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Gregory R. Mann, Ph.D. {ret.}

Red-tailed Tropicbird

“Phaethon rubricauda”

The Red-tailed Tropicbird is similar to the more common White-tailed Tropicbird but is bigger, with a pure white body, red bill and a very thin red tail which is not always visible in flight. Mature birds have mostly white plumage with a conspicuous black stripe from gape, curving towards and passing through eye. Their bill is strong, curved and bright red. Their legs and feet are blue-gray with webs distally black. Red-tailed Tropicbirds also have a red tail with long, red, central rectrices or tail plumes (36-55 centimeters). The species is also known by its Maori name “Amokura”. Their calls are a guttural squawk in varying intensities and/or high whistle-like screeches. They perform complex aerial courtship displays. Acrobatics consist of flying backwards, vertical displays and circles. Red-tailed Tropicbirds nest on the Hawaiian Islands and disperses widely in tropical and subtropical areas of the Indian & Pacific Oceans; it occurs accidentally off southern California and along the California coast. It is more pelagic and is usually seen far out at sea.

Red-tailed Tropicbirds begin breeding after 4 years of age. Adults generally return to the same nest site each year. Nest sites are usually located in sheltered areas from the sun (base of a tree, in shrubs, next to a structure). The female lays 1 large egg, ranging in color from reddish brown to purplish black, directly on the ground in the shade of vegetation, a log or rocks. Re-laying can occur if the first egg is lost or infertile. Incubation period varies from 39-51 days. Both parents incubate the egg. Average incubation shift lengths range from 8-9 days in some colonies. During the breeding season, the feathers of some birds take on a pinkish flush.  Adult Red-tailed Tropicbirds hunt alone and rarely fish within sight of land. They hunt by plunge-diving, wings half-folded, into the water to mostly catch flying fish, mackerel, dolphinfish and squid. Red-tailed Tropicbirds have weak feet & legs and thus, are poor swimmers and cannot walk well on land either. This makes them extremely vulnerable to terrestrial predators, such as rats, cats and pigs. The Red-tailed Tropicbird is very rare as a breeding species on the granitic islands, perhaps because it is unable to coexist with rats & cats or because of human persecution in the past. Red-tailed Tropicbirds spend most of their life far out to sea, except when they come in to land to breed. They have an average life-span of 16-years.

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