food Habits Comments: Diet includes small cephalopods, krill and other crustaceans, and fishes (especially those that rise to the sea surface at night) (Ainley 1995).
Global Phenology: Diurnal: Adult, Immature
Global Phenology Comments: Feeding likely occurs mostly at night or twilight (Ainley 1995). Nocturnal activity also occurs during breeding period (incubation change-overs).
Provincial Phenology:
(1st half of month/
2nd half of month)
Colonial Breeder: Y
Length(cm)/width(cm)/Weight(g): 20/ / 37
Elevation (m) (min / max): Global: 
Endemic: N
Global Range Comment: Nesting occurs on islands off the coast of California and northern Baja California, including Bird Rocks and Double Point Rocks in Marin County, South Farallon Islands, Hurricane Point south of Monterey, Channel Islands (Prince Island and Castle Rock off San Miguel Island, Santa Cruz Island and offshore rocks, Santa Barbara Island and associated Sutil Island and Shag Rock, and Seal Cove Rock off San Clemente Island), and Los Coronados Islands (Carter et al. 1992, 2006, 2008; Ainley 1995; McChesney et al. 2000; Center for Biological Diversity 2007). Small numbers may nest on Anacapa Island, Santa Catalina Island, mainland San Miguel Island, mainland San Clemente Island, offshore rocks in Van Damme Cove in Mendocino County, on Chimney Rock in Marin County, mainland at Vandenberg Air Force Base, and Todos Santos Island (Carter et al. 1992, 2006, 2008; Nur et al. 1999; Brown et al. 2003). Nonbreeding range is confined primarily to the continental slope from Cape Mendocino, California, to central Baja California (Ainley 1995, Adams and Takekawa 2008).
Authors / Contributors
Global Information Author: Hammerson, G.
Last Updated: Oct 28, 2008
Provincial Information Author:
Last Updated:
References and Related Literature
Ainley, D. 1995. Ashy Storm-Petrel (Oceanodroma homochroa), The Birds of North America Online (A. Poole, editor). Ithaca: Cornell Lab of Ornithology; Retrieved from the Birds of North America Online.
American Ornithologists' Union (AOU). 1983. Check-list of North American Birds, 6th edition. Allen Press, Inc., Lawrence, Kansas. 877 pp.
Carter, M., C. Hunter, D. Pashley, and D. Petit. 1998. The Watch List. Bird Conservation, Summer 1998:10.
Carter, M., G. Fenwick, C. Hunter, D. Pashley, D. Petit, J. Price, and J. Trapp. 1996. Watchlist 1996: For the future. Field Notes 50(3):238-240.
Harrison, C. 1978. A Field Guide to the Nests, Eggs and Nestlings of North American Birds. Collins, Cleveland, Ohio.
International Union for Conservation of Nature and Natural Resources (IUCN). 2000. 2000 IUCN Red list of threatened species. International Union for Conservation of Nature and Natural Resources, Species Survival Commission, Cambridge, U.K.
Naveen, R. 1981. Storm-petrels of the world: an introductory guide to their field identification. Birding 13(6):216-29.
Sowls, A.L., A.R. DeGange, J.W. Nelson and G.S. Lester. 1980. Catalog of California seabird colonies. U.S. Dept. Interior, Fish and Wildlife Service, Office of Biological Services, Coastal Ecosystems Project, Washington, DC. 4 p.
Spendelow, J. A. and S. R. Patton. 1988. National Atlas of Coastal Waterbird Colonies in the Contiguous United States: 1976-1982. U.S. Fish and Wildlife Service, Biological Report 88(5). x + 326 pp.
Terres, J. K. 1980. The Audubon Society encyclopedia of North American birds. Alfred A. Knopf, New York.
Warham, J. 1991 (also listed as 1990). The petrels: their ecology and breeding systems. Academic Press. viii + 440 pp.

Please visit the website Conservation Status Ranks for definitions of the data fields used in this summary report.

Suggested Citation:

B.C. Conservation Data Centre. 2008. Species Summary: Hydrobates homochroa. B.C. Minist. of Environment. Available: (accessed Sep 16, 2021).