Trindade petrel  (Pterodroma arminjoniana)

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

A highly oceanic bird, the Trindade petrel (Pterodroma arminjoniana) roams across three of the world’s oceans (4). The name petrel derives from St. Peter who “walked on the waves”, and describes the petrel’s hovering flight, in which it sometimes skims the water surface when searching for food (4).

The Trindade petrel comes in three distinct morphs (5). The dark morph is a beautiful dark chocolate brown with a paler throat, and usually has white-tipped flight feathers on the underwing. Its legs and feet are black (5) (6). The pale morph is more variable in appearance, but is usually brown, with a paler underwing and throat. (6). It has a dark brown tail, pink legs and feet, and may have a grey-brown upperparts with a darker “M” shape across the back and wings (7). The intermediate morph largely resembles darker pale morphs, but its appearance can vary significantly, making it difficult to identify (6).

Male and female Trindade petrels are similar in appearance, but the young are covered in a light, grey fluffy plumage. A distinguishing feature of the Pterodroma genus is the wide, black, hooked bill of these species (2).

The Trindade petrel is found across the Atlantic, Indian and Pacific Oceans, coming to land only to breed. Breeding takes place mainly on the Trindade and Martin Vaz islands off the coast of Brazil (1).

Breeding colonies of the Trindade petrel have previously been found on Mauritius (8) and on Réunion Island (7). Mauritius currently has a colony of birds of the Pterodroma genus that is thought to be the Trindade Petrel, but this has yet to be verified (2).

The Trindade petrel is an oceanic bird, spending much of its time on or above the sea (5). When returning to the tropical Trindade and the Martin Vaz islands to breed, the birds tend to nest very high up on the islands, making them difficult to study (9).

This species burrows slightly to make sheltered but basic nests on the ground or rock surface (7). These burrows are made of not much more than rocks and soil (8).

The Trindade petrel lives in dense breeding colonies (7) and breeds throughout the year (9), with the largest number of eggs laid between October and April (2).

The Trindade petrel lays a single egg (11), and, as is typical for the Pterodroma genus, the male and female take turns at incubation (10). Following hatching, the adults may continue to provide some food for the chick until it is up to 75 days old (7).

The Trindade petrel preys on small fish of around 10 centimetres in length, searching for prey by skimming the water surface (12). Being so close to the water surface also allows this petrel to remain stable in flight even in very stormy conditions (4).

The call of the Trindade petrel is a quick and repetitive “ki” or “keh”, used frequently in the mornings. This is normally associated with a playful aerial chase between a male and female (8).

Population estimates of the Trindade petrel have been vastly reduced in recent years, with its population estimated to number just 1,130 individuals in 2008, down from 15,000 in 2004 (2).

Its highly restricted breeding range makes this species vulnerable to chance events. As a ground nesting species, the Trindade petrel is susceptible to predation by introduced species and disturbance by human activities (2). Its breeding areas were previously shared with introduced pigs, rats, cats and goats (7), eliminating low altitude populations and forcing the Trindade petrel to nest on inaccessible cliff sites on higher ground (2).

The proposed building of a naval airbase on Trindade and the construction of experimental wind turbines on the island pose future threats to the Trindade petrel. However, there are few threats known to its populations on the uninhabited Martin Vaz Islands (2).

In a large-scale conservation project, pigs and cats were eradicated from the island of Trindade by 1970, and goats by 2005. Work is currently going on to restore the forest habitats on the island, which have been largely reduced by the goats and by fires. Proposals have also been made to keep Trindade mainly as a natural reserve, and to prevent any construction on the island before an assessment of its possible impact on wildlife (2).

It is also hoped that biologists will be able to determine if the unidentified Pterodroma colony on Round Island, Mauritius, is in fact the Trindade Petrel (2).

Find out more about the Trindade petrel and its conservation:

• Birdlife International - Trindade petrel:
  http://www.birdlife.org/datazone/speciesfactsheet.php?id=3894
• Neves, T., Olmos, F., Peppes, F. and Mohr, L.V. (2006) National Plan of Action for the Conservation of Albatrosses and Petrels. Brazilian Institute of Environment and Natural Renewable Resources (IBAMA), Brasília. Available at:
  ftp://ftp.fao.org/FI/DOCUMENT/IPOAS/national/brazil/NPOA-Seabirds_Brazil.pdf

More information on the conservation of albatrosses and petrels:

• Agreement on the Conservation of Albatrosses and Petrels (ACAP):
  http://www.acap.aq/