Petrel

Petrels are tube-nosed seabirds in the bird order Procellariiformes.

Description
Petrels are a paraphyletic group of marine seabirds, sharing a characteristic of a nostril arrangement that results in the name "tubenoses". Petrels include three of the four extant families within the Procellariiformes order, including the Procellariidae (fulmarine petrels, the gadfly petrels, the diving petrels, the prions, and the shearwaters), Hydrobatidae (Northern storm petrel), and the Oceanitidae (Austral storm petrel). The other Procellariiformes order are the albatross family, Diomedeidae.

Known species
All the members of the order are exclusively pelagic in distribution—returning to land only to breed.

The family Procellariidae is the main radiation of medium-sized true petrels, characterised by united nostrils with medium septum, and a long outer functional primary feather. It is dominant in the Southern Oceans, but not so in the Northern Hemisphere.

It includes a number of petrel groups, the relationships between which have finally been resolved to satisfaction.
 * The fulmarine petrels: seven species of surface predators and filter feeders, breed in high latitudes but migrate along cool currents to the north. All but Fulmarus are essentially confined to the south, Fulmarus apparently colonised the Northern Hemisphere during the Early Miocene.
 * The huge giant petrels, genus Macronectes, which are convergent with the albatrosses
 * The true fulmars, genus Fulmarus
 * Antarctic petrel Thalassoica antarctica
 * Cape petrel Daption capense
 * Snow petrel Pagodroma nivea
 * The prions: A specialised group of a few very numerous species, all southern. They have a small, fulmar-like form and mostly filter-feed on zooplankton.
 * Pachyptila, the prions proper
 * The procellariine petrels, larger or mid-sized species feeding on fish and molluscs which are fairly close to the prions:
 * Procellaria
 * Bulweria
 * Shearwaters: There are numerous species in several genera with a medium number of species.
 * Calonectris
 * Puffinus, which is two rather distinct groups of larger and smaller species
 * Pseudobulweria
 * Kerguelen petrel Lugensa brevirostris
 * The gadfly petrels: These are a considerable number of agile short-billed petrels in the genus Pterodroma which include the endangered Bermuda petrel or cahow and a considerable number of forms rendered extinct by human activity.

The families Oceanitidae and Hydrobatidae are the storm petrels, small pelagic petrels with a fluttering flight which often follow ships.

The family Pelecanoididae is the four species of diving petrels, genus Pelacanoides. These are auk-like small petrels of the southern oceans.

The word petrel (first recorded in that spelling 1703) comes from earlier (ca. 1670) pitteral; the English explorer William Dampier wrote the bird was so called from its way of flying with its feet just skimming the surface of the water, recalling Saint Peter's walk on the sea of Galilee (Matthew xiv.28); if so, it likely was formed in English as a diminutive of Peter (< Old Peterelle (?) > Late < Late  < Πέτρος < πέτρα = "stone").