Photo: J. Hoffman/Vireo

Least Storm-Petrel

Oceanodroma microsoma

A tiny seabird, the smallest of the storm-petrels, no larger than a sparrow. It flies low over the waves with fast deep wingbeats, giving it a rather batlike look. Nests only on islands off western Mexico, but moves north irregularly into California waters in late summer, sometimes in large numbers. On the rare occasions when hurricanes off western Mexico turn inland, this species may be carried along; Hurricane Kathleen in 1976 deposited hundreds on the Salton Sea in southern California.
Conservation status Numbers probably stable, but overfishing and pollution of Gulf of California could have negative impact. Vulnerable to introduced predators (such as rats and cats) on some nesting islands.
Family Storm-Petrels
Habitat Open ocean. Favors warm waters; more likely to move north along California coast in years when water temperature is higher. Generally over continental shelf, and may occur closer to shore than some other storm-petrels, often being seen from shore in Mexico. Nests on rocky islands.
A tiny seabird, the smallest of the storm-petrels, no larger than a sparrow. It flies low over the waves with fast deep wingbeats, giving it a rather batlike look. Nests only on islands off western Mexico, but moves north irregularly into California waters in late summer, sometimes in large numbers. On the rare occasions when hurricanes off western Mexico turn inland, this species may be carried along; Hurricane Kathleen in 1976 deposited hundreds on the Salton Sea in southern California.
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Feeding Behavior

forages mostly by fluttering low over water and taking items from surface. Seldom sits on water to feed.


Eggs

One. White. Incubation probably by both sexes. Young: Probably both parents feed young.


Young

Probably both parents feed young.

Diet

probably tiny crustaceans and other very small marine life. Diet very poorly known; presumably feeds mainly on zooplankton (general term for tiny creatures floating in water). Once reported to feed on larval stages of spiny lobster.


Nesting

Nesting behavior poorly known. Breeds in colonies on islands off northwestern Mexico. At San Benito Island, many nests reported to have eggs during July. Active around nesting colonies only at night. Makes whirring calls from inside nest. Nest: Site is reported to be usually among piles of rocks, or in crevices in cliffs. Apparently not in burrows as in many other storm-petrels. Several pairs may nest close together if good sites are clustered. No nest built, egg laid on bare rock.

Illustration © David Allen Sibley.
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Text © Kenn Kaufman, adapted from
Lives of North American Birds

Migration

Moves north irregularly into California waters, mostly August and September. Numbers quite variable; sometimes hundreds recorded, occasionally none. In mid-autumn moves south along coast of Central America, commonly as far as Panama, a few as far as Peru.

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Migration

Moves north irregularly into California waters, mostly August and September. Numbers quite variable; sometimes hundreds recorded, occasionally none. In mid-autumn moves south along coast of Central America, commonly as far as Panama, a few as far as Peru.

Songs and Calls
Twittering and squeaking notes at nesting colonies.
Audio © Lang Elliott, Bob McGuire, Kevin Colver, Martyn Stewart and others.
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