'Ua'u, the Hawaiian Petrel

'Ua'u travel as far as Alaska and Japan during nesting season to feed their young
A grey head, back and wings contrast with a snowy underside on this seabird. Its legs are pink and black.

Jim Denny


`Ua'u (Hawaiian Petrel)

(Pterodroma sandwichensis)

Status: Endangered. Endemic.

Description: About 16 inches (head to tail). Head, wings, and tail are black. Back is slightly darker. Forehead and underparts are white. Feet are webbed, black at the toes, and pinkish toward the heel. Calls can be heard at night in their nesting colony. Sounds like oo-A-oo, and makes yapping sounds like a small dog. This is the only endangered seabird in Hawai'i.

Current Distribution: Largest known nesting colony located at the top of Mount Haleakalā, Maui at higher elevations (7,000 to 10,000 feet). Small numbers of nests have been found on the West Maui Mountains; Mauna Loa, Hawai'i; Lānai; and Kauai. 'Ua'u have been heard going into valleys on Moloka'i.

Population Size: Estimated 3,000-4,000 breeding pairs, approximately 8,000-10,000 birds within Haleakalā National Park.

Former Status and Distribution: Once numerous throughout the Hawaiian Islands. In the early and mid-1900s observers noted high numbers of 'ua'u occurring on all major Hawaiian Islands, except O'ahu. 'Ua'u were found nesting at all elevations, including sea level.

History: Early Hawaiians considered the young 'ua'u as a delicacy. Chicks were tabooed and reserved for consumption only by ali'i (Hawaiian royalty). The ali'i sent their workers to gather the young birds. The workers inserted sticks into the long nesting burrows, twisted the stick into the downy feathers of the chicks and then pulled the chicks out of the nest. 'Ua'u were also caught as they flew to their nests at night by nets that were placed along mountain ridges.

Feeding Habits: 'Ua'u feed mainly on squid. They search for food over deep waters of the ocean during the day and return to nesting colony at night. 'Ua'u are at their Maui nesting colony from February through November. Birds are at sea during December and January.

Nesting Habits: Nests are in burrows located on steep slopes. Burrows are 3 to 30 feet long. Pairs mate for life. The female lays only one egg per year. If this egg fails, the female will not re-nest. Male and female share in egg incubation. Incubation is about 56 days.

Parenting: Male and female share in feeding of young. Young are fed until they are double the size of the parents. Parents will then abandon the young, around September of each year, and leave the nesting colony until the next season.

Young Birds: Young birds are left alone in their burrows to fast (see Parenting). Once the young birds lose enough weight, they leave their nest for the open ocean. These young fledglings leave their nests at night, in October. Scientists believe that 'ua'u use the stars to navigate. Young birds will remain at sea for 3 to 6 years.

Seabird Groundings: 'Ua'u often confuse lights from land with stars. 'Ua'u circle around the lights, become tired and fall to the ground. 'Ua'u groundings occur throughout the island of Maui, on Kaua'i and Hawai'i. Press releases and brochures are disseminated during the “grounding season” (October and November) to ask the Maui community for help in retrieving grounded birds.

Reasons for Population Decline: Loss of habitat due to land development; degradation of land by feral goats and pigs; predation by introduced mongooses, feral cats, rats and dogs.

Current Threats: Predation by mongooses, feral cats, rats and dogs. Habitat loss and seabird groundings are also threats to the population. 'Ua'u are known to collide into human-made objects that are not part of their natural habitat. 'Ua'u are sometimes injured when they hit the objects and may die. Examples of these objects include towers, electric and telephone lines, buildings, antenna towers, etc. Construction activities have also caused fledging failures where chicks die at the nest.

Current Management: Predator control occurs at the nesting colony at Haleakalā. Fences around the nesting colony keep goats, pigs and dogs from entering the colony. Biologists check nests regularly. Public awareness and education through press releases and brochures aid in retrieval of grounded seabirds.

Similar Species: 'Ao (Newell’s shearwaters) are listed as Threatened under the Federal Endangered Species Act and are found on Kaua'i. Kaua'i biologists have retrieved up to 2,000 Newell's shearwaters during seabird groundings. Some Newell's shearwaters are retrieved on Maui during the 'ua'u grounding season.

'Ua'u kani (Wedge-tailed shearwaters) are numerous throughout the Hawaiian Islands. Large numbers of 'ua'u kani are retrieved during the 'ua'u grounding season.

Prepared by:
Haleakalā National Park
Endangered Wildlife Management, 2018

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'Ua'u chick covered in downy feathers stretches its legs at burrow entrance

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For additional information reguarding 'ua'u and other seabirds that call maui home, check out our partners Maui Nui Seabird Recovery Project.

Last updated: October 15, 2019

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Mailing Address:

Haleakalā National Park
PO Box 369

Makawao, HI 96768


808 572-4400

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