Hydrobates cheimomnestes
The Ainley's Storm Petrel (Hydrobates cheimomnestes) is a small, enigmatic seabird of the eastern Pacific, distinguished by its dark, sooty-brown plumage, a prominent white rump patch, and a subtly forked tail. Averaging 18-20 cm in length with a wingspan of approximately 45 cm and weighing 40-50 grams, it shares a general appearance with other storm petrels but possesses specific vocalizations and a unique breeding phenology. Recently recognized as a distinct species in 2021, it was previous...
This is a strictly pelagic species, inhabiting the open ocean for most of its life. It breeds exclusively on remote, offshore islands, nesting in burrows or rock crevices close to sea level.
Primarily feeds on small marine invertebrates like copepods and amphipods, small fish, and squid, usually picked from the ocean surface; they are also opportunistic scavengers of oily carrion or offal.
Ainley's Storm Petrels exhibit a fascinating dichotomy in their daily activity: strictly nocturnal at their breeding colonies to avoid predation, yet diurnal while foraging at sea. Their foraging strategy involves distinctive 'foot-pattering' on the ocean surface, where they hover or skim to snat...
The Ainley's Storm Petrel has a highly restricted breeding range, nesting exclusively on a few of the California Channel Islands, primarily Santa Barbara Island, San Miguel Island, and San Clemente Island, within the United States. Following the breeding season, individuals disperse widely across...
Data Deficient
- Its scientific name, *cheimomnestes*, literally means 'winter nester', a direct reference to its highly unusual breeding season. - Ainley's Storm Petrel was only recognized as a distinct species in 2021, after decades of being considered a population of Leach's Storm Petrel. - This species bree...