Red-billed Tropicbird
Phaethon aethereus
红嘴鹲
Introduction
A tropicbird species, one of three closely related seabird species inhabiting tropical oceans. It ranges across the tropical Atlantic, eastern Pacific, and Indian Oceans, breeding on isolated islands and cliff faces. The species has three subspecies: P. a. aethereus in the southern Atlantic, P. a. mesonauta in the eastern Atlantic, eastern Pacific, and Caribbean, and P. a. indicus in the Indian Ocean and Middle East waters. Most distinctive traits include white plumage with black barring on the back and wings, a black mask, and tail streamers approximately twice the body length. Originally described by Carl Linnaeus in the 1758 10th edition of Systema Naturae. Classified as least-concern by the IUCN, though populations are declining due to predation by invasive species and environmental threats. Considered threatened in Brazil and Mexico.
Description
A medium-sized seabird measuring 90-105 cm in total length, including the distinctive 46-56 cm tail streamers. Without streamers, the body measures approximately 48 cm. The wingspan ranges from 99-106 cm. It has a tern-like shape with predominantly white plumage, black wing tips, and a back finely barred in black. The black mask extends from above the lores to the sides of the nape with gray mottling. Underparts are white with black markings on the outermost primaries and tertials. The bill is red, legs are orange-yellow at the base with black feet, and the iris is blackish-brown. Males are generally larger than females with tail streamers approximately 12 cm longer. Chicks hatch with gray down and juveniles lack tail streamers.
Identification
Distinguished from other tropicbirds by its red bill combined with white tail streamers. The red-tailed tropicbird has red tail streamers and is slightly smaller, while the white-tailed tropicbird is smaller still, has a black stripe along the upper wing coverts, and an orange-yellow bill. Juvenile red-billed tropicbirds have more heavily barred upper parts than juveniles of other species. In flight, confusion is possible with the royal tern, but the tern lacks tail streamers and has a less direct flight pattern. The subspecies differ in size, plumage coloration, and mask extent.
Distribution & Habitat
Ranges across the tropical Atlantic, eastern Pacific, and Indian Oceans—the smallest range of the three tropicbird species. The nominate subspecies breeds on Atlantic islands south of the equator including Ascension, Saint Helena, Fernando de Noronha, and the Abrolhos Archipelago. P. a. mesonauta occurs in the eastern Atlantic, eastern Pacific, and Caribbean, having colonized the Canary Islands in the 21st century. P. a. indicus inhabits waters off Pakistan, western India, Sri Lanka, the Horn of Africa, and Arabian Peninsula, with rare records in Seychelles. Non-breeding dispersal extends to the 45th parallel north off Washington State and 32nd parallel south off Chile. Vagrant records exist from Great Britain, Australia, Hawaii, and eastern Canada.
Behavior & Ecology
Feeds primarily on fish and squid, usually 10-20 cm long, caught by diving from the air into water from heights up to 40 meters. Often forages alone, though it may follow surface-feeding predators like dolphins and tuna. Flying fish are particularly preferred. Reaches speeds of 44 km/h when flying, cruising at least 30 meters above the sea. Cannot walk proficiently and requires unobstructed takeoff from land. Breeding occurs on isolated cliff faces in loose colonies, with a single egg laid in a simple scrape nest. Incubation lasts 42-46 days by both sexes. Chicks fledge in 10-15 weeks and receive no post-fledging care. Calls only near breeding colonies, joining groups of 2-20 adults in making loud kreeeee-kreeeee-kri-kri-kri-kr screams. First breeding typically at five years.
Conservation
IUCN least-concern status with an estimated 3,300 to 13,000 mature individuals globally and a range of 86.3 million square kilometers. Western Atlantic population: 4,000-5,000 pairs in 2000. Population declining due to human environmental exploitation and predation by invasive species. Main threats include brown and black rats that raid nests for eggs and young, and feral cats that prey on breeding adults. Egg shell thinning from pollutants and reduced hatching success during hot weather (35% versus normal 75%) also impact populations. The species experienced a population bottleneck 450-750 years ago, resulting in low genetic diversity. Considered threatened in Brazil and Mexico.
Culture
Appeared in error on the $50 Bermudian dollar banknote until replaced in 2012 by the white-tailed tropicbird. Alternative common names include bosun bird or boatswain bird, derived from its call resembling a boatswain's whistle, or from the tail feathers' resemblance to marlin spikes. Local West Indian names include truphit, trophic, white bird, paille-en-queue, paille-en-cul, flèche-en-cul, and fétu. American ornithologist Waldo Lee McAtee proposed the name barred-backed tropicbird in 1945 based on its distinguishing black barring.
Source: Wikipedia · CC BY-SA 3.0
Taxonomy
- Order
- Phaethontiformes
- Family
- Phaethontidae
- Genus
- Phaethon
- eBird Code
- rebtro
Subspecies (3)
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Phaethon aethereus aethereus
breeds Fernando de Noronha, Abrolhos Islands, Ascension, and St. Helena islands (southern Atlantic)
-
Phaethon aethereus indicus
breeds coastal Red Sea, Gulf of Aden, Socotra, off Somalia, off eastern Arabian Peninsula, and Persian Gulf; also Con Dao Islands (off Vietnam); winters northeastern Indian Ocean to western Indian coast
-
Phaethon aethereus mesonauta
in eastern Atlantic, breeds Cape Verde Islands and off Senegal, in eastern Pacific, islands in Gulf of California, and off western Mexico, Colombia to Chile, Galapagos; in Caribbean, Puerto Rico to Lesser Antilles, Tobago, and islands off northern Panama and off Venezuela
Data Sources
Species description from Wikipedia, licensed under CC BY-SA 3.0.
Taxonomy data from AviList 2025.