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Wedge-tailed Shearwater

Wedge-tailed Shearwater

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The Wedge-tailed Shearwater, Puffinus pacificus is a medium-large shearwater
Shearwaters are medium-sized long-winged seabirds. There are more than 30 species of shearwaters, a few larger ones in the genus Calonectris and many smaller species in the genus Puffinus...

 in the seabird
Seabirds are birds that have adapted to life within the marine environment. While seabirds vary greatly in lifestyle, behaviour and physiology, they often exhibit striking convergent evolution, as the same environmental problems and feeding niches have resulted in similar adaptations...

 family Procellariidae
The family Procellariidae is a group of seabirds that comprises the fulmarine petrels, the gadfly petrels, the prions, and the shearwaters. This family is part of the bird order Procellariiformes , which also includes the albatrosses, the storm-petrels, and the diving petrels.The procellariids are...

. It is one of the shearwater species that is sometimes referred to as a Muttonbird
Muttonbird, mutton-bird or mutton bird refer to seabirds – particularly certain large shearwaters – whose young are collected for food and other uses before they fledge ....

, like the Sooty Shearwater
Sooty Shearwater
The Sooty Shearwater is a medium-large shearwater in the seabird family Procellariidae. In New Zealand it is also known by its Māori name tītī and as "muttonbird", like its relatives the Wedge-tailed Shearwater and the Australian Short-tailed Shearwater The Sooty Shearwater (Puffinus griseus) is...

 of New Zealand
New Zealand
New Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...

 and the Short-tailed Shearwater
Short-tailed Shearwater
The Short-tailed Shearwater or Slender-billed Shearwater , also called Yolla or Moonbird, and commonly known as the muttonbird in Australia, is the most abundant seabird species in Australian waters, and is one of the few Australian native birds in which the chicks are commercially harvested...

 of Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...

. It ranges across from throughout the tropical
The tropics is a region of the Earth surrounding the Equator. It is limited in latitude by the Tropic of Cancer in the northern hemisphere at approximately  N and the Tropic of Capricorn in the southern hemisphere at  S; these latitudes correspond to the axial tilt of the Earth...

 Pacific and Indian Ocean
Indian Ocean
The Indian Ocean is the third largest of the world's oceanic divisions, covering approximately 20% of the water on the Earth's surface. It is bounded on the north by the Indian Subcontinent and Arabian Peninsula ; on the west by eastern Africa; on the east by Indochina, the Sunda Islands, and...

 roughly between latitude
In geography, the latitude of a location on the Earth is the angular distance of that location south or north of the Equator. The latitude is an angle, and is usually measured in degrees . The equator has a latitude of 0°, the North pole has a latitude of 90° north , and the South pole has a...

s 35°N and 35°S. It breeds in islands such as off Japan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...

, the Islas Revillagigedo, the Hawaiian Islands
Hawaiian Islands
The Hawaiian Islands are an archipelago of eight major islands, several atolls, numerous smaller islets, and undersea seamounts in the North Pacific Ocean, extending some 1,500 miles from the island of Hawaii in the south to northernmost Kure Atoll...

, the Seychelles
Seychelles , officially the Republic of Seychelles , is an island country spanning an archipelago of 115 islands in the Indian Ocean, some east of mainland Africa, northeast of the island of Madagascar....

 and off Western Australia
Western Australia
Western Australia is a state of Australia, occupying the entire western third of the Australian continent. It is bounded by the Indian Ocean to the north and west, the Great Australian Bight and Indian Ocean to the south, the Northern Territory to the north-east and South Australia to the south-east...



The Wedge-tailed Shearwater is the largest of the tropical shearwaters. There are two colour morphs of the species, dark and pale; the pale morphs predominate in the North Pacific
Pacific Ocean
The Pacific Ocean is the largest of the Earth's oceanic divisions. It extends from the Arctic in the north to the Southern Ocean in the south, bounded by Asia and Australia in the west, and the Americas in the east.At 165.2 million square kilometres in area, this largest division of the World...

, the dark morph elsewhere. However, both morphs exist in all populations, and bear no relation to sex or breeding condition. The pale morph has grey-brown plumage on the back, head and upperwing, and whiter plumage below. The darker morph has the same dark grey-brown plumage over the whole body. The species’ common name is derived from the large wedge-shaped tail, which may help the species glide. The bill is dark and legs are flesh coloured, with the legs set far back on the body (in common with the other shearwaters) as an adaptation for swimming.

This species is related to the pan-Pacific Buller's Shearwater
Buller's Shearwater
Buller's Shearwater is a Pacific species of seabird in the family Procellariidae; it is also known as the Grey-backed Shearwater or New Zealand Shearwater...

, which differs much in color pattern, but also has a wedgetail and a thin black bill (Austin, 1996; Austin et al., 2004). They make up the Thyellodroma group, a superspecies
A superspecies is a group of at least two more or less distinctive species with approximately parapatric distributions. Not all species complexes, whether cryptices or ring species are superspecies, and vice versa, but many are...

 in the large shearwaters of the proposed genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

 Ardenna (Penhallurick & Wink, 2004).


Wedge-tailed Shearwaters feed pelagically on fish
Fish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups...

, squid
Squid are cephalopods of the order Teuthida, which comprises around 300 species. Like all other cephalopods, squid have a distinct head, bilateral symmetry, a mantle, and arms. Squid, like cuttlefish, have eight arms arranged in pairs and two, usually longer, tentacles...

 and crustaceans. 66% of their diet is fish, of which the most commonly taken is goatfish
Goatfishes are tropical marine perciform fish of the family Mullidae. Seldom found in brackish waters, goatfish are most associated with the reefs of the Atlantic, Indian, and Pacific Oceans...

. It was thought that the species mostly took food from surface feeding, observations of feeding Wedge-tails suggested that contact-dipping, where birds flying close to the surface snatch prey from the water was the most commonly used hunting technique. However, a 2001 study which deployed maximum depth recorders found that 83% of Wedge-tails dived during foraging trips with a mean maximum depth of 14 m and that they could achieve a depth of 66 m (Burger, 2001).

Breeding behaviour

The Wedge-tailed Shearwater breeds in colonies on small tropical islands. Breeding seasons vary depending on location, with synchronised breeding seasons more common at higher latitudes. Northern hemisphere birds begin breeding around February, southern hemisphere birds begin around September. Wedge-tailed Shearwaters display natal philopatry
Broadly, philopatry is the behaviour of remaining in, or returning to, an individual's birthplace. More specifically, in ecology philopatry is the behaviour of elder offspring sharing the parental burden in the upbringing of their siblings, a classic example of kin selection...

, returning to their natal colony to begin breeding at the age of four.

Wedge-tailed Shearwaters are monogamous, forming a long term pair bond that lasts for several years. Divorce between pairs occurs after breeding seasons that end in failure. Nesting either in burrows or sometimes on the surface under cover. Pairs call frequently as a pair, both to reinforce the pair bond and warn intruders away from their territory. Parents also call to their chicks. The call is long, with an inhaling component (OOO) and exhaling component (err); their Hawaiian name ua’u kani means moaning petrel. Both sexes participate in digging a burrow, or repairing the burrow from last year. Nesting burrows of other species are also used. The breeding season of the Bonin Petrel
Bonin Petrel
The Bonin Petrel, Pterodroma hypoleuca, is a seabird in the family Procellariidae. It is a small gadfly petrel that lives in the waters of the north west Pacific and nests on islands south of Japan and in the Northwestern Hawaiian Islands...

 in Hawaii is timed to avoid that of the Wedge-tail; in years where Bonin Petrel chicks are still in burrows when Wedge-tails return to begin breeding these chicks are killed or evicted. It attends these colonies nocturnally
Nocturnal animal
Nocturnality is an animal behavior characterized by activity during the night and sleeping during the day. The common adjective is "nocturnal"....

, although non-breeding Wedge-tails are often seen at the surface throughout the day and breeding birds will rest outside their burrows before laying.

Both sexes undertake a prelaying exodus in order to build up energy reserves, this usually lasts around 28 days. A single egg is laid, if that egg is lost then the pair will not attempt another that season. After laying the male usually undertakes the first incubation stint. Both sexes incubate the egg, in stints that can last up to 13 days. Incubation takes around 50 days. After hatching the chick is brooded for up to six days, until it is able to thermoregulate, after which it is left alone in the nest while both parents hunt for food. It is initially fed with stomach oil
Stomach oil
Stomach oil is the light oil composed of neutral dietary lipids found in the proventriculus of birds in the order Procellariiformes. All albatrosses, procellarids and storm-petrels use the oil...

, an energy rich waxy oil of digested prey created in the parent’s gut; later it is fed both solids and stomach oil. Like many procellariids Wedge-tailed Shearwater parents alternate long and short trips to provide food, with the parents alternating between short foraging trips (1-4 days) and long trips (about 8 days), the two parents coordinating their feeding effort. Chicks increase in size to 560 g (larger than the adults) then drop to around 430 g before fledging
Fledge is the stage in a young bird's life when the feathers and wing muscles are sufficiently developed for flight. It also describes the act of a chick's parents raising it to a fully grown state...

. Fledging occurs after 103-115 days, after which the chick is independent of the adult.

Known breeding colonies include:
  • Heron Island, Australia
  • Lady Elliot Island
    Lady Elliot Island
    Lady Elliot Island is the southern-most coral cay of the Great Barrier Reef, Australia. The island lies north-east of Bundaberg and covers an area of approximately . The island is home to a small eco resort and an airstrip, which is serviced daily by flights from Bundaberg, Hervey Bay,...

    , Australia
  • Lord Howe Island
    Lord Howe Island
    Lord Howe Island is an irregularly crescent-shaped volcanic remnant in the Tasman Sea between Australia and New Zealand, directly east of mainland Port Macquarie, and about from Norfolk Island. The island is about 11 km long and between 2.8 km and 0.6 km wide with an area of...

    , Australia
  • Montague Island
    Montague Island
    Montague Island is 9 kilometres offshore from Narooma on the south coast of New South Wales, Australia.-Lighthouse:On the island is a lighthouse maintained by the Australian Maritime Safety Authority. The lighthouse was designed by James Barnet and built in 1881. It was automated in 1986 and...

    , Southern New South Wales
    New South Wales
    New South Wales is a state of :Australia, located in the east of the country. It is bordered by Queensland, Victoria and South Australia to the north, south and west respectively. To the east, the state is bordered by the Tasman Sea, which forms part of the Pacific Ocean. New South Wales...

    , Australia
  • North West Island
    North West Island
    North West Island is a coral cay in the southern Great Barrier Reef, located 75 kilometres northeast of Gladstone, Queensland. North West Island forms part of Capricornia Cays National Park and with an area of 1.05 km², the island is the second largest coral cay in the Great Barrier Reef...

    , Australia
  • Muttonbird Island, Coffs Harbour, Northern New South Wales, Australia
  • Manana
    Mānana Island is an uninhabited islet located off Kaupō Beach, near Makapuu at the eastern end of the Island of Oahu in the Hawaiian Islands. In the Hawaiian language, mānana means "buoyant"...

     Island, Hawaii
    Hawaii is the newest of the 50 U.S. states , and is the only U.S. state made up entirely of islands. It is the northernmost island group in Polynesia, occupying most of an archipelago in the central Pacific Ocean, southwest of the continental United States, southeast of Japan, and northeast of...

    , USA
  • Ilot Maitre, Noumea
    Nouméa is the capital city of the French territory of New Caledonia. It is situated on a peninsula in the south of New Caledonia's main island, Grande Terre, and is home to the majority of the island's European, Polynesian , Indonesian, and Vietnamese populations, as well as many Melanesians,...

    , New Caledonia


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