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Cook's Petrel | Pterodroma cookii
Cooks stormvogel | Petrel de Cook | Grazina-de-cook
Cook's Petrel is a small, pale grey petrel that breeds in New Zealand and outside the breeding season crosses the Pacific to the Humboldt Current and further north. It stays far offshore and flies fast, in high arcs over the waves.
Voice
Silent at sea. In the colonies rapid, high calls at night.
Recording: Nathan El — CC BY-NC-SA 4.0 · xeno-canto
Identification
26 cm, a small, slender petrel with a short black bill and long, narrow wings. The upperparts are pale blue-grey, with a dark M across the wings and back; the tail is grey with a dark tip, and the outer tail feathers are paler. The crown and hindneck are pale grey, the forehead is white and a small blackish patch surrounds the eye. The underparts are white. The underwing is almost entirely white, with only a short dark bar at the carpal and a narrow dark edge to the wingtip. The sexes are alike.
Confusion species
Masatierra Petrel Pterodroma defilippiana is darker grey, with a larger, more prominent eye mask and a dark leading edge to the outer underwing. Slender-billed Prion Pachyptila belcheri has a white supercilium and flies low over the waves, without high arcs. Juan Fernandez Petrel Pterodroma externa has a similar pattern but is almost twice as large.
Habitat
Open ocean, especially far beyond the continental shelf. It feeds mainly on squid, small fish and crustaceans, picked from the surface in flight. It breeds in burrows in forested hill and mountain country on islands off New Zealand, mainly Hauturu (Little Barrier Island) and Whenua Hou (Codfish Island).
Where the bird is most at home, classified by the vegetation units of the Andes and the west coast.
Range and movements
In Peru on passage and as a non-breeding visitor far offshore, mainly in the austral winter; scarcer off Ecuador. Not in Bolivia. It does not breed in the guide area. Outside the guide area it breeds on islands off New Zealand; outside the breeding season it ranges over the eastern Pacific, from the Humboldt Current off Chile and Peru north to off Central America and California.
- Passage (Mar–Apr, Oct–Nov)
- dark = core range, pale = thinly spread
How and when to look
On pelagic trips far off Peru between April and October; the chance increases the further the boat travels beyond the continental shelf.
Conservation status
Vulnerable. The population has increased since cats and rats were removed from the main breeding islands, but the species breeds on very few islands and so remains sensitive to new predators and other disasters.
Scientific name
Pterodroma cookii | (Gray, 1843)
Gray described the species in 1843 as Procellaria Cookii; because it was later moved to another genus, the author and year stand in brackets. The genus Pterodroma was introduced in 1856 by Bonaparte. The genus name comes from Greek pteron, 'wing', and dromos, 'runner', after the fast flight. The species name honours James Cook (1728–1779), British explorer and Royal Navy captain. The specimen the first description was based on came from New Zealand.