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White-tailed tropicbird Phaethon lepturus catesbyii


White-tailed Tropicbird landing at Warderick Wells. Photo by Dave Lee 1999.

At a glance

  • Declining with 3300-5300 breeding pairs

  • Breeds pan-tropically (all tropical oceans)

  • Smallest of the two species of tropicbird in the region

  • Confined to cavities in cliffs, away from introduced predators

  • Greatest threats are invasive species and loss of habitat

  • Tropicbirds were recently moved to a separate order of seabirds

Index


 

Identification

Adults

Adult tropicbirds are easily identified by their long, streamer-like tails. The only other streamer-tailed seabirds in the region are Long-tailed Jaegers which are dark instead of white. This species can be distinguished from the Red-billed Tropicbird by the sleek black stripes on the top of the White-tailed Tropicbird's secondary and axillary coverts versus the fine black barring on the Red-billed Tropicbird's back and axillary coverts. In the hand, they can be distinguished by measuring the body (bill color does not always work). White-tailed Tropicbirds are 14-16 inches (36-40 cm) long, not including streamers. Red-billed Tropicbirds are 18-20 inches (46-50 cm).

Juveniles


Juvenile tropicbirds are difficult to separate at sea. The barring on the back of the juvenile White-tailed tropicbird is more coarse (this barring transforms to the clear, thin lines in the adult). A better field mark is the black line of feathers that projects through the eye to the barring on the back of the Red-billed Tropicbird, forming a "nuchal collar" which encircles the head from the eyes. In juvenile White-tailed Tropicbirds, there is a clear break between the eye-line and the black barring on the back.

Likely locations

This species occurs in proximity to breeding sites, and regularly in the Sargasso Sea and the Gulf Stream to Cape Hatteras and points east. Occasionally, individuals occur farther north along the Atlantic Coast. Storm displaced individuals can occur anywhere along the North American coast. 

Alternative Common Names

Longtail (Bermuda), Bosun Bird, Yellow-billed Tropicbird, Phaéton à bec jaune (French), Rabijunco cola blanca (Spanish)

Systematics

The White-tailed Tropicbird is the smallest, most common and most widely distributed of the three species of Phaethon. Five subspecies of Phaethon lepturus are recognized, two of which occur in the Atlantic. Wing length, size, patterns of black in the primaries, and bill color are the main characters used to separate subspecies. P. l. ascensionis breeds in the eastern Atlantic on Ascension Island and on islands in the Gulf of Guinea. P. l. catesbyii breeds in Bermuda and the West Indies. The five outermost visible primaries of P. l. catesbyii have black extending to near the tips of the feathers, whereas the other races typically have only four primaries with black and broad white tips. The bill of most adult West Indian birds is orange, not yellow. This species is known from late-Holocene vertebrate fossil deposits on several large islands in the West Indies (incl. Antigua, Crooked Island).

Tropicbirds have until 2008 been classified as primitive members of the Order Pelicaniformes and are still grouped by official naming committees 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! This change could be a big economic stimulus to the struggling field guide industry.

Distribution

Tropical Pacific, Indian, and Atlantic Oceans. They breed on oceanic islands and disperse throughout adjacent tropical seas. In the Western North Atlantic, White-tailed Tropicbirds are represented by an endemic sub-species P. l. catesbyii, that nests in the Bahamas, the Greater Antilles, Northern Lesser Antilles, and on Bermuda. There are reports of nesting attempts at Dry Tortugas in the Florida Keys. At sea these birds range through the Caribbean and Sargasso Seas, the Gulf of Mexico and occur regularly in the Gulf Stream north to North Carolina.

Between 3300 and 5300 pairs nest in the Western North Atlantic, with 800-1100 of those in Bermuda. Another recent estimate (in Bradley and Norton 2009) puts the population at 2500 pairs. They have been reported from 203 breeding sites, 14 of which are thought to be extirpated and many others have declined significantly.

White Tailed Tropicbird Nesting Sites in the West Indies

Biology

At Sea

Few detailed studies at sea. Highly pelagic, mostly solitary. Typically flies 20 m or more above the surface of the ocean. Birds rest while floating on the surface. Often give shrill scream in flight. When food is spotted, they hover with head and bill pointing down.

Tropicbirds are plunge divers and often spiral down with wings partly open to compensate for the movement of the prey.  Typically remain underwater for only several seconds.
Fish are captured transversely in bill, and swallowed under water or when the bird is resting on the surface. They do not carry food aloft in bill. Major food items are flying fish and squid.

Adults can swallow prey up to 15-18% of total body weight. They sometimes follow boats and capture flying fish flushed by the vessel’s wake.
Nesting individuals are known to forage up to 80-116 km away from nesting sites and typically remain at sea one to three days when actively feeding chicks. Long-range post nesting movements away from breeding sites are the norm (up to 1,000 km). Non-breeding adults forage in the Gulf of Mexico, Sargasso Sea and in the Gulf Stream where they are often associated with oceanic fronts. Hurricanes frequently displace tropicbirds long distances, even carrying some far inland.

At Nesting Sites

Females lay a single egg per nesting attempt. Nest sites are any rock crevice where one bird can sit out of direct sun and rain, though more protected sites seem to be preferred. Sites begin just above the zone where sea spray keeps the rocks permanently wet and end where dense vegetation occludes nesting crevices.

Birds give an extremely unpleasant alarm call and bite viciously with serrated bills when approached or handled. In the Bahamas, nesting begins in March with hatching in May and June and fledging from late July to mid-September. Both parents incubate, brood young chicks, and provide food. Chicks are fed by at least one parent on most days. Wingate (pers. comm.) hypothesizes that the aggressiveness of adults in defense of nests and small chicks has probably prevented the extinction of this subspecies because most of the remaining nest sites are on islands that rats have invaded.

Between seasons, pairs usually return to the same crevice, though local moves between sites have been observed. Peregrine Falcons and pet or feral dogs are known to prey on adults and chicks at the nests, while rats (esp. more carnivorous Norway Rats) attack eggs, chicks, and adults. 

Current Population


Location Sites Low Estimate High Estimate
Bermuda 13 811 1110
Bahamas 52 349 757
Florida Keys 1 1 1
Turks and Caicos 22 292 418
Cuba 4 82 102
Cayman Islands 2 60 120
Jamaica 7 88 162
Dominican Republic 6 1083 1115
Haiti 4 4 40
Navassa 1 5 5
Puerto Rico 18 321 765
United States Virgin Islands 19 27 146
British Virgin Islands 13 31 126
Anguilla 3 2 7
St. Maarten 2 0 0
Dominica 3 12 50
Saba 5 7 45
St. Eustatius 1 1 1
St. Martin 1 4 6
Guadeloupe 10 90 126
Martinique 2 51 60
Antigua and Barbuda 4 15 65
St. Lucia 3 1 20
Grenada 1 0 0
St. Vincent and the Grenadines 5 5 50
Trinidad and Tobago 1 0 1
Total 203 3341 5298

Conservation Status

Rare and declining. Only protected in Bermuda. Over a four-year period, one, large (~80 pairs) colony declined by over 80% as a direct result of predation by three pet dogs (Lee and Mackin 2004). The West Indies population will continue to decline as more of the less accessible sites are visited by an expanding tourist industry and as predators (even temporary ones such as pet dogs) are introduced.

Tropicbirds are highly vulnerable to oil spills and the resulting longer-lived tar balls found in marine environments. Birds returning to nesting sites in Bermuda with even modest oil fouling had reduced success in both incubation and fledgling (Wingate, pers. comm.), and adults often failed to return to nests suggesting mortality from oiled feathers. The current plans to increase offshore drilling along the coast of the Southeastern United States could add significant stress to the already reduced populations in the Western North Atlantic.

Conservation Needs

Population estimate dropped from 10,000 pairs in the early 1980s (van Halewyen and Norton 1984) to 4,500-5,300 pairs by 2000. Schreiber and Lee listed the species as near threatened, but, in light of recent updated numbers that show declines (particularly in Bermuda), the species should be placed in the vulnerable or endangered category.

The global population is estimated to be 20,000 pairs (Lee and Walsh-McGehee 2000), with some indications that the West Indian birds have decreased even more in the current decade. Some of this may be a result of reporting and more accurate surveys. However, there are a number of colonies that were depleted during this period. Prior to the arrival of man (~5,000 years ago) in the West Indies region this species certainly nested on the main islands as well as offshore cays, and populations were probably several orders of magnitude larger than those observed today.

Monitoring

A primary conservation need is the systematic monitoring of existing nesting colonies. At this time, the species' existence in the region is dependent on the continued survival of small, widely scattered, isolated, and for the most part unprotected nesting sites.

Because of the broad distribution of White-tailed Tropicbirds in the region and their distinctive appearance, this species should be promoted as the flagship for local and regional seabird conservation. These charismatic birds face all of the conservation issues of the other seabirds nesting in the region and are valued for tourism.

If you live near or frequently visit tropicbird colonies and would like to sign up to monitor a population, please contact us.

Conservation of Nesting Sites

While they face some issues at sea (oil spills and other environmental contaminates), the major conservation focus needs to be at their nesting sites. Destruction of habitat and contamination with invasive species are difficult problems to address, as many of these sites are in remote areas that are costly to patrol.

Poaching is a potential problem, though the most accessible pairs have already been extirpated (the birds were eaten frequently through the 20th century. M
ost of today's population declines are not the result of direct human mortality. Egging and hunting of tropicbirds is now limited and declining. There is no evidence that either tropicbird species in the Atlantic is frequently caught by pelagic fisheries, and the local tropical fisheries for the most part are limited to near shore habitats. Availability of nests sites is a critical factor, and artifical nesting structures placed in active nesting areas are often used within the first season by the birds. It would definitely be possible for island residents to build nest sites and attract birds to areas where no predators exist or in places that are inaccessible to predators (e.g. roof tops). Such a program already exists in Bermuda.

The current threats are indirect issues caused by human activity: introduced predators, introduced plants, and loss of nest sites.
Natural causes of mortality or nesting sites become more important as isolated populations continue to decline.  Disease, natural predators (land crabs, night herons), erosion, or severe weather such as hurricanes (often filling nest cavities with sand, or removing all the substrate in a nest cavity making the sites unusable to nesting adults).

Exotic plants are an issue. In Bermuda where tropicbirds formerly nested under long, course native grasses and cedars, habitat disturbance and invasive exotics have prevented use of traditional sites. Additionally the roots of introduced Australian pines (Casuarina equisetifolia) often destroy the limestone cliffs, particularly when major storms topple and uproot clusters of these trees.

Plans to eradicate invasives from existing colonies are under development, and conservation organizations are encouraged to fund such activities.

Education

Education of both the agencies and organizations overseeing local conservation and the general public is needed. People inherently do not understand the vulnerability of seabirds and other long-lived, slowly-reproducing species.

Successful nesting by this species is incompatible with current pattens of developmant on islands. Of particular concern is the tourist industry and their insistence on taking clients to remote pristine islands in the name of ecotourism. The land and marine resources of the wider Caribbean are fragile and cannot bounce back from environmental degradation the way temperate, continental habitats can.

This species is particularly attractive due to its distinctive appearance and its iconic status as a symbol of tropical marine landscapes. Visits to cays and other areas with nesting colonies should be limited to September-February, when the birds are at sea.

The development of oceanfront properties can negatively affect nesting sites. Developers quarry and terrace sea cliffs for residential housing construct walls around coastal areas with cement blocks to prevent damage by storms. Construction of coastal roads can cause direct loss of nesting habitat, and vibrations from traffic can cause loss of nesting cavities or entire cliff faces.

Development also brings with it pet animals that over time will eliminate populations. A good example is the small population that persists along the coast of San Salvador in several locations. If they are to persist, these birds need special protection from the rats, cats, and dogs that have been introduced there.

Pet dogs have proven in several cases to be devastating. The tropicbirds are attracted to the bold markings on black and white terriers (and likely any black and white dog) and will actually attempt to land on the dogs' backs. The dogs usually end up killing or crippling the birds, and a single terrier can decimate a small colony in a matter of hours (Wingate, pers. comm.). Visitors throw bottles and other trash into nesting cavities, and sometimes tease incubating birds with sticks.

In Bermuda, protocols have been developed for the care, feeding and release of orphaned chicks. Use of traps and rat bait at nesting areas in Puerto Rico decreased egg and chick predation and increased hatching and fledgling success by 30-50% (Schaffner 1988). A concerted education and conservation effort at all colonies in the region is needed to stop the decline of this species.

Photos

Selected References

Lee, D.S.,  Mackin, W. A. 2004. Demise of a White-tailed Tropicbird colony in the Exumas Land and Sea Park. Bahamas Journal of Science.11(2): 2-12.

Lee, D. S., Walsh-McGehee, M. 1998. White-tailed Tropicbird (Phaethon lepterus). In A. Poole and F. Gill (eds.), Birds of North America, Inc., Philadelphia, Pennsylvania, 353:1-24.

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

Schaffner, F. C. 1988. The breeding biology and energenetics of the White-tailed Tropicbird
(Phaethon lepturus) at Culebra, Puerto Rico, Ph.D. dissertation, University of Miami, Miami, Florida.

Schreiber, E. A., Lee, D. S., eds. 2000. Conservation and Status of West Indiean Seabirds. Ruston: Society of Caribbean Ornithology, Special Publication No. 1, 223 pp.

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. Ruston: Society of Caribbean Ornithology, Special Publication No. 1. 223 pp.

Walsh-McGehee, M., Lee, D. S., Claridge, D. 1999. Distribution and population status of White-tailed Tropicbirds nesting in the Bahamas. Bahamas Journal of Science 6(2): 44-48.

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.

Acknowledgments

The following individuals provided unpublished information on colony sites in the West Indies region: Keval Lindsey (Antigua, Barbuda and Redondo), David Wingate (Bermuda), P. A. Buckley (Barbados), Patricia Bradley (Cayman Islands), Nicasio Vina (Cuba), Randolph Winston (Dominica), Gilles Leblond (Guadeloupe), Jose Ottenwalder (Hispaniola), Ann Hayes-Sutton (Jamaica), James Daley (Montserrat), Martha Walsh-McGehee (Saba), John Wilson (St. Kitt), Fred Schaffner and Jorge Saliva (Puerto Rico and Mona), and Judy Pierce and Betty Ann Schreiber (US Virgin Islands). Thanks also to Haven Wiley, Chuck Knapp, Mary Kay Clark, Rick and Kathy Oliver, and the Exuma Park Staff, especially Tom and Judy Barbernitz, Larry Dougan, and Evelyn Darville.
Compiled by: Dave Lee and Will Mackin

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. 2009. White-tailed Tropicbird. West Indian Breeding Seabird Atlas <http://www.wicbirds.net/wttr.html>. Last Updated: _____. Date accessed: ______.
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February 25, 2009
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