Least Storm-petrel (Halocyptena microsoma)

Least Storm-petrel

Subspecies

Genus	Species	subspecies	Region	Range
Oceanodroma	microsoma		PO	ne

Genus

Storm-petrels are rather small and often dark colored tubenoses with a world wide distribution. All have fine black bills with very pronounced tubes. Storm Petrels are separated in two groups: the long legged, Southern Hemisphere birds subfamily Oceanitinae and the shorter legged species of more northern seas the subfamily Hydrobatinae. The first groups shows more morphological differences than the second. The genera are characterised on colour patterns, the condition of the nasal tubes, tail shape, structure of claws and proportions of the leg bones. The genus Halocyptena are Very small black petrels; bill weak, compressed and decirved; tail wedge shaped; wings rather long and pointed; tarsus rather short – slightly longer than mid-toe with claw and about half length of femur, claws narrow.

Physical charateristics

Very small. Only storm-petrel with a rounded or wedge-shaped tail. Flight erratic, batlike, close to water.

Listen to the sound of Least Storm-petrel

[audio:https://planetofbirds.com/MASTER/PROCELLARIIFORMES/Hydrobatidae/sounds/Least Storm-petrel.mp3]

Copyright remark: Most sounds derived from xeno-canto

wingspan min.:	31	cm	wingspan max.:	33	cm
size min.:	13	cm	size max.:	15	cm
incubation min.:	40	days	incubation max.:	45	days
fledging min.:	0	days	fledging max.:	0	days
broods:	1		eggs min.:	1
			eggs max.:	1

Range

Pacific Ocean : Northeast. This species breeds on islands in the Gulf of California and on the western coast of Baja California (Mexico). Its range stretches from California (USA) to as far south as Colombia and Ecuador.

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 storm-petrels, often being seen from shore in Mexico. Nests on rocky islands.

Reproduction

Nesting behavior very poorly known. Breeds in colonies on islands off northwestern Mexico. At San Benito Island, many nests reported to have eggs during July. Apparently active around nesting colonies only at night. Makes whirring calls from inside nest.

Nest: Site is reported to be usually in openings among piles of rocks, or in crevices in cliffs. Apparently not in burrows as in many other storm-petrels. Sev
eral pairs may nest close together if good sites are clustered. No nest built, egg laid on bare rock.
Clutch 1. White. Incubation probably by both sexes (as in other storm-petrels), but details unknown.
Young: Probably both parents feed young, as in other storm-petrels, but little is known of their development or age at first flight.

Feeding habits

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.
Behavior: Forages mostly by fluttering low over water and taking items from surface. Seldom sits on water to feed, and evidently does not dive underwater.

Conservation

This species has a very large range, and hence does not approach the thresholds for Vulnerable under the range size criterion (Extent of Occurrence <20,000 km2 combined with a declining or fluctuating range size, habitat extent/quality, or population size and a small number of locations or severe fragmentation). Despite the fact that the population trend appears to be decreasing, the decline is not believed to be sufficiently rapid to approach the thresholds for Vulnerable under the population trend criterion (>30% decline over ten years or three generations). The population size is very large, and hence does not approach the thresholds for Vulnerable under the population size criterion (<10,000 mature individuals with a continuing decline estimated to be >10% in ten years or three generations, or with a specified population structure). For these reasons the species is evaluated as Least Concern.

Migration

Breeds on islands off Baja California. A few range north in late summer and early fall to California. Migration: Moves north irregularly into California waters, mostly A
ugust 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.

Distribution map

Least Storm-petrel distribution range map

Planet of Birds