Tuesday 18 June
Stejneger’s petrel (Pterodroma longirostris)
Stejneger’s petrel fact file
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Stejneger’s petrel description
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).
- Petrel de Más Afuera.
Stejneger’s petrel biology
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).Top
Stejneger’s petrel range
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).Top
Stejneger’s petrel habitat
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).Top
Stejneger’s petrel status
Classified as Vulnerable (VU) on the IUCN Red List 2006 (1).Top
Stejneger’s petrel threats
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).Top
Stejneger’s petrel conservation
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).Top
Find out more
For further information see:
- Brooke, M. (2004) Albatrosses and Petrels across the World. Oxford University Press, Oxford.
- Juan Fernández Islands Conservancy:
For more information on this and other bird species please see:
- BirdLife International:
Authenticated (11/06/07) by Dr Peter Hodum, Juan Fernández Islands Conservancy.
- A species or taxonomic group that is only found in one particular country or geographic area.
- The act of searching for food.
- Inhabiting the open oceans.
- IUCN Red List (January, 2007)
- del Hoyo, J., Elliott, A. and Sargatal, J. (1992) Handbook of the Birds of the World. Vol. 1: Ostrich to Ducks. Lynx Edicions, Barcelona.
- Antarctic Connection (May, 2007)
- Birdlife International (May, 2007)
- Brooke, M. (2004) Albatrosses and Petrels across the World. Oxford University Press, Oxford.
- Burnie, D. (2001) Animal. Dorling Kindersley, London.
- Hodum, P. (2007) Pers. comm.
- Juan Fernández Islands Conservancy 2003 Annual Report (2003)
- Save the Albatross (May, 2007)
- Juan Fernández Islands Conservancy (May, 2007)
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