Buller's shearwater (''Ardenna bulleri'') is a Pacific species of seabird in the family Procellariidae; it is also known as the grey-backed shearwater or New Zealand shearwater. A member of the black-billed wedge-tailed ''Thyellodroma'' group, among the larger shearwaters of the genus '' Ardenna'', it forms a superspecies with the wedge-tailed shearwater (''A. pacificus'').

Description

Adults birds are in length, with a wingspan, and have been recorded to weigh . The upperside of Buller's shearwater is bluish grey. A blackish stripe runs from the tertiary remiges to the primary wing coverts. The primary remiges are blackish, also; the two black areas do not meet at the hand, however; the area between them is a rather light grey, and under bright light may appear almost white. With the bird facing upwards, the pattern gives the impression of a broken black "M", with light grey interspersing areas.Carboneras (1992) The underside is bright white; on the head the upperside's grey extends town to eye height and the white cheeks may shine up conspicuously, as in the smaller shearwaters of '' Puffinus sensu stricto''. The rectrices are blackish and the tail is wedge-shaped; the bill and irises are dark. Fledged juveniles already have the adult's colouration; the nestlings are covered in grey down feathers. Compared to other shearwaters, the species is unusually easy to identify at sea by its combination of considerable size and the distinctive, M-shaped banding pattern on its upperside while flying, uniquely among its genus and more akin to some

gadfly petrel The gadfly petrels or ''Pterodroma'' are a genus of about 35 species of petrels, part of the seabird order Procellariiformes. The gadfly petrels are named for their speedy weaving flight, as if evading gadflies ( horseflies). The flight action is ...

s (''Pterodroma''), the prions (''Pachyptila'') and their relative, the blue petrel (''Halobaena caerulea''). These are all much smaller birds, perhaps two-thirds in length and wingspan and less than half in bulk of Buller's shearwater.

Range and ecology

This species is pelagic like the other ''Ardenna'' shearwaters; it is a transequatorial migrant ranging across most of the Pacific Ocean outside the breeding season. Though it occurs in the

subarctic The subarctic zone is a region in the Northern Hemisphere immediately south of the true Arctic, north of humid continental regions and covering much of Alaska, Canada, Iceland, the north of Scandinavia, Siberia, and the Cairngorms. Generally, ...

waters off Kamchatka and the Aleutian Islands, it is not documented in the subantarctic Pacific; this apparent absence might simply be due to the lack of study opportunities in the vast islandless region south of the

Polynesian Triangle The Polynesian Triangle is a region of the Pacific Ocean with three island groups at its corners: Hawai‘i, Easter Island (''Rapa Nui'') and New Zealand (Aotearoa). It is often used as a simple way to define Polynesia. Outside the triangle, th ...

, however. It is fairly common well off the west coast of the United States during late summer and early autumn, and can generally be observed not far from land along the whole temperate and tropical coastlines of the

Americas The Americas, which are sometimes collectively called America, are a landmass comprising the totality of North and South America. The Americas make up most of the land in Earth's Western Hemisphere and comprise the New World. Along with th ...

. Its general absence from most of Melanesia and western Micronesia – where human settlement and sea traffic are considerable – is thus probably genuine; only isolated records, such as from the

Marianas The Mariana Islands (; also the Marianas; in Chamorro: ''Manislan Mariånas'') are a crescent-shaped archipelago comprising the summits of fifteen longitudinally oriented, mostly dormant volcanic mountains in the northwestern Pacific Ocean, betw ...

, Palau, and Yap, exist from west and southwest of the Marshall Islands. A vagrant bird was also recorded in the Atlantic once, offshore New Jersey, United States. Buller's shearwater feeds mainly on fish,

squid True squid are molluscs with an elongated soft body, large eyes, eight arms, and two tentacles in the superorder Decapodiformes, though many other molluscs within the broader Neocoleoidea are also called squid despite not strictly fitting t ...

, and crustaceans such as the krill '' Nyctiphanes australis''. It does occasionally follow ships, such as fishing trawlers, and may be part of a mixed-species feeding flock. Food is caught mainly at a head's length below the surface at most, the bird either picking it up with the bill only, often out of flight, or briefly inserting the entire head, usually while swimming. It neither dives out of flight very often, nor in a plunge off the water's surface. It is a colonial nester, breeding predominantly on Tawhiti Rahi and Aorangi, the main islands of the Poor Knights group offshore northern New Zealand. This bird nests in burrows, rock crevices, or under tree roots, preferring densely forested slopes. Buller's shearwater can also be found to breed in cracked-up rock on treeless

stack Stack may refer to: Places * Stack Island, an island game reserve in Bass Strait, south-eastern Australia, in Tasmania’s Hunter Island Group * Blue Stack Mountains, in Co. Donegal, Ireland People * Stack (surname) (including a list of people ...

s or cliffs, however, and most of the other colonies – on the smaller Poor Knights islands between the main islands and off the southeast of Aorangi – are of such a nature. A pair was observed to breed on the

Simmonds Islands The Simmonds Islands are a small group of uninhabited islands in the Far North District of the Northland Region of New Zealand. The islands lie about 1 km north of Granville Point, at the southern end of Henderson Bay. The group consists of tw ...

in 1980, but this seems to have been an isolated incident. The breeding season starts in October and lasts for almost half a year. A single egg is incubated for about 51 days, with the parents changing between incubation and feeding every 4 days or so. Time to fledging is not well known, but by analogy with Buller's shearwater's relatives assumed to be around 100 days. In the past, it was heavily used as a food source by the Māori, and on Aorangi it suffered massive predation by feral pigs. Its population had crashed to a low of just 100-200 pairs on Aorangi in the late 1930s. The pigs were removed from the island in 1936, and the shearwater population recovered, numbering 200,000 pairs again in the early 1980s to approach

carrying capacity The carrying capacity of an environment is the maximum population size of a biological species that can be sustained by that specific environment, given the food, habitat, water, and other resources available. The carrying capacity is defined as t ...

on the island at the end of the 20th century. At all times, however, the colonies at Tawhiti Rahi and on the smaller islets could supply birds for the resettlement of Aorangi, and Buller's shearwater was never considered threatened with

extinct Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...

ion in the foreseeable future. Indeed, it is a very abundant bird, with an estimated world population of 2.5 million birds. As it is not known to occur on any larger island in the region outside the Poor Knights Islands, it is classified as

vulnerable Vulnerable may refer to: General * Vulnerability * Vulnerability (computing) * Vulnerable adult * Vulnerable species Music Albums * ''Vulnerable'' (Marvin Gaye album), 1997 * ''Vulnerable'' (Tricky album), 2003 * ''Vulnerable'' (The Used album) ...

by the

IUCN The International Union for Conservation of Nature (IUCN; officially International Union for Conservation of Nature and Natural Resources) is an international organization working in the field of nature conservation and sustainable use of natu ...

: a single localized catastrophe could wipe the species out.Carboneras (1992), IUCN (2008)

References

External links

Buller's shearwater photos
*ARKive
images and movies of the Buller's shearwater ''(Puffinus bulleri)''New Zealand Birds Online
{{Taxonbar, from=Q27074602 Buller's shearwater Birds of New Zealand Birds of the Pacific Ocean Buller's shearwater Buller's shearwater

Description

Range and ecology

See also

References

Further reading

Further reading

External links