Wedge-tailed Shearwater

‘Ua‘u kani / Puffinus pacificus
WTSH

 

  • Found on Kaua'i from March – November
  • In Hawiian ‘Ua‘u refers to the petrels or shearwater while kani means sound or noise of any kind. Island residents call them the "moaning bird" due to loud moans and wails that sound like cats or human babies. Vocalizations occur primarily at night in breeding colonies.
  • ‘Ua‘u kani are dark brown to brownish-gray above. Below they have white underparts with dark wing margins and undertail-coverts. They have a slender, grey hooked bill and a wedge-shaped tail. Legs and feet are a fleshy beige.
  • ‘Ua‘u kani nest in colonies, occupying natural crevices or burrows dug with its bill and feet. Wedge-tailed shearwater return to the same nest site each year.
  • They breed widely in the tropical and subtropical waters of the Indian and Pacific Oceans. They are monogamous and their courtship ritual begins shortly after arrival in late March. A pair will sit head to head, often near their burrow entrance, vocalizing two-part wailing duets.
  • In June a single, large, white egg is laid. Incubation period averages 53 days with both parents alternating shifts on the egg, with each shift lasting as long as 12 days.
  • Chicks hatch during late July through late August. Parents feed regurgitated squid and stomach oil to chicks - feeding takes place every 24 hours. Fledging occurs in approximately 100-115 days. Parent desertion of the chick typically occurs shortly before fledging.
  • Because these birds are adapted to swimming underwater, their legs are placed far back on their body, causing the birds to waddle and look awkward when trying to walk around. This is true of both adults and chicks.
  • Shearwaters are pelagic birds meaning they spend the majority of their life on the open ocean and only venture back to land to breed. Pelagic birds are powerful fliers with exceptionally long, thin wings. They can remain in flight for days or weeks, sleeping in-flight, while staying hundreds to thousands of miles offshore. They also have a special salt gland that helps them extract excess salt from their body via their nostrils. This allows them to drink seawater and ingest water from prey without accumulating toxic levels of salt in their bloodstream. 
  •  They are monogamous. Strictly nocturnal over breeding colony. Their courtship ritual begins shortly after arrival in early March at which time they will establish territories and dig burrows in preparation for egg-laying in June. A pair will sit head to head, often near their burrow entrance, vocalizing two-part wailing duets. Returning to the same nest site or area each year, ‘ua‘u kani nest in shallow burrows, 1-2 meters in length. ‘Ua‘u kani are very synchronous nesters – all lay 1 egg within a 3-week period.
  • A single, large, white egg is laid in a nesting chamber at the end of burrow. Egg-laying begins around the second week of June and continues throughout the month. No relaying will occur if an egg is lost. Incubation period averages 53 days with both parents alternating shifts on the egg, with each shift lasting as long as 12 days.

Facts About Wedge-tailed Shearwater

Diet
Feed during the day singly or in multi-species flocks. Consumes larval forms of goat fish, mackerel scad, and flying squid driven to the surface by schools of predatory fish, such as skipjack tuna.

Life Span
10-11 years

Size
Length: 41-46 cm (16-18 in); wingspan: 97-104 cm (38-41 in)