White-tailed tropicbird (Phaethon lepturus)

Also known as: golden bosunbird, long-tailed tropicbird, white-tailed tropic bird, whitetailed tropicbird, white-tailed tropic-bird, yellow-billed tropic bird, yellow-billed tropicbird, yellow-billed tropic-bird
  
French: Phaéton à queue blanche
KingdomAnimalia
PhylumChordata
ClassAves
OrderPelecaniformes
FamilyPhaethontidae
GenusPhaethon (1)
SizeHead-body length: 70 – 82 cm (2)
Wingspan: 90 – 95 cm (2)
Weight220 – 410 g (2)

This species is classified as Least Concern (LC) on the IUCN Red List (1).

The white-tailed tropicbird is the smallest of the tropicbirds, a group of elegant seabirds renowned for their greatly elongated tail streamers that extend from the wedge-shaped tail (2) (3). This slender and graceful bird has a robust, yet streamlined body with long, sharply-pointed wings that provide aerodynamic efficiency while soaring on thermals far out at sea, and a stout, downward-curving bill with slit-like nostrils and serrated edges, used for holding onto slippery fish. While perfectly adapted for acrobatic aerial manoeuvres, the white-tailed tropic bird is less impressive on land. The backward-set legs and feet are short and weak and cannot support the body’s weight, limiting movement on ground to an awkward shuffle (4). Excluding a black bar on the upper wings, a black eye stripe, and black patches on the tips of the wing feathers, the white-tailed tropicbird has a predominately white plumage that often has a slight pinkish tinge (3) (5). The juveniles, however, have long, dense, greyish down that turns to white, with black barring on the back, before they take on the adult plumage (4).

A widespread seabird, the white-tailed tropicbird is found across much of the tropical waters in the southern Indian Ocean and western and Central Pacific, as well as tropical and sub-tropical parts of the Atlantic Ocean and the Caribbean (6). During the breeding season, this bird comes to land on tropical islands, but at other times, it is usually scattered far out at sea over deep, open waters (4).  

The white-tailed tropicbird breeds on small, remote, tropical islands, where it nests on cliffs and occasionally trees (5). It forages widely over deep waters, often far from the nesting site, in regions where the sea surface temperature is over 22 degrees Celsius (3).

Tropicbirds are remarkable for being able to remain at sea for indefinite periods, and can sustain long periods of flight (3) (4). In the air these birds have a tern or pigeon-like flight pattern, with rapid wing-beats, although the tropicbirds also exploit their long wingspan and streamlined body shape to attain impressive altitudes by soaring upwards on rising thermals. While resting at sea, tropicbirds float on the sea surface, due to their fully waterproof plumage, and will take to the air again after powerful beats of the wings and thrusts of the fully-webbed feet (3).

The white-tailed tropicbird feeds largely on flying fish, but may supplement this diet with squid and crustaceans (2). Once its prey is targeted, it hovers briefly with the head and bill pointed downwards, before making a rapid, vertical, spiralling plunge from 15 to 20 metres (2) (3) (4). In the water, this bird can make rapid movements, with quick turns and twists, all the while using the half-bent wings to control its body, and its prey is captured in its serrated beak. Flying fish may also be caught in flight, and the white-tailed tropicbird may seek out fish that have been flushed by boats or, more rarely, shoals of hunting tuna. On land, however, this bird is less impressive and movement is extremely awkward. The bird lies on its belly and stabs its bill into the ground, pulling itself forward in an ungainly shuffle (3).

At sea, the white-tailed tropicbird is largely solitary, but during the breeding season, this bird may collect into loose colonies or small groups (2) (3) (4). Prior to breeding, monogamous pairs engage in unusual courtship displays, with up to 20 birds flying as high as 100 metres with ritualised wingbeats, dives and calls. The birds fly in unison, make wide circles and drop the tail and streamers in an arc, before pairs leave the group and perform a descending glide or zigzag in tandem (3) (4). Although not strictly territorial, there is fierce competition for the best nesting sites, and bloody fights between birds may ensue, with stabbing, slashing and the interlocking of bills (4). A nest is created by the male in a rocky crevice that offers some shelter from the sun, or less favourably on the ground (2) (3) (4). A single egg is laid and incubated by both the male and female at intervals of 13 days for some 40 to 43 days (2) (3) (4). Once hatched, the chick is largely left alone in the nest while the parents forage out at sea. It is at this time that the chick is most vulnerable to attacks, particularly from adults of the same or different species, which are looking for nesting sites (4). The single chick fledges after 70 to 85 days in the nest, and may join the adults in undertaking nomadic movements that see the birds wander as far as 1,000 kilometres out to sea in search of favourable feeding grounds (2). The white-tailed tropicbird first breeds between two and five, with most birds breeding in their third or fourth year (4).

The white-tailed tropicbird is the most numerous of the tropicbirds (2) (6). Although not currently considered at risk of extinction, this species is threatened in parts of its range, particularly in the Atlantic where the species is few in number and declining, mainly due to loss of nesting habitat and predation by introduced mammals (2) (3) (7). The loss of around a third of its forest nesting habitat on Christmas Island also caused significant declines, while tourist and infrastructure development threatens the species across much of its range. Predation by rats has been particularly problematic on Puerto Rico, where the total population may have been reduced to just a few pairs by 1989, and predation by feral dogs is perceived as the main threat to the species on Bermuda. The white-tailed tropicbird may also be hunted on some South Pacific islands, where its tail streamers have ornamental uses, and is also threatened on the Hawaiian Islands by diseases brought by introduced birds (2) (3).

The white-tailed tropicbird is protected by law at most key breeding sites, and has benefited from a number of conservation measures. On Bermuda, artificial nesting sites have been built into the sides of quarries, increasing the amount of available nesting habitat, while a dedicated campaign to remove rats in Puerto Rico by trapping and poisoning has seen a significant increase in breeding success in the white-tailed tropicbird. This species would also benefit from further studies into its ecology, abundance and distribution when at sea (3). 

For more information on the white-tailed tropicbird, see:

To find out more about conservation in Bermuda, see:

Authenticated (28/07/2010) by David S. Lee, Director, The Tortoise Reserve, White Lake, USA.
http://www.tortoisereserve.org/ 
http://www.wicbirds.net/

  1. IUCN Red List (June, 2010)
    http://www.iucnredlist.org/
  2. del Hoyo, J., Elliott, A. and Sargatal, J. (1992) Handbook of the Birds of the World. Volume 1: Ostrich to Ducks. Lynx Edicions, Barcelona.
  3. Lee, D.S. and Walsh-Mcgehee, M. (1998) White-tailed tropicbird (Phaethon lepturus), The Birds of North America Online. Cornell Lab of Ornithology, Ithaca.
  4. Perrins, C. (2009) The Encyclopedia of Birds. Oxford University Press, Oxford.
  5. Neotropical Birds (June, 2010)
    http://neotropical.birds.cornell.edu/portal/species/overview?p_p_spp=106556
  6. BirdLife International (June, 2010)
    http://www.birdlife.org/datazone/species/index.html?action=SpcHTMDetails.asp&sid=3650&m=0
  7. West Indian Breeding Seabird Atlas (July, 2010)
    http://www.wicbirds.net/