Shearwaters are medium-sized long-winged seabirds. There are more than 25 species of shearwaters, four large species in the genus Procellaria, three large species in the genus Calonectris, and 19 mostly smaller species in the genus Puffinus. Those in Procellaria are usually called 'petrel', though they are thought to be more closely to the shearwaters than to the other petrels.

These birds are most common in temperate and cold waters. They are pelagic outside the breeding season.

These tubenose birds fly with stiff wings, and use a “shearing” flight technique to move across wave fronts with the minimum of active flight. Some small species, like Manx Shearwater are cruciform in flight, with their long wing held directly out from their bodies.

Many are long-distance migrants, perhaps most spectacularly Sooty Shearwaters, which cover distances in excess of 14,000 km from their breeding colony on the Falkland Islands (52°S 60°W) north to 65°-70°N in the North Atlantic Ocean off north Norway. Short-tailed Shearwaters perform an even longer 'figure of 8' loop migration in the Pacific Ocean from Tasmania to as far north as the Arctic Ocean off northwest Alaska.

They are also extraordinarily long-lived. A Manx Shearwater breeding on Copeland Island, Northern Ireland, is currently (2003/2004) the oldest known wild bird in the world: ringed as an adult (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 to South America in winter, using waters off southern Brazil and Argentina, so this bird has covered a minimum of 1,000,000 km on migration alone.

Shearwaters come to islands and coastal cliffs only to breed. They are nocturnal at the colonial breeding sites, preferring moonless nights. This is to minimise predation. They nest in burrows and often give eerie contact calls on their nighttime visits. They lay a single white egg.

They feed on fish, squid and similar oceanic food. Some will follow fishing boats to take scraps, notably Sooty Shearwater; these species also commoly follow whales to feed on fish disturbed by them.

Shearwaters are part of the family Procellariidae, which also includes fulmars, prions and petrels.

The Sibley-Ahlquist taxonomy gives a radically different scientific arrangement for this group based on DNA studies.

List of species:

• Genus Procellaria
  • Grey Petrel, P. cinerea
  • White-chinned Petrel, P. aequinoctialis
  • Black Petrel, P. parkinsoni
  • Westland Petrel, P. westlandica

• Genus Calonectris
  • Streaked Shearwater, C. leucomelas
  • Cory's Shearwater, C. diomedea
  • Cape Verde Shearwater, C. edwardsii

• Genus Puffinus
  • Wedge-tailed Shearwater, P. pacificus
  • Buller’s Shearwater, P. bulleri
  • Flesh-footed Shearwater, P. carneipes
  • Pink-footed shearwater, P. creatopus
  • Great Shearwater, P. gravis
  • Sooty Shearwater, P. griseus
  • Short-tailed Shearwater or Mutton bird, P. tenuirostris
  • Heinroth’s Shearwater, P. heinrothi
  • Christmas Shearwater, P. nativatis
  • Fluttering Shearwater, P. gavia
  • Hutton's Shearwater, P. huttoni
  • Manx Shearwater, P. puffinus
  • Yelkouan Shearwater, P. yelkouan
  • Mediterranean Shearwater, P. mauretanicus
  • Black-vented Shearwater, P. opisthomelas
  • Townsend’s Shearwater, P. auriculatus
  • Hawaiian Shearwater, P. newelli
  • Audubon’s Shearwater, P. lherminieri
  • Little Shearwater, P. assimilis

See Shearwater for information about the town in Tasmania, Australia.