This species account is dedicated in honor of Chuck Huntington, director of the Bowdoin Scientific Station on Kent Island (1953–1989), and Bill Ellison, a member of the Cornell Lab of Ornithology's Administrative Board.
Leach's Storm-Petrel, also known as Leach's Petrel or Mother Cary's Chicken, is the most widespread procellariiform breeding in the Northern Hemisphere. More than 6 million pairs nest in burrows or crevices on Atlantic islands from Norway to Massachusetts and on Pacific islands from Baja California to Hokkaido, Japan. Outside the long nesting season, these seabirds disperse widely in the Atlantic and Pacific oceans, well away from land and mainly in the tropics. Millions more nonbreeding individuals, mostly immatures, remain at sea year-round, although many of them visit colonies during the nesting season, often covering vast distances. Small and dark and not usually gregarious or attracted to ships, this species is inconspicuous at sea. Much work remains to determine the nonbreeding distributions of these populations.
Populations breeding on Guadalupe Island off Baja California are now considered separate species; the summer-breeding Townsend’s Storm-Petrel (O. socorroensis) and winter-breeding Ainley’s Storm-Petrel (O. cheimomnestes). The smaller, dark-rumped Swinhoe's Storm-Petrel (Oceanodroma monorhis), nesting off Japan, Korea, China, and Russia, is so similar that it had been considered a subspecies of Leach's Storm-Petrel; the two are appropriately considered a superspecies.
Like all storm-petrels (as far as it is known), this species feeds on zooplankton and nekton at the surface of the sea, pecking at individual organisms while hovering, resting briefly on the surface, or, rarely, pattering with wings partly spread. Nesting in burrows dug on wooded or treeless islands or in crevices among rocks, individuals return faithfully each year to their colony. While individuals fly to and from their subterranean nests over their colonies at night, they utter a loud Chatter Call; in the nest they produce a Purring Call, often as a duet, for many minutes at a time. Like all procellariiforms, this species is long-lived and lays only one egg per year. Both sexes incubate and feed the young, which develops slowly and becomes very fat before slimming down to flying mass in the fall.