Most adults have tail streamers that are about two times their body length, with those in males being generally longer than those in females.

Whether the egg hatches or not can be influenced by pollution and weather, although the latter has a minimal effect on whether a chick fledges or not.

Birds of all ages feed on fish and squid, catching them by diving from the air into the water.

In some areas, introduced black and brown rats raid nests for eggs and young.

This bird is considered to be a least-concern species according to the International Union for Conservation of Nature (IUCN), though populations are thought to be declining.

English naturalist Francis Willughby wrote about the red-billed tropicbird in the 17th century, having seen a specimen held by the Royal Society.

[6] Local names used in the West Indies include "truphit", "trophic", "white bird", "paille-en-queue", "paille-en-cul", "flèche-en-cul", and "fétu".

[7] In a 1945 paper, American ornithologist Waldo Lee McAtee proposed it be called the barred-backed tropicbird after its most distinguishing feature.

[22] The red-billed tropicbird usually only calls near breeding colonies, where it joins in with groups of other adults, numbering from 2 to 20, in circling above the sea and making loud, harsh kreeeee-kreeeee-kri-kri-kri-kr screams.

If disturbed at the nest, the chicks will vocalize a loud and piercing shriek, either rasping or reeling.

The nominate subspecies Phaethon aethereus aethereus breeds on islands in the Atlantic south of the equator, including Ascension, and Saint Helena on the Mid-Atlantic Ridge, and Fernando de Noronha and Abrolhos Archipelago in Brazilian waters.

[24] The Indian Ocean subspecies, P. a. indicus is found in waters off Pakistan, western India, southwestern Sri Lanka,[25] the Horn of Africa and Arabian Peninsula.

[7] Breeding in the Western Palearctic occurs on the Cape Verde Islands and the Îles des Madeleines off Senegal.

Researchers Larry Spear and David Ainley estimated the minimum population of the Pacific at around 15,750 birds in 1995 after 15 years of field observations.

[31] It sometimes wanders further, including five records from Great Britain,[32] and two from Australia: October–December 2010 on Lord Howe Island and September 2014 on Ashmore Reef.

[20] In July 2005, one was found in eastern New Brunswick, Canada, while another has been seen at Matinicus Rock, Maine regularly since 2000.

[10] For example, for islands in the California Current, breeding starts in November or December, while it occurs year round in the Galápagos.

[15] The courtship displays include flying in the air which takes the form of gliding interspersed with short periods of rapid wing-beating.

They have also been recorded taking over nests of white-tailed tropicbirds and raising their young if they failed to destroy their eggs.

[31] This tropicbird usually lays a clutch of one white buff to pale purple egg with reddish-brown spots.

The egg usually measures 45 by 60 millimeters (1.8 by 2.4 in) and weighs around 67 grams (2.4 oz)—10% of the adult female's weight.

[36] Born helpless and unable to move around (nidicolous and semi-altricial),[39] the chicks are constantly brooded by the parents until they are 3 to 5 days old, when they can thermoregulate their body temperature.

[37] As they grow, the chicks are fed increasingly larger quantities of fish and squid by their parents,[19] generally partly digested and regurgitated.

[10] It usually forages in warmer waters, though does hunt in areas of cooler currents such as the Gulf of California.

[45] Accurate assessment of red-billed tropicbird numbers is difficult due to the remote locations of nesting sites and vast areas of the sea where they might be found.

[46] The population is declining, mainly due to human exploitation of the bird's environment and predation by invasive species,[1] such as rats.

[47] It is estimated that this bird experienced a population bottleneck about 450 to 750 years ago, likely due to exploitation by humans.

[49] On Ascension Island, the effect of the eradication of feral cats was the increase of the red-billed tropicbird population there by about 1.6% in a year.

[50] On the Galápagos Islands, the short-eared owl (Asio flammeus) occasionally eats young birds.

[36] Most egg and chick mortality during periods of normal climate is caused by nest fights between the parents and other birds.