Atlantic petrel (Pterodroma incerta)
|Also known as:||hooded petrel, Schlegel's petrel|
|French:||Pétrel de Schlegel|
|Size||Length: 43 cm (2)|
Wingspan: 104 cm (3)
|Weight||c. 520 g (3)|
Classified as Endangered (EN) on the IUCN Red List (1).
The Atlantic petrel is one of the largest gadfly petrels (Pterodroma species), recognised by its striking white breast and abdomen that contrast with the uniformly black-brown plumage of the rest of the body (4). Particularly sharp colour demarcation exists from the brown upper breast to the white lower breast and belly (2). Sexes are alike (3).
The Atlantic petrel is a seabird predominantly restricted to the South Atlantic, ranging from the east coast of South America to the west coast of Africa (2). Until recently, a breeding population existed on Tristan da Cunha, but this is now believed to be extinct. Today, Gough Island is the only location where this species still breeds, with an estimated population of around 1.8 million pairs (2).
This bird nests in colonies on islands, but is otherwise pelagic (2). Nesting occurs in burrows dug in peaty soils in fern-bush vegetation from 50 to 300 metres above sea level on Gough, and at higher elevations on Tristan (2).
Atlantic petrels are winter breeders, returning to their colonies from February to March in order to mate (3). Single eggs are laid from June to July, with young hatching in August and September, and fledging in December and January (3) (5). The birds are exclusively nocturnal whilst on land (5). Chicks grow at a very slow rate, suggesting poor at-sea feeding conditions (5). The age of first breeding, breeding frequency and longevity are not yet known for this species (2).
Squid forms the bulk of the diet, although some crustaceans and fish will also be taken (2), and the Atlantic petrel possesses physical and behavioural adaptations geared towards catching such prey. The species’ towering flight style gives it a commanding field of view, useful in detecting widely dispersed prey (3). Furthermore, few other gadfly petrels in the region have such an elongated bill as this species, which is equipped with a strongly hooked tip, thought to be an adaptation to snatching live, slippery squid from the sea surface (3).
Although still common, the Atlantic petrel qualifies as Endangered because it has a very small breeding range, with the vast majority of the population on just one island (2). Such a limited range places the bird at risk from chance events such as natural disasters or the introduction of mammalian predators (2) (6). On Gough, predation by the introduced house mouse (Mus musculus) is having a severe effect on the Atlantic petrel’s breeding success, with just two percent of the chicks reaching fledging in 2007 (2). The large population of native southern skua (Catharacta antarctica) are also known to feed on seabirds including the Atlantic petrel (2).
On Tristan Island, where the Atlantic petrel was once common, it was likely to have been driven into decline by hunting, as it was formerly one of the few sources of food for the islanders during winter (6). Although this exploitation has abated, predation by introduced rats appears to have driven the island’s population to extinction (2).
Gough Island is both a Nature Reserve and World Heritage Site, and while this provides good protection from human disturbance, it does not offer the Gough bunting any protection from the mouse predation that is driving it towards extinction (2). A study of the mice conducted by The Royal Society for the Protection of Birds (RSPB) and funded by the UK government's Overseas Territories Environment Programme has shown that their eradication from the island is feasible. Unfortunately, however, until adequate funding is acquired this will not occur (7). Gough Island is widely recognised as having one of the most diverse bird colonies in the world, including four endangered species, and every effort should therefore be made to protect it and the rich biodiversity it hosts (8).
To learn more about the Atlantic petrel and its threats visit:
- BirdLife International:
- Cuthbert, R. (2004) Breeding biology of the Atlantic Petrel, Pterodroma incerta, and a population estimate of this and other burrowing petrels on Gough Island, South Atlantic Ocean. EMU, 104(3): 221 – 228.
Authenticated (15/12/08) by Ross Wanless and Andrea Angel, Percy Fitzpatrick Institute of African Ornithology.
- Nocturnal: active at night.
- Pelagic: inhabiting the open oceans.
IUCN Red List (November, 2011)