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Red-billed Tropicbird Phaethon aetherus mesonauta


Adult Red-billed Tropicbird

At a glance

The Red-billed Tropicbird is the largest and most rare of the tropicbirds.

Nearly 60% of the total Caribbean population nests at two sites: Tobago and Saba

No published studies on the biology of this species are available for the West Indies region.

The Tropicbirds are now a separate family of seabirds, but until 2008, were classified with the Pelicans


Index

Identification:

Because of their long streamer-like tails adult tropicbirds are easy to identify. The only other streamer-tailed seabirds in the region are Long-tailed Jaegers, which are dark, not white. This tropicbird’s total length is about 46-50 cm, not including streamers, compared to the total length of the smaller White-tailed (36-40 cm without streamers). 

Adults

Red bill, long streamer tail, barred dorsal surface. Adult White-tailed Tropicbirds can have orange red bills, but lack the dorsal barring.

Juveniles

Fine dense barring on dorsal surface, blackish eye stripe joined across back of head. Bill yellow with black tip.  Juvenile White-tailed Tropicbird has much courser and less dense barring on back.

Systematics

The Red-billed Tropicbird is the largest, least common, and most narrowly distributed of the three species of Phaethon. Three subspecies of Phaethon aetherus are recognized, two of which occur in the Atlantic. Tropicbirds have until 2008 been classified as primitive members of the Order Pelicaniformes and are still grouped with those birds. However, a recent paper in Science using 19 different nuclear DNA regions found that Tropicbirds are most closely related to Columbiformes (Pigeons and allies), Mesites, and Sandgrouse. If this result bears out, tropicbirds will be their own group of convergently evolved seabirds, and the field guides will all have to be amended!

Likely locations

At and near breeding sites, remains at sea throughout remainder of the year.

Alternative Names

French: Phaethon à béc rouge

Dutch: Roodsnavelkeerkringvogel

Spanish: Rabijunco etéreo

Distribution

P. a. mesonauta occurs in the eastern Pacific (including the Galapagos Islands), Caribbean, and the Cape Verde Islands. Other subspecies are found in the tropical South Atlantic and the Red and Arabian Seas and the Persian Gulf. Regionally the species nests primarily in the Lesser Antilles, but they also nest in Puerto Rico and on islands off Venezuela and Panama. Extirpated or believed extirpated from Little Flat Cay (U.S. Virgin Islands) and Montserrat. At sea this species ranges regularly throughout the western Caribbean and adjacent Atlantic northward to Cape Hatteras and Bermuda. After storms displaced individuals may occur over a wider range.

In general this larger species replaces the White-tailed Tropicbird from Puerto Rico southward. The ranges of the two species overlap only from Puerto Rico to St. Vincent.

Distribution with important breeding sites labeled

Biology

At sea

Red-billed Tropicbirds apparently forage over more productive waters than do White-tailed Tropicbirds. This is a plunge diving species. Feeds on surface dwelling fishes.

At the nest

Today these birds breed on cliffs of inhabited islands and on remote cays as a response to human predation and introduced exotics. Nest in cavities and rock shelters. Pairs use same nest site each season. Nesting begins as early as January and continues through spring. Lay a single, heavily spotted egg. Chicks leave nest by mid summer. No studies conducted on this species in West Indies partly because of difficult accessibility of nest sites.

Current Population 

West Indies populations are estimated at 1,800 to 3,400 breeding pairs, but reliable surveys of many of the Lesser Antillean breeding sites are sketchy.

Location Low Estimate High Estimate
Puerto Rico 34 68
US Virgin Islands 209 426
British Virgin Islands 22 134
Anguilla 32 57
St. Martin 40 60
St. Maarten 3 12
St. Bartholomew 151 300
Saba 750 1000
St. Eustatius 7 70
St. Christopher and Nevis 2 10
Antigua and Barbuda153204
Montserrat440
Guadeloupe 280 475
Dominica 12 30
Martinique 61 80
St. Lucia 31 59
St. Vincent and the Grenadines 16 105
Grenada 7 35
Tobago 52 123
Venezuela 8 80
Total 1874 3368

Conservation Status

Rare and declining, but not specifically protected. Considered vulnerable in the West Indies (Schreiber and Lee 2000). Globally this species should possibly be considered as Endangered. It is likely that there are currently fewer than 10,000 pairs when all three subspecies are tallied. In the Cape Verde Islands, for example, a population reported to be fewer than 1,000 birds in 1969 had been reduced by fishermen to fewer than 100 pairs by 1990. Other populations have experienced similar declines.

Conservation Needs

The larger colonies need protection from human visitation and systematic control of exotic animals. The smaller colonies also need protection and to be given a chance to expand (construction of artificial nest sites, etc). All sites need to be protected from coastal development.

In that rats have been shown to be a major problem for White-tailed Tropicbirds, it can be safely assumed they are for Red-billed Tropicbirds as well. Many of the extant colonies are on inhabited islands with shipping ports so Rattus certainly occurs on these islands.

Feral goats present a problem on Saba and probably other nesting islands, eating vegetation, stepping in nests, and causing erosion and rock slides. Also on Saba, extensive rock quarrying operations adjacent to the major nesting area are causing problems. This mining has already eliminated many acres of habitat and is threatening adjacent nesting areas. The Saba population represents the largest breeding population in the Caribbean.

Studies on the nesting biology of this tropicbird in the West Region are needed, and, in that a number of nesting sites are on inhabited islands, it would be logistically easy to assign series of research projects to interested graduate students.

Photos     

Selected References

Hackett, S. J., R. T. Kimball, S. Reddy, R. C. K. Bowie, E. L Braun, M. J. Braun, J. L. Chojnowski, W. A. Cox, K. Han, J. Harshman, C. J. Huddleston, B. D. Marks, K. J. Miglia, W. S. Moore, R. H. Sheldon, D. W. Steadman, C. C. Witt, T. Yuri. 2008. A Phylogenetic Study of Birds Reveals their Evolutionary History. Science 320(5884): 1763-1768.

Lee, D. D. and M. Walsh-McGehee. 2000. Population estimates, conservation concerns, and management of tropicbirds in the Western Atlantic. Caribbean Jour. Sci. 36(3-4): 267-279.


Walsh-McGehee, M. 2000. Status and conservation priorities for White-tailed and Red-billed Tropicbirds in the West Indies. Pages 31-38 in E. A. Schreiber and D. S. Lee (eds.) Status and Conservation of West Indian Seabirds. Society of Caribbean Ornithology, Special Publication Number 1, 225 pp.

van Halewyn, R. and R. Norton. 1984.The status and conservation of seabirds in the Caribbean. Pages 169-222 in J. P. Croxall, P. G. Evans and R. W. Schreiber (eds). Status and Conservation of the World’s Seabirds. ICBP Tech. Publ., No. 2. 778 p.

Acknowledgements:

Martha Walsh-McGehee
West Indian Breeding Seabird Atlas by Will Mackin and David Lee is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 United States License. Based on work at www.wicbirds.net. Permissions beyond the scope of this license may be available at www.wicbirds.net.

Suggested Citation: Lee, D. S., W. A. Mackin. 2008. Red-billed Tropicbird. West Indian Breeding Seabird Atlas <http://www.wicbirds.net/rbtr.html>. Last Updated: _____. Date accessed: ______.

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