Birds of Kīlauea Point

Red-tailed Tropicbird / Phaethon rubricauda rothschildi / Koa‘e ‘ula

	Description Mature birds have mostly white plumage. Conspicuous black stripe from gape, curving toward and passing through eye. Strong decurved, bright, red, heavy beak. Legs/feet blue-gray with webs distally black. White tail with long, red, central rectrices. Vocalizations consist of guttural squawks in varying intensities and high whistle-like screeches.
Red-tailed Tropicbird - Photo credit Sandra Hall/USFWS

Population

Koa‘e ‘ula nest at Kīlauea Point then disperse widely in tropical and subtropical areas of the Indian and Pacific Oceans.

Habitat

Nest sites are usually a scrape on the ground located in sheltered areas from the sun (base of a tree, in shrubs, next to a structure) or within a shallow crevice on a cliff.

Feeding Habits

Usually feeding during the day, koa‘e ‘ula are solitary feeders and rarely fish within sight of land. They dive, wings half-folded, into the water to obtain prey. Koa‘e ‘ula consume mostly fish (flying fish, mackerel, dolphinfish, balloonfish) and squid. Their diet is about 4/5 fish and 1/5 squid.

Breeding

Perform complex aerial courtship displays. Acrobatics consist of flying backward, vertical displays and circles. Pair bonding behavior is minimal. Birds begin breeding after 4 years of age.

Adults arrive at the nesting colony in February. Nesting begins in March and most eggs will be laid in May and June. Adults generally return to the same nest site each year. The female lays a single egg, ranging in color from brown to purplish black, Relaying can occur if the first egg is lost or infertile. Incubation period is approximately 43 days. Both parents incubate the egg. Lacks brood patch. Average incubation shift lengths range from 8-9 days. During the first few weeks after hatching, chicks are attended and fed by one of its parents in shifts similar to those during incubation. Nestlings are brooded almost continuously for the first week. Feeding takes place on an average of every 17 hours. Unlike other pelican relatives, adults regurgitate food by putting their bills down the gaping chick's throat.

The chick-rearing period can range from 77 to 123 days. Chicks reach adult weight in 6 weeks. In 11 weeks, wing exercising begins and in 12-13 weeks, fledging occurs. Chicks fledge with a dark gray bill and white and gray plumage.

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