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Shearwater

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For other uses, see Shearwater (disambiguation).

Shearwaters
Great shearwater
Scientific classification
Kingdom:
Animalia
Phylum:
Chordata
Class:
Aves
Order:
Procellariiformes
Family:
Procellariidae
Genera

Calonectris
Puffinus
Ardenna

Diversity
3 genera and c. 30 species

Shearwaters are medium-sized long-winged seabirds in the petrel family. They have a global marine distribution, but are most common in temperate and cold waters, and are pelagic outside the breeding season.

Description

These tubenose birds fly with stiff wings and use a "shearing" flight technique (flying very close to the water and seemingly cutting or "shearing" the tips of waves) to move across wave fronts with the minimum of active flight. This technique gives the group its English name.[1] Some small species, like the Manx shearwater are cruciform in flight, with their long wings held directly out from their bodies.

Behaviour

Movements

Many shearwaters are long-distance migrants, perhaps most spectacularly sooty shearwaters, which cover distances in excess of 14,000 km (8,700 mi) from their breeding colony on the Falkland Islands (52°S 60°W) to as far as 70° north latitude in the North Atlantic Ocean off northern Norway. One study found Sooty shearwaters migrating nearly 64,000 km (40,000 mi) a year, which would give them the longest animal migration ever recorded electronically.[2] Short-tailed shearwaters perform an even longer "figure of eight" loop migration in the Pacific Ocean from Tasmania to as far north as the Arctic Ocean off northwest Alaska. They are long-lived. A Manx shearwater breeding on Copeland Island, Northern Ireland, was (as of 2003/2004) the oldest known wild bird in the world: ringed as an adult (when at least 5 years old) in July 1953, it was retrapped in July 2003, at least 55 years old. Manx shearwaters migrate over 10,000 km (6,200 mi) to South America in winter, using waters off southern Brazil and Argentina, so this bird had covered a minimum of 1,000,000 km (620,000 mi) on migration alone.

Breeding

Shearwaters come to islands and coastal cliffs only to breed. They are nocturnal at the colonial breeding sites, preferring moonless nights to minimise predation. They nest in burrows and often give eerie contact calls on their night-time visits. They lay a single white egg. The chicks of some species, notably short-tailed and sooty shearwaters, are subject to harvesting from their nest burrows for food, a practice known as muttonbirding, in Australia and New Zealand.

Feeding

They feed on fish, squid, and similar oceanic food. Some will follow fishing boats to take scraps, commonly the sooty shearwater; these species also commonly follow whales to feed on fish disturbed by them. Their primary feeding technique is diving, with some species diving to depths of 70 m (230 ft).

Taxonomy

There are about 30 species: a few larger ones in the genera Calonectris and Ardenna and many smaller ones in Puffinus. The Procellaria and Bulweria petrels were believed to belong to this group, but are only distantly related based on more recent studies, while the Pseudobulweria and Lugensa "petrels" are more closely related.[3][4] The genus Puffinus can be divided into a group of small species close to Calonectris and a few larger ones more distantly related to both.[5]

List of species

Shearwater flock in Unimak Pass

References

  1. ^ "Shearwaters". Oxford English Dictionary (Online ed.). Oxford University Press. (Subscription or participating institution membership required.)
  2. ^ "Longest Animal Migration Measured, Bird Flies 40,000 Miles a Year".
  3. ^ Bretagnolle, Vincent; Attié, Carole; Pasquet, Eric (1998). "Cytochrome-B evidence for validity and phylogenetic relationships of Pseudobulweria and Bulweria (Procellariidae)" (PDF). The Auk. 115 (1): 188–195. doi:10.2307/4089123. JSTOR 4089123.
  4. ^ Nunn, Gary B.; Stanley, Scott E. (1998). "Body Size Effects and Rates of Cytochrome b Evolution in Tube-Nosed Seabirds" (PDF). Molecular Biology and Evolution. 15 (10): 1360–1371. doi:10.1093/oxfordjournals.molbev.a025864. PMID 9787440. Corrigendum
  5. ^ 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. doi:10.1006/mpev.1996.0060. PMID 8812308.
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