There are three recognized subspecies, but only P. a. mesonauta breeds in the neotropics. In the Atlantic this race is largely confined to the Lesser Antilles although they nest in the U.S. and British Virgin Islands, and small numbers nest in Puerto Rico and on small islands off Venezuela and Panama. In the eastern Pacific the same subspecies breeds on islands in the Gulf of California, islands off Central America, and on a number of the Galapagos Islands. Formerly nested along the coast of Ecuador and Peru. During the warmer months these birds are not confined to the proximity of their nesting islands and P. a. mesonauta can range northward in the Atlantic basin to Bermuda, in the Gulf Stream to North Carolina, and occasionally into the upper Gulf of Mexico (Lee et al. 1981). The documented period of occurrence for North Carolina's offshore waters is from 16 May-1 September (Lee 1995). The lack of reports of birds away from breeding sites in the Atlantic prior to 1981 is probably due to the fact that the species was not included in North American field guides then and people making observations assumed all tropicbird sightings were of White-taileds. Most of the identifying field marks that separate the two Atlantic tropicbirds are on their dorsal surface, and most field observations, particularly those at sea, are of the ventral surface. This fact probably calls into question some of the earlier identifications where specimens or photo identifications are lacking. There are two specimen records of storm driven individuals, one from Jamaica Bay, NY in 1963 (Bull 1964) and one from Providence, RI in 1973 (Finch 1973). In the eastern Pacific they occur regularly north to southern California and occasionally to as far north as Washington.
Distribution outside the Americas
P. a. mesonauta also nests in the Cape Verde Islands, islands off Senegal and the Madeleine Archipelago if Senegamba. There is a single nesting record from the Azores.
P. a. aethereus, the race breeding on Fernando Noronha, Ascension, and St. Helena does not nest in the neotropics, but wanders westward to waters off the coast of Brazil (Murphy 1936).
P. a. indicus is restricted to the Gulf of Suez, the Red Sea, the Persian Gulf, the Gulf of Aden, the Gulf of Oman and the eastern Arabian Sea.
Nesting: Today nesting birds are for the most part restricted to small uninhabited cays and inaccessible cliff faces of larger islands. Typically nests are in open rocky areas with sparse vegetation adjacent to the sea. Most nests are found in scrapes under large rocks and in crevices of cliff faces and, less commonly, on ledges in caves. Birds on Saba sometimes nest in large holes in volcanic rock above the tide pool level, but this is a rare occurrence (MWM pers. obser.). Nest altitude is variable, from two meters to approximately five hundred meters (Cramp 1977). Adults arrive at the breeding site four to six weeks before nesting and inspect nesting cavities. Considerations in nest site selection include thermal requirements (protection from afternoon sun), protection from rain and weather (including cyclone cycles), presence of soft substrate to cushion egg, and the direction of prevailing winds. Tropicbirds are very awkward on land due to short tarsi and anterior position of legs. They are incapable of normal bipedal locomotion so nest sites must be accessible by direct flight. Nest sites are not modified by the birds.
At sea: Highly pelagic. Range considerable distances from nesting sites to forage and typically disperse widely to other areas when nesting activities are completed. Feeding generally takes place along oceanic fronts, over areas of upwellings and other marine features that support dependable sources of prey.
While the overall known range has seen little change, there are a number of sites from which this species has been extirpated. These include Little Flat Cay in the U. S. Virgin Islands (Walsh-McGehee 2000) and Barbados, Dominica, and, possibly, St, Vincent in the Lesser Antilles (Lee and Walsh-McGehee 2000). The species formerly nested along the coasts of Ecuador and Peru, but these populations are also apparently extirpated. Because of the remote nature of modern day nesting sites there is little information on the size of historic populations at existing sites. However, based on the fact that many nesting sites now support fewer than 50 pairs, it is likely that this species was heavily impacted by both preColumbian and post European contact. This impact was further exacerbated by the introduction of rats and other exotic predators. A single breeding pair of these tropicbirds was recorded in the Azores by Furness and Monteiro (1995). This is the first European breeding record and the only documented example of a modern day range expansion for this species.
While fossils of White-tailed Tropicbirds are well known, there is no known fossil record for this species.