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Trindade Petrel | Pterodroma arminjoniana
Arminjon-stormvogel | Petrel de Trinidad
The Trindade Petrel breeds on Trindade and the Martim Vaz islands in the South Atlantic, off Brazil, with a small population on Round Island off Mauritius. Outside the breeding season birds wander through the Atlantic as far as the Gulf Stream off the south-eastern United States. In the Caribbean it is a very rare vagrant at sea.
Voice
Almost silent at sea. Calls are known only from the breeding colonies.
Recording: Kathryn Hodder — CC BY-NC-SA 4.0 · converted to mono · xeno-canto
Identification
35–39 cm. A medium-sized petrel with long, narrow wings, a fairly long, wedge-shaped tail and a short, heavy, black bill. There are pale, dark and intermediate forms. Dark birds are almost uniformly dark grey-brown. Pale birds have a dark head, upperparts and breast band and a white belly. In all forms the underwing shows a pale patch at the base of the primaries. The flight is fast and swinging, in high arcs.
Confusion species
Sooty Shearwater Ardenna grisea has a long, slender bill, a silvery panel along the centre of the underwing and a flatter flight with quicker beats. Dark jaegers such as Pomarine Jaeger Stercorarius pomarinus have broader wings, a white flash on the primaries also on the upperwing and an active flight. Black-capped Petrel Pterodroma hasitata has a white hindneck, a white rump and white underparts without a breast band.
Habitat
Open ocean over deep, warm water, far offshore. It eats mainly squid and fish, taken at the surface. It breeds on ledges, rocky slopes and ridges of oceanic islands.
Where the bird is most at home, classified by the vegetation types of the Caribbean.
Range and movements
Only a few records at sea are known from the Caribbean, including off the Bahamas and Guadeloupe; it has not been reported regularly from any island. There is no range map. North of the region it is seen regularly in the Gulf Stream, and after hurricanes birds sometimes end up far north, as in Nova Scotia in 2022. Beyond the region it breeds on Trindade and the Martim Vaz islands and on Round Island off Mauritius.
How and when to look
A chance exists almost only on pelagic trips over deep water. Any dark or two-toned petrel with a short, thick bill needs photographs of the underwing; they are essential for an accepted record.
Conservation status
Vulnerable. The breeding range is very small. On Trindade the vegetation was badly damaged by introduced goats, pigs and cats; it is recovering since the goats were removed. Introduced predators remain a risk. No regular presence in the Caribbean.
Scientific name
Pterodroma arminjoniana | (Giglioli & Salvadori, 1869)
Giglioli & Salvadori described the species in 1869 as Aestrelata Arminjoniana; because it was later moved to another genus, the author and year stand in brackets. The genus Pterodroma was introduced in 1856 by Bonaparte. Pterodroma is Greek, from pteron 'wing' and dromos 'runner', after the fast, sweeping flight. arminjoniana honours the Italian naval officer Vittorio Arminjon, captain of the ship on the voyage during which the first specimen was collected. The specimen the first description was based on came from Trindade, Brazil.