Birds of Midway Atoll

Red-tailed Tropicbird / Phaethon rubricauda rothschildi

	Description Mature birds have mostly white plumage. Conspicuous black stripe from gape, curving towards 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 (36-55 cm). Length: 44-47 cm (17-18 in), 80-102 cm including tail streamers; wingspan: 104 cm (41 in); average life span: 16 years.
Red-tailed Tropicbird Photo credit: Sandra Hall/USFWS

Midway Population

In 1984, about 5,000 nesting pairs were estimated to breed on all three islands of Midway Atoll, the largest nesting population within the Hawaiian Islands. Red-tailed Tropicbirds nest in the Hawaiian Islands and disperse widely in tropical and subtropical areas of the Indian and Pacific Oceans.

Vocalization

A guttural squawk in varying intensities and high whistle like screeches.

Feeding Habits

Usually feeding during the day, Red-tailed Tropicbirds are solitary feeders and rarely fish within sight of land. The Red-tailed Tropicbird dives, wings half-folded, into the water to catch their prey. Red-tails 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 backwards, vertical displays and circles. Pair bonding behavior is minimal. Birds begin breeding after 4 years of age.

Nest year round with peak activity from March through August. 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 a single egg, ranging in color from brown to purplish black, allowing them to recognize and retrieve their own eggs. Relaying can occur if the first egg is lost or infertile. Incubation period varies from 39-51 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 Pelecaniformes, 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 six 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.