About Pterodroma externa (Salvin, 1875)
The Juan Fernández petrel, with the scientific name Pterodroma externa (Salvin, 1875), is a large gadfly petrel. It measures 43 cm (17 in) long, has a wingspan of 95–97 cm (37–38 in), and reaches a mass of 500 g (1.1 lb). Its upperparts are dark brownish-grey, with a black M-shaped marking across its extended wings. The underparts are white, and the underside of the wing is edged in black. It has a white face with a black cap that extends below the eyes. Its feet are yellow with dark brown tips, and its bill is black with a hooked tip, holding the tubular nostrils unique to the order Procellariiformes. During the breeding season, these petrels forage in waters surrounding Isla Alejandro Selkirk and Isla Robinson Crusoe (both part of Chile’s Juan Fernández Archipelago), as well as off coastal Chile. They often form flocks with pink-footed shearwaters and other seabirds. During the non-breeding season, they forage in equatorial currents and counter-currents, reaching as far north as the Hawaiian Islands. The species has been recorded as a vagrant in Australia, the Chatham Islands of New Zealand, Fiji, and the United States (Arizona and Oregon). Juan Fernández petrels breed only on a single Chilean island, Isla Alejandro Selkirk. The breeding population was estimated at 1 million pairs in 1985–1986, and the global population may total up to 3–5 million individual birds. The species is threatened at its nesting sites by predation from introduced species (cats and rats), and to a lesser extent by habitat loss caused by introduced herbivorous goats. The IUCN Red List classifies this species as Vulnerable, due to its restricted endemic range and threats from introduced predators.
