Introduction

Tropicbirds are aptly named; they rarely stray far from tropical and subtropical seas. The White-tailed Tropicbird, the smallest and most common of the 3 species of Phaethon, is pantropical. Like the other 3 species in the genus, it nests on oceanic islands, including the Hawaiian Islands. Although there are only 3 records (nonbreeding) of this species from western North America (southern California and Arizona), this tropicbird occurs regularly off the coast of the southeastern United States and less commonly throughout the northern and eastern Gulf of Mexico. These birds originate from breeding colonies in Bermuda, the Bahamas, and the Greater and Lesser Antilles. The species also occurs in the tropical eastern Atlantic and Indian Oceans. Because of its ability to use holes in inaccessible cliffs as nest sites, the White-tailed Tropicbird is less vulnerable than most other tropical seabirds to poaching, predation of eggs and chicks by human-introduced predators, and nesting-habitat destruction.

Tropicbirds are generally among the most pelagic Pelecaniformes. Except during courtship and nesting they are seldom seen in sight of land and normally do not feed within sight of their nesting islands.

They forage over tropical and subtropical seas that typically are nutrient-poor with patchy food resources. At sea they are usually solitary, but they may congregate in small groups around temporarily available, patchy food sources. They are plunge-divers that feed largely on flying fishes and squid. Our experiences, as well as firsthand reports from charter boat captains, indicate that the birds frequently investigate boats and seem to be attracted to boats with high rigging, over which they hover as if to land. They circle the vessels, then continue on their way.

Like most tropical seabirds, White-tailed Tropicbirds are long-lived, lay but a single egg, and have an extended incubation and fledging period. They normally disperse widely from their nesting islands during the nonbreeding period, but they exhibit no known pattern of migration. Despite wide distribution, many aspects of the biology of this relatively common seabird remain unstudied. Except for studies at Puerto Rican nesting colonies by Schaffner (1988, 1990a, 1990b, 1991), little work has been published on White-tailed Tropicbirds in the Americas, and little information is available on its marine biology.