Wedge-tailed Shearwater

Overview

The wedge-tailed shearwater (Ardenna pacifica) is a medium-large shearwater in the seabird family Procellariidae, known by the Hawaiian name Uau Kani. It is the largest of the tropical shearwaters and is sometimes referred to as a muttonbird. The species is monotypic, meaning no subspecies are currently recognised.

Identification

• The species exhibits two colour morphs: a pale morph with grey-brown upperparts and white underparts, and a dark morph that is uniformly dark grey-brown.
• It possesses a large, wedge-shaped tail that is likely an adaptation to aid gliding.
• The bill is dark, and the legs are salmon pink and set far back on the body to facilitate swimming.
• The call is described as long, with an inhaling and exhaling component that sounds like a moan, reflected in the Hawaiian name 'ua'u kani.

Habitat

Wedge-tailed shearwaters are found throughout the tropical Pacific and Indian Oceans, generally between latitudes 35°N and 35°S. They breed in colonies on small tropical islands, including areas off Japan, the Hawaiian Islands, the Seychelles, and Australia. The species typically attends breeding colonies nocturnally, although non-breeding individuals are often seen at the surface during the day.

Diet

This species feeds pelagically on fish, squid, and crustaceans, with fish making up 66% of its diet, most commonly goatfish. While surface feeding was previously thought to be primary, contact-dipping is now recognised as the most common hunting technique. Notably, 83% of foraging trips involve diving to a mean maximum depth of 14 m, with capabilities reaching up to 66 m.

Did you know?

Native Hawaiians named the bird 'Uau Kani' specifically to reflect the nature of its melodic call, which resembles a moan. This species is monogamous, forming pair bonds that last for several years, though divorce may occur after breeding seasons that end in failure.