SOOTY SHEARWATER

The 'Sooty Shearwater' (''Puffinus griseus'') 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 the Wedge-tailed Shearwater and the Australian Short-tailed Shearwater.

Contents

Taxonomy

Description

Distribution and movements

Behaviour

Diet

Breeding

Vocalisations

Use by humans

References

External links

Taxonomy

It appears to be related to the Great and Short-tailed Shearwater, all blunt-tailed, black-billed species, but its precise realationships are obscure (Austin 1996, Heidrich ''et al.'' 1998, Austin ''et al''. 2004). These are among the larger species of shearwater which might belong into a separate genus, ''Ardenna'' (Penhallurick & Wink 2004).

Description

This bird is 40-50 cm in length with a 95-110 cm wingspan. It has the typically "shearing" flight of the genus, dipping from side to side on stiff wings with few wingbeats, the wingtips almost touching the water. Its flight is powerful and direct, with wings held stiff and straight, giving the impression of a very small albatross. This shearwater is identifiable by its dark plumage which is responsible for its name. In poor viewing conditions it looks all black, but in good light it shows as dark chocolate-brown a silvery strip along the centre of the underwing. In th Pacific part of its range, other all-dark large shearwaters are found, but in the Atlantic, it is the only such bird.

Distribution and movements

Sooty Shearwaters breed on small islands in the south Pacific and south Atlantic Oceans, mainly around New Zealand, the Falkland Islands and Tierra del Fuego.
They are spectacular long-distance migrants, following a circular route, travelling north up the western side of the Pacific and Atlantic Oceans at the end of the nesting season in March-May, reaching subarctic waters in June-July where they cross from west to east, then returning south down the eastern side of the oceans in September-October, reaching to the breeding colonies in November.
In the Atlantic Ocean, they cover distances in excess of 14,000 km (9,000 miles) from their breeding colony on the Falkland Islands (52°S 60°W) north to 60° to 70°N in the North Atlantic Ocean off north Norway; distances covered in the Pacific are similar or larger; although the Pacific Ocean colonies are not quite so far south, at 35° to 50°S off New Zealand, and moving north to the Aleutian Islands, the longitudinal width of the ocean makes longer migrations possible. Recent tagging experiments [1] have shown that birds breeding in New Zealand may travel 74,000 km in a year, reaching Japan, Alaska and California, averaging 350 km per day.
In Great Britain, they move south in late August and September; with strong N/NW winds, they may become 'trapped' in the shallow, largely enclosed North Sea, and heavy passages may be seen flying back north up the British east coast as they re-trace their steps back to the Atlantic over northern Scotland.

Behaviour

Diet

The Sooty Shearwater feeds on fish and squid. They can dive up to 68 m deep for food [2], but more commonly take surface food, in particular often following whales to catch fish disturbed by them. They will also follow fishing boats to take fish scraps thrown overboard.

Breeding

It breeds in huge colonies and lays one white egg. These shearwaters nest in burrows lined with plant material which are visited only at night to avoid predation by large gulls.

Vocalisations

Usually silent, Sooty Shearwaters coo and croak while on the breeding grounds.

Use by humans

In New Zealand, tītī are traditionally harvested each year by the native Māori. Young birds just about to fledge are collected from the burrows, plucked and often preserved in salt. As a consequence, the consumption of cooked tītī can be somewhat of a salty experience.

References

★ 'Austin', Jeremy J. (1996): Molecular Phylogenetics of ''Puffinus'' Shearwaters: Preliminary Evidence from Mitochondrial Cytochrome ''b'' Gene Sequences. ''Molecular Phylogenetics and Evolution'' '6'(1): 77–88. (HTML abstract)

★ 'Austin', Jeremy J.; Bretagnolle, Vincent & Pasquet, Eric (2004): A global molecular phylogeny of the small ''Puffinus'' shearwaters and implications for systematics of the Little-Audubon's Shearwater complex. ''Auk'' '121'(3): 847–864. DOI: 10.1642/0004-8038(2004)121[0847:AGMPOT]2.0.CO;2 HTML abstract

★ Database entry includes a brief justification of why this species is near threatened

★ 'Bull', John L.; Farrand, John Jr.; Rayfield, Susan & National Audubon Society (1977): ''The Audubon Society field guide to North American birds, Eastern Region''. Alfred A. Knopf, New York. ISBN 0-394-41405-5

★ 'Harrison', Peter (1988): ''Seabirds'' (2nd ed.). Christopher Helm, London ISBN 0-7470-1410-8

★ 'Heidrich', Petra; Amengual, José F. & Wink, Michael (1998): Phylogenetic relationships in Mediterranean and North Atlantic shearwaters (Aves: Procellariidae) based on nucleotide sequences of mtDNA. ''Biochemical Systematics and Ecology'' '26'(2): 145–170. PDF fulltext

★ 'Penhallurick', John & 'Wink', Michael (2004): Analysis of the taxonomy and nomenclature of the Procellariformes based on complete nucleotide sequences of the mitochondrial cytochrome ''b'' gene. ''Emu'' '104'(2): 125-147. (HTML abstract)

External links

★ The Titi Project: Website of a long-term Sooty Shearwater research project in New Zealand. Recovered 2006-NOV-20

★ NPR: The Common Shearwater, Nature's Migration King. ''Day to Day'', aired August 8, 2006. Recovered 2006-NOV-20