Storm petrels are the smallest of all the seabirds, ranging in size from 13-26 cm in length. There are two body shapes in the family; the Oceanitinae have short wings, square tails, elongated skulls, and long legs; the Hydrobatinae have longer wings, forked or wedge-shaped tails and shorter legs. The legs of all storm petrels are long but are unable to support the bird's weight for more than a few steps. The plumage of the Oceanitinae is dark with white underparts. Hydrobatinae are mostly dark in colour with varying amounts of white on the rump.
Habitat and Distribution
Storm petrels are found in all the world's oceans and in most of its seas. The Oceanitinae are typically found in the southern hemisphere and the Hydrobatinae in the northern hemisphere.Several species of storm petrel undertake migrations after the breeding season. The most widely travelled migrant is the 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.
They feed on planktonic crustaceans and small fish picked from the surface, typically while hovering.
Storm petrels nest colonially, for the most part on islands, although a few species breed on the mainland, particularly Antarctica. Nesting sites are attended nocturnally in order to avoid predators. A single egg is laid by a pair in a breeding season. Both sexes incubate in shifts of up to six days. The egg hatches after 40 or 50 days.