Region

Eastern Pacific Ocean

Typical Environment

Breeds on offshore islets from southern California through Baja California and disperses widely over the tropical to subtropical eastern Pacific, often ranging south to Central America and beyond. At sea it occurs far from shore over deep water but can concentrate over productive upwelling zones and along shelf edges. It is strictly pelagic outside the breeding season and rarely approaches land. Breeding sites are on rocky islands with crevices, talus, or burrows, and it attends colonies only at night for safety.

Altitude Range

Sea level to 100 m

Climate Zone

Subtropical

Temperament

pelagic and wary

Flight Pattern

buoyant with short rapid wingbeats interspersed with glides

Social Behavior

A colonial nester, it breeds in loose to dense colonies on offshore islands, laying a single egg in a crevice or burrow. Adults are largely nocturnal at colonies and show strong site fidelity, often returning to the same nest each year. Pairs are typically monogamous and share incubation and chick-rearing duties.

Migratory Pattern

Seasonal migrant

Song Description

Mostly silent at sea, but at colonies it gives low, chattering trills and purrs delivered at night from within crevices. Calls are soft and carry poorly, aiding in predator avoidance.

Diet

Feeds on small marine prey taken at or just below the surface, including euphausiid krill, copepods, fish eggs and larvae, and small squid. It will also scavenge oily scraps and occasionally follows ships or dolphins to exploit disturbed prey. Captures food by dipping, pattering with its feet on the surface, and snatching items in flight.

Preferred Environment

Most often forages over deep offshore waters and along productive fronts, slicks, and upwelling zones. It may aggregate where prey is concentrated by currents or where nocturnal prey rise toward the surface.