Storm Petrel Bird is a tiny seabird, weighing a mere 25g or so and bearing a passing resemblance to a large House Martin. The plumage is black and sooty blackish-brown overall, with a short rounded tail, stubby head and tiny bill. The main plumage feature is the extensive white rump that 'folds around' at the sides, extending on to the lateral undertail coverts, but there is also a white band of varying extent running lengthways along the underwing, formed by white tips to the greater underwing coverts. Storm Petrel Bird flies directly and purposefully, with continuous rapid wingbeats, punctuated with short glides and turns, and when feeding it momentarily flutters and hangs with its wings raised in a dihedral, close to the surface of the water, alighting briefly on occasion.
Visiting land only to nest, it is at home on the open ocean, where it spends most of its time out of sight of land. It breeds only along the north-western Atlantic coasts and in the western Mediterranean, migrating in winter as far south as South Africa. Favoured places for breeding colonies are cliffs, islands and rocky places free from ground predators and disturbance, the birds nesting fairly close to water in crevices, burrows and even stone walls.
Storm Petrel Bird has a range of vocalizations, heard around the breeding colonies which are visited only at night, the birds typically arriving at dusk and leaving before sunrise. When engaged in aerial courtship chases over the colony they give a flight call "chick!" or "ker-Chick!" varying in strength and frequency depending on how excited the birds become. A curious noise is given from the burrows, a low purring growl "arrr-r-r-r-r-r-r-r-r" or "prrrrrr-uh prrrrrr-uh prrrrrr-uh..." at a rate of 30-40 notes per second, sounding like something from a science fiction movie. It also gives another equally odd call during these audio displays, perhaps in duet, such as "i'i'i'ih'ih!" or "ge-ge-gee giggit!". Silent at sea.