State recognized as Indigenous
NatureServe Heritage Ranking G4/G5 – Apparently secure/Secure
North American Waterbird Conservation Plan – Moderate Concern
Regional Seabird Conservation Plan - USFWS 2005
The koa‘e ‘ula or red-tailed tropicbird is a showy, white seabird (Family: Phaethontidae) related to boobies and frigatebirds. Four koa‘e ‘ula (red-tailed tropicbird) subspecies are recognized, and one (P. r. roseotincta) breeds in Hawai‘i. Adult males and females are mostly white, although sometimes with pale pinkish wash, except for partial black eye ring and short eye line, black flanks, and black shafts of outer primaries; both sexes have long, narrow, tail feathers with red shafts. Large reddish orange bill with black tip; legs and feet are very small. Flight is characterized by strong flapping interspersed with gliding; koa‘e ‘ula (red-tailed tropicbird) are capable of flying long distances. Koa‘e ‘ula (red-tailed tropicbird) usually forage alone, but occasionally with other species, most often far from land; often will follow ships. Koa‘e ‘ula (red-tailed tropicbird) captures prey by plunge diving. In Hawai‘i, diet is mainly comprised of flyingfish, but also takes squid, mackerel scads, dolphinfish, truncated sunfish, and ballonfish. Koa‘e ‘ula (red-tailed tropicbird) breed in colonies and pairs remain together for years. At the beginning of the breeding season, pairs engage in complex aerial displays. Nests are placed on the ground, and generally are a simple scrape lined with some vegetation. In Hawai‘i, breeding can occur throughout the year, but most nests are active between February and June. A single egg is laid per season, and both parents incubate the egg, and brood and feed the chick. No post-fledgling care is provided. Age at first breeding is between two and four years, and the oldest known individual was 23 years old.
Distribution & Abundance
DISTRIBUTION: Koa‘e ‘ula (red-tailed tropicbird) breed throughout the NWHI and at a limited number of sites on the main Hawaiian Islands, mostly on offshore islets, but possibly on Ni‘ihau, Ka‘ula, Lāna‘i, and Kaho‘olawe. Outside of Hawai‘i, koa‘e ‘ula (red-tailed tropicbird) breed on oceanic islands in the Indian and Pacific oceans. Outside the breeding season, adults are solitary and pelagic, and their range is poorly known.
ABUNDANCE: In Hawai‘i, the population is estimated at between 9,000 and 12,000 breeding pairs, with the largest populations occurring on Midway Atoll and Laysan. The worldwide population is estimated at 17,000 to 21,000 breeding pairs, with the majority residing in the Pacific Ocean.