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Broad-Billed Prion | Pachyptila vittata
Breedbekprion | Prión Piquiancho
The Broad-Billed Prion is the largest prion, with a heavy head and a strikingly broad, dark bill with which it filters plankton from the water. It breeds on Tristan da Cunha and Gough and reaches the waters off the Cape in the austral winter.
Voice
Silent at sea. At the breeding sites a cooing, crowing kuk-koo-kuk from the burrows at night.
Recording: David Boyle — CC BY-NC-SA 4.0 · shortened to the first 60 s, mono · xeno-canto
Identification
About 28 cm, a bulky prion with a large, angular head, a steep forehead and a very broad bill, bowed out at the sides and largely blackish; the comb-like lamellae are sometimes visible when the bill is closed. The upperparts are darker blue-grey than in other prions, with a black M across the wings. The head is dark, with a dark eye-stripe, a narrow white supercilium and a grey half-collar on the side of the breast. The underparts are white and the tail has a narrow black terminal band. The flight is somewhat slower and less twisting than in smaller prions.
Confusion species
Salvin's Prion (Pachyptila salvini) is smaller, with a narrower, bluer bill and a less angular head; the differences are subtle at sea and partly overlap. Antarctic Prion (Pachyptila desolata) has an even narrower blue bill and a rounder head. Blue Petrel (Halobaena caerulea) has a white tail tip and a dark cap.
Habitat
Cool ocean, mainly in the subtropical and subantarctic zones, in winter north over the cold Benguela Current. It feeds by 'hydroplaning' with the bill through the water and filtering out copepods and other zooplankton. It breeds in burrows and crevices on oceanic islands.
Where the bird is most at home, classified by the vegetation units of southern Africa.
Range and movements
In the region a winter visitor far off the Western Cape, in some years also off the Southern Cape and in small numbers north off Namibia; after storms sometimes washed up on beaches in numbers. It breeds in the South Atlantic on Tristan da Cunha and Gough, and also on islands off New Zealand, including the Chatham Islands.
How and when to look
Winter pelagic trips out of Cape Town offer the best chance, especially after a prolonged north-westerly gale. A prion that looks notably large, dark and big-headed deserves a side-on photograph of the bill. On the tideline the broad bill identifies the species at once.
Conservation status
Not threatened; the world population numbers millions of pairs. On Gough introduced house mice, which eat chicks alive, are a serious threat; an eradication attempt is under way.
Scientific name
Pachyptila vittata | (Forster, 1777)
Forster described the species in 1777 as Procellaria vittata; because it was later moved to another genus, the author and year stand in brackets. The genus Pachyptila was introduced in 1811 by Illiger. Pachyptila comes from the Greek pakhus, 'dense, thick', and ptilon, 'feather' — for the dense, soft plumage of the prions. vittata is Latin for 'banded, striped', from vitta, 'ribbon' — probably for the dark M-shaped band across the wings. The specimen the first description was based on came from Tristan da Cunha.