Procellariidae

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

The procellariids are the most numerous family of tubenoses, and the most diverse. They range in size from the giant petrels with a wingspan of around 2.0 m (6 ft 7 in), that are almost as large as the albatrosses, to the diving petrels with a wingspan of around 34 cm (13 in) that are similar in size to the little auks or dovekies in the family Alcidae. Male and female birds are identical in appearance. The plumage color is generally dull, with blacks, whites, browns and grays. The birds feed on fish, squid and crustacea, with many also taking fisheries discards and carrion. Whilst agile swimmers and excellent in water, petrels have weak legs and can only shuffle on land, with the giant petrels of the genus Macronectes being the only two species that are capable of proper terrestrial locomotion. All species are accomplished long-distance foragers, and many undertake long trans-equatorial migrations. They are colonial breeders, exhibiting long-term mate fidelity and site philopatry. In all species, a single white egg is laid each breeding season. The parents take it in turns to incubate the egg and to forage for food. The feeding area can be at a great distance from the nest site. The incubation times and chick-rearing periods are exceptionally long compared to other birds.

Many procellariids have breeding populations of over several million pairs; others number fewer than 200 birds. Humans have traditionally exploited several species of fulmar and shearwater (known as muttonbirds) for food, fuel, and bait, a practice that continues in a controlled fashion today. Several species are threatened by introduced species attacking adults and chicks in breeding colonies and by long-line fisheries.

The family Procellariidae was introduced (as Procellaridæ) by the English zoologist William Elford Leach in a guide to the contents of the British Museum published in 1820. The name is derived from the type genus Procellaria which in turn is derived from the Latin word procella meaning "storm" or "gale". The type genus was named in 1758 by the Swedish naturalist Carl Linnaeus in the tenth edition of his Systema Naturae.

Procellariidae is one of families that make up the order Procellariiformes. Before the introduction of molecular phylogenetics, the traditional arrangement was to divide the Procellariiformes into a set of four families: Diomedeidae containing the albatrosses, Hydrobatidae containing all the storm petrels, Pelecanoididae containing the diving petrels and Procellariidae containing the petrels, shearwaters and fulmars. The family Hydrobatidae was further divided into two subfamilies, the northern storm petrels in Hydrobatinae and the southern or austral storm petrels in Oceanitinae. A 1998 analysis of mitochondrial cytochrome b sequences found there was deep genetic divergence between the two subfamilies. Subsequent large-scale multigene studies found that the two subfamilies were not sister taxa. The storm petrels were therefore split into two families: Hydrobatidae containing the northern storm petrels and Oceanitidae, containing the southern storm petrels. The multigene genetic studies found that the diving petrels in the family Pelecanoididae were nested within the family Procellariidae. As a result, the diving petrels was merged into Procellariidae.

The molecular evidence suggests that the albatrosses were the first to diverge from the ancestral stock, and the austral storm petrels next, with the procellariids and northern storm petrels splitting most recently.

Within the procellariid family, a genetic analysis based on the cytochrome b gene published in 2004 indicated that the genus Puffinus contained two distinct clades and was polyphyletic. The genus was therefore split and a group of species moved into the resurrected genus Ardenna. The other genera within the family were found to be monotypic but the relationships between the genera remained unclear. This changed when a multigene genetic study published in 2021 provided a genus-level phylogeny of the family.

There are 99 species of procellariid in 16 genera. The family has usually been broken up into four fairly distinct groups; the fulmarine petrels, the gadfly petrels, the prions, and the shearwaters. With the inclusion of the diving petrels there are now five main groups.