Midway Atoll National Wildlife Refuge
Pacific Region
 

Birds of Midway Atoll

Bulwer's Petrel / Bulweria bulwerii

Photo of Bulwer's Petrel

Description

Male and female similar in size, though tarsus and bill longer in males. Plumage of sexes are alike: sooty brown above with pale band across greater wing-coverts usually visible up to 250 m; from farther away, wings appear uniformly dark above. Wings are long and pointed; bill black; legs pale-colored and short; tail long, wedge-shaped, and thick at base, but usually appears bluntly pointed in flight. Juveniles resemble adults.

 

Bulwer's Petrel
Photo credit: USFWS

 

Midway Population

Bulwer’s petrels were extirpated by rats at Midway Atoll. Small numbers of Bulwer’s petrels have been seen at Midway since the removal of rats in 1997. Artificial burrows and a calling station have been installed to re-establish a nesting colony, but as of yet, there have been no successful nests confirmed.

Feeding Habits

Fish; also fish eggs, squid, and crustaceans. The sea-strider Halobates sericeus is an important prey species during breeding season.

Breeding

Bulwer’s petrel spends less than six months each year at breeding colonies; the remainder of its time is spent at sea. Colonial and nocturnal, it does not excavate its own burrow; rather it lays a single, white egg in rock ledges or crevices, in human-made or natural cavities, or in the burrows of other species. Pairs remain faithful to both nest site and mate for several years, announcing their return to the breeding colony with sharp, barking calls from the ground near the burrow entrance. Both sexes incubate and feed the young, which reach one and a half times the average mass of the adult by 50 days of age. The young leave the nest at night when their flight feathers still are not fully developed, and immature birds are not observed on land again for at least two years.
Last updated: February 3, 2011