Red-tailed tropicbird

Red-tailed tropicbird
Scientific classification
Kingdom Information
Domain	Eukaryota
Kingdom	Animalia
Subkingdom	Bilateria
Phylum Information
Superphylum	Deuterostomia
Phylum	Chordata
Sub-phylum	Vertebrata
Infraphylum	Gnathostomata
Class Information
Superclass	Tetrapoda
Class	Aves
Sub-class	Neognathae
Infra-class	Neoaves
Order Information
Order	Phaethontiformes
Family Information
Family	Phaethontidae
Genus Information
Genus	Phaethon
Species Information
Species	P. rubricauda
Population statistics
Population	>32,000 (1992 est.)
Conservation status	Least concern

The red-tailed tropicbird (Phaethon rubricauda) is a species of pelagic bird of the family Phaethontidae, and found in tropical waters of the Pacific and Indian Oceans.

Description

The red-tailed tropicbird is tern-like in appearance, but larger. It has a body length of 23 to 27 inches from the bill to the short tail feathers; the two streaming tail feathers add another 14 inches to its length. It has a wingspan of 44 to 47 inches, and a weight of 28.2 ounces. Males are slightly larger than females.

It is predominately white in color overall, with a crescent-shaped black eye mask and a strong, slightly downward-curved beak red in color, offset with black around the nostrils. The pair of streaming tail feathers, although thinner than in the other tropicbirds, are red in color and very conspicuous. The upper wings and back bear a very light gray wash, accompanied in some birds by a pink tinge. Several feathers of the secondary coverts on the underside of the wings are tipped in black. Legs are pale-blue, and the webbed feet are black. Chicks are generally light gray in color with black barring on top, and bear a black beak.

The red-tailed tropicbird typically flies high above the water surface, using very regular, almost mechanical, wing beats, as well as using recurrent gliding phases in which it neither gains nor loses altitude. The legs are set very far back on the body and the feet are too weak to carry the body weight. Locomotion on land consists of a belly-crawl involving both legs and wings, until they find a place from which they can take off again.

Subspecies

• Phaethon rubricauda melanorhynchos; tropical Pacific Ocean
• Phaethon rubricauda roseotinctus; southwestern Pacific Ocean
• Phaethon rubricauda rubricauda; western Indian Ocean
• Phaethon rubricauda westralis; eastern Indian Ocean to Pacific Ocean eastward toward Easter Island

Range

Red-tailed tropic birds are primarily seen outside of the breeding season in the tropical Indian and Pacific Oceans, occurring there approximately between 40° S and 40° N. They breed on small islands or coastal areas of larger islands in Mauritius, Madagascar, Seychelles, on islands off Western Australia and Queensland, New Caledonia, Ogasawara guntō, the Kermadec and Society Islands, Easter Island, and Hawaii. Vagrants have occasionally been observed farther inland, and a recent study has confirmed a sighting, but not a breeding colony, on Tristan da Cunha in the south Atlantic Ocean.

Diet

These birds eat mainly fish and cephalopods, caught from a plunge dive as high as 150 feet. The high altitude compensates for the fact that the physique of the red-tailed tropcbird is little streamlined. Occasionally they also catch flying fish in the air. Prey animals are swallowed underwater, or while the bird is sitting on the surface. Red-tailed tropicbirds usually forage alone, but sometimes are associated with other tropicbirds or seabirds.

Breeding

Red-tailed tropicbirds become sexually mature at the age of 3-4 years, and form par-bonds which are monogamous. They breed on tropical islands where they form small colonies with little social interaction. The breeding grounds can be found on inaccessible cliffs or on on sandy shores, where nests can be hidden under vegetation. On Christmas Island and the Kure Atoll, the couple relationship persists over several reproductive periods. They breed either individually or in loose colonies. Nesting density may depend more on suitable breeding sites, ranging from three to six feet or up to 210 feet. Some islands have only one or two nests of red-tailed tropicbirds. So far, it has not been investigated at what age they couple the bond. However, there are some indications from observations on the Kure Atoll that the pairs form a year before the first brood.

Breeding is preceded by a spectacular courtship flight, involving climbing to altitude and diving, with both birds touching wingtips and tail feathers. Afterwards, the couple lands at a suitable nesting site and usually copulates immediately after landing. If the ground permits, a small hollow is dug for the egg. If suitable nesting sites are scarce, fighting for such places can occur, with opponents using their beaks to hack on the heads of each other. If an opponent is successful, the others who had previously nested on the spot must give up their egg or chick. Due to the fighting in some places only 30% of the breeds are successful. Tropicbirds also use this aggressiveness against other species: they sometimes successfully displace petrels and take over their nesting sites.

A single egg, dull light brown in color, is laid. The egg is incubated for 40 to 48 days by both partners. The chick is initially fed with pre-digested food that the parent birds regurgitates into the chick's throat. Over time the chick is left alone more often, with the intervals between feedings increasing, and at about 70 to 90 days of age it makes its first flight and does not return to the nesting site.

The maximum age of tropic birds is unknown, but in any case exceeds sixteen years.

Threats

The ICUN classifies this species as "least concern", emphasizing the large range of the bird and a stable population. However, it does mention a current vulnerability with rats introduced to the islands on which they breed, as well as successful eradication programs.