ʻUaʻu Kani

ʻUaʻu kani – Wedge-tailed Shearwater

Puffinus Pacificus

Stated-recognized	Indigenous
NatureServe Heritage Rank	Apparently secure/Secure
North American Waterbird Conservation Plan	Low concern
Regional Seabird Conservation Plan	USFWS 2005

General Information Foraging & Nesting Information Distribution & Abundance Conservation Management Current Threats Photos

The ‘ua‘u kani or wedge-tailed shearwater is a large, abundant seabird (Family: Procellaridae) that produces a variety of wails and moans that surely inspired the Hawaiian name of this bird which means “calling or moaning petrel.” Individuals have long thin wings, a wedge-shaped tail, and a hooked bill. ‘Ua‘u kani (wedge-tailed shearwater) are polymorphic, having two color phases, dark or light, and sexes are similar. Light-phase adults are grayish brown above with white underparts except for dark trailing edges of wings and tail. Dark-phase adults are uniformly sooty brown. Flight is similar to that of albatross but flaps wings with greater frequency.

Often forages in large, mixed species flocks associated with schools of large predatory fishes which drive prey species to the surface. ‘Ua‘u kani (wedge- tailed shearwater) use a variety of foraging techniques, most frequently plunges head into water while on the wing, also seizes prey will sitting on the water; often follows fishing vessels. In Hawai‘i, diet primarily consists of larval goatfish, flyingfish, squirrelfish, and flying squid.

Like most seabirds ‘ua‘u kani (wedge-tailed shearwater) breed in their natal colonies, form long-term pair bonds (although breeding failure in this species may result in divorce), have high site fidelity, lay only one egg per season, and both parents participate in all aspects of raising young. ‘Ua‘u kani (wedge-tailed shearwater) excavate burrows or nest in rock cervices. In Hawai‘i, breeding is very synchronous, and most eggs are laid in June with most young fledging in November. Birds first breed at four years of age, and the oldest known individual was 29 years old.

‘Ua‘u kani (wedge-tailed shearwater) breed throughout the NHWI and on offshore islets of most of the MHI. Outside of Hawai‘i, ‘ua‘u kani (wedge-tailed shearwater) breeds on islands throughout the tropical and subtropical Indian and Pacific oceans. Outside the breeding season, ‘ua‘u kani (wedge-tailed shearwater) migrate to the eastern Pacific.

Wedge-tailed shearwater’s or ‘Ua‘ukani, can be found in all areas on Kure’s Green Island. Not having much preference to nesting habitat, Wedge-tailed shearwater’s nest in all areas of the island. Nest sites can be found under vegetation, in open fields, on rocky, coralline substrate or even in burrows. A typical nest is a scraping the bird makes in the ground with a solitary egg laid. Wedge-tailed shearwater’s will also excavate their own burrows or use old Bonin petrel burrows. Active both day and night, they are easy to spot on Kure during breeding season.

The following management goals are important to Pacific seabird conservation: maintain, protect, and enhance habitat; eradicate or control non-natives; minimize bycatch and other negative effects of fishing; improve the effectiveness of oil spill response efforts; identify contaminates and hazardous substances; and minimize the effects of powerlines, towers, wind turbines and lights (USFWS 2005). The goal of these management actions is not only to protect seabird populations and their breeding colonies, but also to re- establish former breeding colonies thereby reducing the risk of extinction.

Humans

Historically, wanton killing for feathers (i.e., millinery trade) greatly reduced populations. Populations extirpated from Johnston, Wake, and Marcus islands by Japanese feather hunters at the turn of the last century are only recently being recolonized. Untold numbers were killed as a result of military activities in the Pacific during World War II. Between 1954 and 1964, 54,000 albatross were killed on Midway to reduce the risk of collisions with aircraft. In 1909, 300,000 birds were killed on Laysan Island. Prior to banning drift net fisheries in 1993, thousands were killed annually. In the 1990s, longline fisheries killed thousands annually.

Introduced Predators

Like all seabirds, adults and nests are susceptible to mammal predation by pigs (Sus scrofa), rats (Rattus spp.), feral cats (Felis silvestris), and the small Indian mongoose (Herpestes auropunctatus).

Human Disturbance

Laysan (Telespiza cantans) and Nihoa (T. ultima) finches will depredate eggs left unattended because of human disturbance. Trampling by humans will collapse burrows.

Contaminants

Mercury, lead, and organochlorines have been detected in Hawaiian birds.

Disease

Pox-like lesions have been observed on birds breeding on Maui and Moloka‘i.

Overfishing

Because ‘ua‘u kani (wedge-tailed shearwater) rely on predatory fish to drive prey to the surface, overfishing may eventually affect Hawaiian populations.

Artificial Lighting

Street and resort lights, especially in coastal regions, disorient fledglings causing them to eventually fall to the ground exhausted or increasing their chance of collision with artificial structures (i.e. fallout). Once on the ground, fledglings are unable to fly and are killed by cars, cats, and dogs or die because of starvation or dehydration.