Austral storm petrels, or southern storm petrels, are seabirds in the family Oceanitidae, part of the order Procellariiformes. These smallest of seabirds feed on planktonic crustaceans and small fish picked from the surface, typically while hovering. Their flight is fluttering and sometimes bat-like.
Austral storm petrels have a cosmopolitan distribution, being found in all oceans, although only Wilson's storm petrels are found in the Northern Hemisphere. They are almost all strictly pelagic, coming to land only when breeding. In the case of most petrel species, little is known of their behaviour and distribution at sea, where they can be hard to find and harder to identify. They are colonial nesters, displaying strong philopatry to their natal colonies and nesting sites. Most species nest in crevices or burrows, and all but one species attend the breeding colonies nocturnally. Pairs form long-term monogamous bonds and share incubation and chick-feeding duties. Like many species of seabirds, nesting is highly protracted with incubation taking up to 50 days and fledging another 70 days after that.
Several species of austral storm petrel are threatened by human activities. One species, the New Zealand storm petrel, was presumed extinct until rediscovered in 2003. The principal threats to storm petrels are introduced species, particularly mammals, in their breeding colonies; many storm petrels habitually nest on isolated mammal-free islands and are unable to cope with predators such as rats and feral cats.
The austral storm petrels typically breed found in the Southern Hemisphere, in contrast to the northern storm-petrel in the Northern Hemisphere.
Several species of storm petrels undertake migrations after the breeding season. The most widely travelled migrant is Wilson's storm petrel, which after breeding in Antarctica and the subantarctic islands, regularly crosses the equator to the waters of the north Pacific and Atlantic Oceans. Some species, such as the grey-backed storm petrel, are thought to be essentially sedentary and do not undertake any migrations away from their breeding islands.