Ardenna bulleri

Buller's Shearwater

Family: Procellariidae · Class: Aves · Order: Procellariiformes

Buller's Shearwater (Ardenna bulleri) is a medium-sized seabird belonging to the family Procellariidae. Adults measure 46 to 51 cm (18 to 20 inches) in length with a wingspan of 97 to 99 cm (38 to 39 inches). The species exhibits distinctive plumage with dark gray-brown upperparts forming a contrasting 'M' pattern across the wings when viewed from above. The underparts are predominantly white with dark margins along the wing edges. The bill is long, slender, and dark gray, while the legs and feet are pink to flesh-colored. The species can be distinguished from similar shearwaters by its clean white underparts and the prominent dark 'M' pattern on the dorsal wing surface. Buller's Shearwater breeds exclusively on islands off New Zealand, particularly the Poor Knights Islands and surrounding offshore islets. During the non-breeding season, the species undertakes extensive trans-Pacific migrations, reaching the waters off California, Oregon, and Washington. In California waters, Buller's Shearwater is most commonly observed from July through October, with peak abundance occurring in August and September. The species typically remains in offshore pelagic waters, generally beyond the continental shelf edge. The species inhabits open ocean environments, preferring areas with upwelling currents that concentrate marine prey. Off California, Buller's Shearwater is associated with the California Current system, particularly areas where cold, nutrient-rich water supports high concentrations of small schooling fish and squid. The species is typically observed over waters deeper than 200 meters (656 feet) but may venture closer to shore during periods of strong upwelling or when following productive water masses. Buller's Shearwater feeds primarily through surface seizing and shallow plunge-diving, capturing small fish, squid, and crustaceans. The diet consists largely of anchovies, sardines, juvenile rockfish, and market squid (Doryteuthis opalescens). The species often feeds in association with other seabirds, marine mammals, and commercial fishing vessels. Breeding occurs from October through April in New Zealand, with birds constructing burrow nests in soil or under rock crevices. Females lay a single white egg, and both parents participate in incubation duties lasting approximately 51 days. Chicks fledge after 97 to 106 days. Currently, Buller's Shearwater lacks formal federal or state conservation status in California, as it is considered a non-breeding visitor to the region. However, the species faces several threats throughout its range, including habitat degradation at breeding sites, predation by introduced mammals on nesting islands, plastic pollution, and potential impacts from climate change on prey availability. The New Zealand population is estimated at approximately 2.5 million individuals according to BirdLife International. Conservation efforts in New Zealand focus on predator control at breeding colonies and habitat restoration on nesting islands. In California waters, the species benefits from marine protected areas and regulations governing commercial fishing operations that may impact seabird feeding areas.

Data from The California Species Project — 14,000+ California species with verified data from CNPS, CDFW, USFWS, and more.