Buller’s shearwater  (Puffinus bulleri)

Classified as Vulnerable (VU) on the IUCN Red List 2006 (1).

Buller’s shearwater has been described as flying with a grace and economy like no other, characterised by longer gliding motions and less wing flapping, each bird arcing and tilting seemingly without effort (3) (4). In flight, a dark bar on the pale grey wings and lower back forms an unmistakable and arresting ‘M’-shaped pattern from above (3) (4), easily distinguishing this shearwater from any other (2). Upperparts are otherwise brownish-grey, while underparts are white (2). The grey, wedge-shaped tail is broadly tipped in black, the long, slender bill is bluish grey with a darker tip, and the legs and feet are pink (5) (6).

Amazingly, the estimated population of some 2,500,000 birds breeds on just one small island group (Poor Knights Islands) off New Zealand, where it is restricted to two main islands, Aorangi and Tawhiti Rahi, and five other islets and stacks. In the non-breeding season, these masses migrate to the north Pacific Ocean, from Japan to North America, and are occasionally found off South America (6).

This marine, pelagic bird comes to shore only to breed (2), nesting in burrows, rock-crevices and ledges, often under dense vegetation (6).

Buller’s shearwaters return to the Poor Knights Islands in mid-September to court females and clean out their burrows before breeding (7). Nesting occurs in large, dense colonies (5), with egg-laying beginning in October (2) (7). The single white egg is incubated by both sexes for about 51 days, and most chicks fledge at around 90 days (5). The following April to late May sees the colonies departing once more for the north Pacific (5) (7).

The diet consists of krill, small fish, squid and jellyfish (6), and birds have only recently started to scavenge fishing boat scraps (5).

Buller’s shearwater was previously caught in drift-nets in the north Pacific, with an estimated 4,000 birds killed annually, and may still be at risk from set-nets (6) (8). Longline fishing, trawling operations, and hand-and-reel lines may also pose a threat, although little documented evidence of this exists (6) (8). Furthermore, this bird’s very limited breeding range renders it extremely vulnerable to the effects of accidentally introduced predators, disease, storms and other catastrophes (6) (8). Indeed, the dense colonies nesting on the Poor Knights Islands were once devastated by introduced pigs. Thankfully, after the eradication of the pigs the shearwaters recovered spectacularly and now have a healthy, growing population, but the potential risk to a bird with such a small breeding range nevertheless remains (4).

There was a massive increase in the population after the eradication of feral pigs from Aorangi in 1936, with recolonising populations probably coming from the nearby predator-free island, Tawhiti Rahi (6). The large population is thought to be continuing to grow on the Poor Knights Islands, a protected, now predator-free nature reserve, and if it succeeds in expanding its range, this species may be downlisted to Near Threatened on the IUCN Red List (6) (7).

View information on this species at the UNEP World Conservation Monitoring Centre.

For more information on Buller’s shearwater see:

• BirdLife International:
  http://www.birdlife.org/datazone/species/index.html?action=SpcHTMDetails.asp&sid=3929&m=0