Stejneger's Petrel

The breeding season for Stejneger's petrel begins in November with the birds nesting in colonies, often with the Juan Fernández petrel (Pterodroma externa). Burrows, 0.5 - 1 meter long, are excavated in the soil by males using their bill and feet. Breeding females lay a single egg each season, with the peak laying period occurring in late November to early December (7). Peak hatching occurs during the first half of February, and fledging occurs in early to mid May (2) (8). When provisioning chicks, adults embark on foraging trips, typically lasting for four to ten days. Thus the chicks typically go for several days at a time without being fed (7). During the breeding season the diet appears to be dominated by squid, with some fish (7). Like all other petrels and closely related albatrosses, Stejneger's petrel has a special digestive system consisting of an upper and lower stomach. Oil is produced from the petrel's diet and stored in the upper stomach. This concentrated, calorie-rich oil acts as a constant source of energy as small amounts trickle into the lower stomach to be absorbed. It is also an efficient means of transporting energy back to the breeding colony, as the oil weighs less than unprocessed prey, where it can be regurgitated to feed the chicks (7) (9). After multiple days spent foraging at sea, the adults return to the colony, calling noisily. Breeding birds return straight to their burrows, whilst non-breeding birds may spend several hours on the surface, sleeping, interacting, and exploring other burrows. Whilst birds are on the surface of the colony, they are most at risk from predation (8). However, they have a form of defence in the sticky and foul-smelling oil produced by the stomach. If threatened, adults and chicks can eject large quantities of the oil, which sticks onto the fur or feathers of a predator. Not only does this make the predator smell awful, the coated fur or feathers lose their insulating and waterproofing properties, which can be fatal (9).

The Juan Fernández Islands were designated a Chilean National Park in 1935, a UNESCO International Biosphere Reserve in 1977 and nominated for World Heritage status in 1995. IUCN also identified the archipelago as one of the world's 12 most threatened National Parks. The Juan Fernández Islands Conservancy was established to protect the ecosystems of the islands through research, conservation action and environmental education, in collaboration with local residents (10). As a result of outreach and education programmes, the fishing community is now very aware of the petrel colony and is actively taking steps to protect the island's two petrel species, thus human disturbance has actually decreased (7). The Juan Fernández Islands Conservancy is conducting a long-term research program focused on four pelagic seabirds, one of which is Stejneger's petrel, investigating their basic ecology, breeding biology and conservation threats as well as developing priorities for long-term conservation of the species (10). Between 1998 and 2003, the Juan Fernández Islands-Dutch Cooperative Project also implemented control programs for several exotic plant species and goats on the island. However, given that the projects were of limited duration and were only control programs, the Conservancy believes that they were only temporary measures and that complete eradication of feral cats, rats, mice and goats are necessary to protect the future of these seabirds (8).

This small petrel belongs to a group of oceanic birds that return to land only to breed. The name petrel comes from the Latin petrellus, which literally means 'Little Peter', after the Apostle who is said to have walked on water with Christ, and refers to the way they patter on, or hover just above, the ocean's surface (3). Stejneger's petrel has dark grey upperparts, marked with a black 'M' shape. The forehead, crown and hindneck are also dark grey, which extends slightly onto the white throat and breast, like a collar. The underwing is white, with a black tip, a narrow black trailing edge and a noticeable black “comma” marking from the outer part of the leading edge of the wing, extending partly into the middle of the underwing (2) (4). The name longirostris reflects its relatively long bill compared to other small petrels (5). The bill possesses a pair of tubular nostrils, positioned on either side. This is a feature unique to the order Procellariiformes, which enables these birds to have an exceptionally acute sense of smell, used to locate food and nest sites in the dark (6). Its voice is a rapid ti-ti-ti call (5).

Like other petrels, this is a marine and highly pelagic bird. On its single breeding island it occurs in dense fern forest and grasslands on slopes and ridges, generally at elevations between 850 and 1,100 meters (2) (4).

Stejneger's petrel is endemic to a single breeding island; Alejandro Selkirk Island in the Juan Fernández Islands, Chile (2). When not breeding, they migrate across the equator, passing southern California and Hawaii, to the north-west Pacific off Japan (4); however, the exact migratory route and range of the wintering grounds is virtually unknown (7).

Classified as Vulnerable (VU) on the IUCN Red List 2006 (1).

Stejneger's petrel breeds only on one island, and findings suggest that the entire population breeds in a single extended colony on a single ridgeline. Thus any disturbance focused on that area, whether chronic, like predation, or catastrophic, like a wildfire, could wipe out the entire breeding colony for the species (7). Predation by feral cats, rats, and mice on this species has been documented (7), and may be causing numbers to decline. Stejneger's petrel is more vulnerable than the Juan Fernández petrel due to its smaller size, making it the preferred prey for cats (2) (4). Feral goats are also present in and around the colonies, and impact the petrel by damaging vegetation and destroying suitable breeding habitat for these burrowing birds (4) (7). Another threat is attraction to lights in the small town, particularly during bad weather. Birds are drawn in by the lights, become disorientated, and can collide with buildings and light poles, or land on the ground where they are vulnerable to cats and dogs in the town (7). To date, no at-sea threats have been documented for the species, but interactions with fisheries and ingestion of plastics may have impacts on the population (7).

Stejneger's petrel (Pterodroma longirostris) is a species of seabird and a member of the gadfly petrels. The bird is 26–31 cm in size, with a 53–66 cm wingspan.

This species is highly pelagic, rarely approaching land, except to nest and rear young. It occurs in the Pacific Ocean, nesting in the Cerro de Los Inocentes mountain of the Juan Fernández Islands off Chile. It is a transequatorial migrant, finding its way to subtropical waters off Japan before returning to its nesting sites. It has been reported well off the west coast of the United States.

Stejneger's petrel nests in burrows. It prefers slopes and ridges in areas of dense fern forests. The population of this bird is decreasing due to introduced cats on its breeding islands. It is considered a vulnerable species because of its restricted breeding range.

The common name commemorates the Norwegian ornithologist Leonhard Hess Stejneger.