Ashy Storm-Petrel
Ashy Storm-Petrel
Hydrobates homochroa
At a Glance
A small seabird with a limited range, breeding only on offshore islands from central California to northern Baja, and dispersing only short distances at sea. Flies low over the waves with relatively shallow wingbeats. Of the various all-dark storm-petrels on the west coast, this one is medium-sized and slightly paler than the others.
All bird guide text and rangemaps adapted from by Kenn Kaufman© 1996, used by permission of Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Category
Gull-like Birds, Storm-Petrels
IUCN Status
Endangered
Habitat
Coasts and Shorelines, Open Ocean
Region
California
Behavior
Direct Flight, Rapid Wingbeats
Population
5.100
Range & Identification
Migration & Range Maps
In fall, a high percentage of total population may concentrate on Monterey Bay, central California. Some are present in California waters at all seasons, but at northern end of range the species is least numerous in early winter; apparently some move a short distance south to waters off western Mexico. Unlike many storm-petrels, performs no long-distance migration.
Description
7 1/2" (19 cm). All dark but not as black as other species of storm-petrels; has brown or gray tinge. Wingbeats shallower than those of Black Storm-Petrel, wings raised only to about horizontal.
Size
About the size of a Robin, About the size of a Sparrow
Color
Black, Gray
Wing Shape
Pointed, Tapered
Tail Shape
Forked, Notched
Songs and Calls
Twittering and squeaking notes given near nest burrow.
Call Pattern
Flat
Call Type
Rattle, Raucous, Scream
Habitat
Open ocean. During summer, favors relatively cool waters of the California Current, feeding mainly just off the edge of the continental shelf. In fall, concentrates where deep waters of Monterey Submarine Canyon come relatively near shore in Monterey Bay. Nests on rocky islands with abundant crevices for nest sites.
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Behavior
Eggs
One. White or with faint reddish-brown dots. Incubation is by both sexes, averages about 45 days.
Young
probably both parents feed young, by regurgitation. Young leaves nest and goes to sea on average about 84 days after hatching.
Feeding Behavior
Forages mostly by hovering or skimming low over water and taking items from surface; also will sit on water to feed. Probably forages mostly at dusk and at night.
Diet
Probably mostly crustaceans and small fish. Diet is not well known. Includes small fish, and crustaceans such as euphausiids. Once reported to feed heavily on the larval stage of spiny lobster off southern California.
Nesting
Breeds in colonies on offshore islands. Active at colonies only at night, arriving there just after dark and departing before first light. Some adults may visit colony every month of year. At Farallon Islands off central California, nesting is not synchronized; egg-laying may occur any time late April to mid-July, rarely to September. Before eggs are laid, both members of pair may spend time in nest chambers, giving trilling and twittering songs. Nest: site is in natural cavity or crevice under rock piles, under driftwood, or in old burrow of other species; usually no nest lining added.
Climate Vulnerability
Conservation Status
Reasonably common in its limited range. Well protected at the largest and best-known colony (estimated 2000 pairs) at the South Farallon Islands. Would be quite vulnerable to an oil spill or other disaster on Monterey Bay in fall, when most of world's population is present there.