Wilson's Storm Petrel

The Wilson's storm petrel, or Oceanites oceanicus, is a diminutive seabird belonging to the austral storm petrel family Oceanitidae. It is distinguished by its dark brown plumage, save for the white rump and flanks, and its small stature, measuring 16–18.5 cm in length with a wingspan of 38–42 cm. The feet of this bird protrude slightly beyond its square-ended tail during flight.

Identification Tips

When observing Wilson's storm petrel, look for the diffuse pale band along the upper wing coverts, which sets it apart from similar species. Unlike the European storm petrel, it lacks a distinctive white underwing lining. The yellow webbing between the toes, adorned with black spots in younger birds, is a notable feature for identification.

Habitat

This species is strictly pelagic outside of the breeding season, making it a rarity to spot from land. It breeds on the Antarctic coastlines and nearby islands, such as the South Shetland Islands, during the southern hemisphere's summer.

Distribution

Wilson's storm petrel enjoys a circumpolar distribution, primarily in the southern hemisphere's seas, but extends northwards during the northern hemisphere's summer. It is more commonly found in the North Atlantic than the Pacific and is often seen off the eastern coast of North America during the northern summer.

Behaviour

The flight of Wilson's storm petrel is more direct and gliding compared to other small petrels. It exhibits a unique habit of pattering on the water's surface as it forages for planktonic food items. This species is highly gregarious, often following ships and fishing boats, and can be heard emitting a soft peeping noise while feeding.

Song & Calls

While feeding, Wilson's storm petrel can be identified by its soft peeping calls, which are particularly audible when the birds gather in groups.

Breeding

Breeding takes place in colonies close to the sea, where they nest in rock crevices or small burrows. They lay a single white egg and exhibit limited walking ability, shuffling short distances to their burrows. Both parents are involved in tending the nest and feeding the chick.

Similar Species

The European storm petrel is similar in appearance but can be differentiated by its whitish underwing lining and nearly all-dark upperwing.

Diet and Feeding

Wilson's storm petrel feeds predominantly on planktonic invertebrates and occasionally on small fish from the family Myctophidae. They forage close to the ocean surface and rarely dive below it to capture prey.

Conservation Status

With an estimated world population of 8 to 20 million birds, Wilson's storm petrel is classified as Least Concern on the IUCN Red List of Threatened Species. The population is considered stable, and the species is widespread throughout its large range.