Red-billed Tropicbird

The Red-billed Tropicbird, Phaethon aethereus, is a seabird of tropical oceans, with a striking appearance that includes predominantly white plumage accented by black markings on the wings and back. A distinctive black mask graces its face, and its name is derived from the characteristic red bill. Adult birds boast impressive tail streamers, often twice their body length, with males typically sporting longer streamers than females. This species is further divided into three subspecies, each with subtle variations in size, plumage, and bill coloration.

Identification Tips

When identifying the Red-billed Tropicbird, look for its long white tail streamers and red bill, which set it apart from other tropicbirds. The black mask and gray mottling near the nape are also key features. In flight, the bird's tern-like shape and black wingtips are noticeable. Juveniles lack the tail streamers and have more heavily barred upper parts compared to adults.

Habitat

These tropicbirds favor isolated cliff faces for nesting, often forming loose colonies. They require clear takeoff paths due to their limited walking ability and rely on unobstructed spaces for flight from land.

Distribution

The Red-billed Tropicbird is found across the tropical Atlantic, eastern Pacific, and Indian Oceans. Subspecies are distributed in specific regions: the nominate in the southern Atlantic, P. a. indicus in the Middle East and Indian Ocean, and P. a. mesonauta in the eastern Atlantic, Pacific, and Caribbean.

Behaviour

Capable of reaching speeds of 44 km/h (27 mph) at sea, the Red-billed Tropicbird is an adept flyer but a poor swimmer. It cannot stand well and has a limited walking ability. During the breeding season, these birds engage in elaborate aerial courtship displays and are known to be aggressive at nest sites.

Song & Calls

The Red-billed Tropicbird is vocal near breeding colonies, where it emits loud, harsh "kreeeee-kreeeee-kri-kri-kri-kr" screams. Disturbed chicks produce a piercing shriek as a defense mechanism.

Breeding

Breeding involves a simple scrape nest on a cliff face, with both sexes sharing incubation duties for a single egg over a period of approximately six weeks. Chicks fledge after 10 to 15 weeks, with parental care ceasing shortly thereafter.

Similar Species

The Red-billed Tropicbird can be distinguished from the Red-tailed Tropicbird by its white tail streamers (as opposed to red) and from the White-tailed Tropicbird by its larger size, black upper wing stripe, and yellow-orange bill.

Diet and Feeding

These birds primarily feed on fish and squid, which they catch by diving from the air into the water. They are known to follow surface-feeding predators to capitalize on prey driven to the surface.

Conservation Status

The IUCN lists the Red-billed Tropicbird as Least Concern, though populations are believed to be declining. Threats include habitat exploitation and predation by invasive species such as rats and cats. In some regions, such as Brazil and Mexico, the species is considered threatened.

Threats and Survival

Eggs and chicks are vulnerable to predation by introduced rats and feral cats. Environmental factors like pollution and weather can influence egg hatching success, while adult and juvenile survival rates vary, with adults generally having higher annual survival.