Least Storm-Petrel
Least Storm-Petrel
Hydrobates microsoma
At a Glance
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.
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
Least Concern
Habitat
Open Ocean
Region
California
Behavior
Direct Flight, Erratic
Range & Identification
Migration & Range Maps
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.
Description
6" (15 cm). The smallest storm-petrel. Tiny and all black, with relatively short, wedge-shaped tail. Wingbeats are deep and rather fast.
Size
About the size of a Robin, About the size of a Sparrow
Color
Black, Brown
Wing Shape
Long, Narrow, Pointed, Tapered
Tail Shape
Pointed, Rounded, Wedge-shaped
Songs and Calls
Twittering and squeaking notes at nesting colonies.
Call Pattern
Flat
Call Type
Rattle, Raucous, Scream
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.
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Behavior
Eggs
One. White. Incubation probably by both sexes.
Young
Probably both parents feed young.
Feeding Behavior
forages mostly by fluttering low over water and taking items from surface. Seldom sits on water to feed.
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.
Climate Vulnerability
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.