page_title: Procellariidae
section_title: Colonies
hierarchical_section_title: Procellariidae / Biology / Breeding / Colonies
context_page_description: The family Procellariidae is a group of seabirds that comprises the fulmarine petrels, the gadfly petrels, the prions, and the shearwaters. This family is part of the bird order Procellariiformes, which also includes the albatrosses, the storm petrels, and the diving petrels.
  The procellariids are the most numerous family of tubenoses, and the most diverse. They range in size from the giant petrels, which are almost as large as the albatrosses, to the prions, which are as small as the larger storm petrels. They feed on fish, squid and crustacea, with many also taking fisheries discards and carrion. 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, each pair lays a single egg per breeding season. Their 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.
context_section_description: The procellariids are colonial, nesting for the most part on islands. These colonies vary in size from over a million birds to just a few pairs, and can be densely concentrated or widely spaced. At one extreme the greater shearwater nests in concentrations of 1 pair per square metre in three colonies of more than 1 million pairs, whereas the giant petrels nest in clumped but widely spaced territories that barely qualify as colonial. Colonies are usually located near the coast, but some species nest far inland and even at high altitudes (such as the Barau's petrel).
  Most seabirds are colonial, and the reasons for colonial behaviour are assumed to be similar, if incompletely understood by scientists. Procellariids for the most part have weak legs and are unable to easily take off, making them highly vulnerable to mammalian predators. Most procellariid colonies are located on islands that have historically been free of mammals; for this reason some species cannot help but be colonial as they are limited to a few locations to breed. Even species that breed on continental Antarctica, such as the Antarctic petrel, are forced by habitat preference (snow-free north-facing rock) to breed in just a few locations.
  Most procellariids' nests are in burrows or on the surface on open ground, with a smaller number nesting under the cover of vegetation (such as in a forest). All the fulmarine petrels bar the snow petrel nest in the open, the snow petrel instead nesting inside natural crevices. Of the rest of the procellariids the majority nest in burrows or crevices, with a few tropical species nesting in the open. There are several reasons for these differences. The fulmarine petrels are probably precluded from burrowing by their large size (the crevice-nesting snow petrel is the smallest fulmarine petrel) and the high latitudes they breed in, where frozen ground is difficult to burrow into. The smaller size of the other species, and their lack of agility on land, mean that even on islands free from mammal predators they are still vulnerable to skuas, gulls and other avian predators, something the aggressive oil-spitting fulmars are not. The chicks of all species are vulnerable to predation, but the chicks of fulmarine petrels can defend themselves in a similar fashion to their parents. In the higher latitudes there are thermal advantages to burrow nesting, as the temperature is more stable than on the surface, and there is no wind-chill to contend with. The absence of skuas, gulls and other predatory birds on tropical islands is why some shearwaters and two species of gadfly petrel can nest in the open. This has the advantages of reducing competition with burrow nesters from other species and allowing open-ground nesters to nest on coralline islets without soil for burrowing. Procellariids that burrow in order to avoid predation almost always attend their colonies nocturnally in order to reduce predation as well. Of the ground-nesting species the majority attend their colonies during the day, the exception being the herald petrel, which is thought to be vulnerable to the diurnal white-bellied sea eagle.
  Procellariids display high levels of philopatry, exhibiting both natal philopatry and site fidelity. Natal philopatry, the tendency of a bird to breed close to where it hatched, is strong among all the Procellariiformes. The evidence for natal philopatry comes from several sources, not the least of which is the existence of several procellariid species that are endemic to a single island. The study of mitochondrial DNA also provides evidence of restricted gene flow between different colonies, and has been used to show philopatry in fairy prions. Bird ringing also provides compelling evidence of philopatry; a study of Cory's shearwaters nesting near Corsica found that of nine out of 61 male chicks that returned to breed at their natal colony actually bred in the burrow they were raised in. This tendency towards philopatry is stronger in some species than others, and several species readily prospect potential new colony sites and colonise
caption: Christmas shearwaters (Puffinus nativitatis) are one of the surface-breeding procellariids. Here a pair engages in some mutual preening.
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