Red-billed tropicbird

Red-billed 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. aethereus
Population statistics
Population	5,000-20,000 (2018 est.)[1]
Conservation status	Least concern[1]

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

The red-billed tropicbird is tern-like in appearance, but larger. It has a body length of 19 inches from the bill to the short tail feathers; the two streaming tail feathers add another 18 to 22 inches to its length. It has a wingspan of 39 to 42 inches. Males are slightly larger than females.

It is predominately white in color overall, with a black eye mask and a strong, slightly downward-curved beak coral-red in color. The upper wing primary feathers and outer half of the coverts are black; the top of the back to midway on the wings is barred in dark gray to black, depending on the subspecies. Legs are yellow, and the webbed feet are black. Chicks are generally light gray in color with a yellow beak.

Subspecies

• Phaethon aethereus aethereus; South Atlantic Ocean (Fernando de Noronha, Ascension and St. Helena islands)
• Phaethon aethereus indicus; Indian Ocean (Gulf of Aden), Red Sea, Persian Gulf
• Phaethon aethereus mesonauta; Subtropical and tropical eastern Pacific Ocean (off Mexico and area of Galapagos Is.), eastern Atlantic Ocean, Caribbean Sea

Some authorities consider the Galapagos Islands population to be a fourth subspecies, Phaethon aethereus limatus[2].

Red-billed tropicbirds are found in much of the tropical and subtropical regions of the Indian Ocean, the Atlantic Ocean, and the eastern Pacific Ocean. It only comes ashore during the breeding season, nesting on the Cape Verde Islands, Ascension, St. Helena, Fernando de Noronha, Galapagos, the islands off western Mexico and South America, the Gulf of Aden and the Persian Gulf.

Red-billed tropicbirds hunt fish and cephalopods, and usually from a plunge dive into the water from a height of 75 feet or more, capturing prey at or just below the surface. Particularly common are flying fish^[2] and small squid, which can be taken in flight while barely skimming the surface.

Red-billed tropicbirds become sexually mature at the age of 3-4 years. 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.

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 is laid, which is white with a dirty appearance, often purplish with a reddish-brown spotted tinge. The egg is incubated for 40 to 46 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 is unknown, but in any case exceeds sixteen years.

Due to the large range, the ICUN classifies this species as "least concern", meaning the threat to the species globaly is not cause for alarm. Yet, it is the rarest of the three species of tropicbird, with an estimated 20,000 birds worldwide. Most breed on the Central American coasts, with larger populations existing in the Galapagos Islands and the Caribbean. In the Western Palearctic this species is very rare, with only between 100 and 125 breeding pairs breed on the Cape Verde Islands, and a 1993 discovery of a breeding colony in the Azores^[3]. In 2016, a breeding colony of at least eight couples was confirmed for the Canary Islands^[4].

However, man has occasionally impacted nesting sites with either coastal building or road construction, or the introduction of predatory animals. A population of subspecies P. a. aetherus nesting within Brazil's Abrolhos National Park is under siege from introduced rats (Rattus rattus and R. norvegicus), which invade burrows and feed upon chicks and unhatched eggs[3].