These small petrels do not breed in the New Zealand region but on Isla Noir off the coast of Chile, the Falkland Islands, the Crozet Islands, and the Kerguelen Island. However, the birds from the large colonies on the Kerguelen Island in the Indian Ocean disperse after the breeding season eastwards and many, usually young birds, reach New Zealand waters in winter. Some become beach wrecked every winter, July through August, around New Zealand's coasts but occasionally, in 1974 and 1986, and now again in 2011, they are wrecked in large numbers.
On New Island, one of the West Faulkner Islands, a population of around two million, possibly representing almost 30% of the species, pairs of thin-billed prions nest despite the presence of introduced ship rats, house mice and feral cats. Prions are extremely numerous on New Island, but only during the breeding season. On the other hand, rats and cats seem to be relatively scarce probably due to the scarcity of winter food resources. Tussock, which in other subantarctic islands is an important source of food and shelter for rats, is very scarce on New Island. Furthermore, there are no winter-nesting seabirds on New Island that might provide a complementary source of food. In spring and summer, predators that survive the winter are apparently swamped by an over-abundance of potential prey.
The prions comprise six species of true prion in the genus Pachyptila and the closely related Blue Petrel. Often known in the past as whalebirds, three species have large bills filled with lamellae that they use to filter plankton somewhat as baleen whales do, though the old name derives from their association with whales, not their bills.
— Greytown, 2011
Other common names: —
narrow-billed prion, slender-billed prion
26 cm., 145 g., sexes alike, blue-grey head and back, a white throat and belly, a black M-shaped mark across their wings, slender bill, legs blue, very narrow black tip to tail.
Where to find: —
Found in NZ waters through the winter.
Illustration description: —
Heather, B., & Robertson, H., Field Guide to the Birds of New Zealand, 2000.
Polar Biol (2007) 30:391–394, Can thin-billed prions Pachyptila belcheri breed successfully on an island with introduced rats, mice and cats? The case of New Island, Falkland Islands P. Catry,M. C. Silva, S. MacKay, A. Campos, J. Masello, P. Quillfeldt, I. J. Strange
Page date & version: —
Monday, 2 June 2014; ver2009v1