Red-billed tropicbird

Red-billed tropicbirds live over warm, tropical seas.

They come to small islands and cliffs to nest.

Red-billed tropicbirds live over warm tropical seas in the Atlantic Ocean, the Caribbean, the eastern Pacific and the north-west Indian Ocean. They spend most of their lives at sea.

They come to land to nest, on small, remote islands and on cliffs. Big colonies nest on the Galápagos Islands and in the Caribbean. Others nest off Mexico, Chile and Senegal, on Cabo Verde, on islands in the southern Atlantic and on the coasts of Yemen, Oman and Saudi Arabia.

The IUCN describes a mostly pelagic species of tropical and subtropical waters across the Atlantic, the north-west Indian Ocean and the eastern Pacific. Breeding colonies are on the Galápagos Islands (Ecuador), Chañaral Island off Chile, off the Pacific coast of Mexico, in the Caribbean, on Cabo Verde, on southern Atlantic islands, off Senegal and on the coasts of Yemen, Oman and Saudi Arabia (del Hoyo et al. 1992, Diop et al. 2019).

No regular migration is known, but individuals can disperse widely out to sea. Kaufman (Audubon, 1996) calls it common in parts of the Caribbean; off North America it is the only tropicbird likely to be seen off California, though rare there, and it very rarely strays to waters off Florida. The IUCN country list also includes many places where it turns up only as a vagrant.

Red-billed tropicbirds eat small fish and squid.

They dive into the sea from the air to catch them.

Red-billed tropicbirds eat mainly small fish, especially flying fish, and also squid. Most food is caught by plunge-diving: the bird dives into the sea from the air. Flying fish are sometimes caught in the air.

On the Caribbean island of St. Eustatius, flying fish made up more than half of the food samples that scientists collected at nests. Birds tracked there with GPS went up to 953.7 kilometers from their colony to find food.

The IUCN gives small fish, especially flying fish, and squid as the diet, taken mainly by plunge-diving, with flying fish sometimes caught in flight.

Madden et al. (2022, Marine Ornithology; listed by the USGS) sampled regurgitated food at nests on St. Eustatius, Lesser Antilles, and GPS-tracked adults in early chick rearing. Flying fish (Exocoetidae, 59.5%) and Belonidae (14.9%) dominated the samples, and 25.5% could not be identified. Birds foraged by day, and where they foraged the water was deeper, with higher chlorophyll concentrations, than where they were just travelling. Average trips were 176.8 kilometers long, and the farthest a bird went from the colony was 953.7 kilometers. On St Helena, GPS-tracked birds made trips of 1,000 to 2,000 kilometers, going as far as 400 to 750 kilometers from the colony (S. Oppel, cited by the IUCN).

Tropicbirds call with a loud rattle as they fly.

Many tropicbirds nest in the same place, in loose groups.

Red-billed tropicbirds give a loud, rattling call while they fly. They nest in loose colonies. On Saba, scientists found adults at their nests guarding an egg or a chick.

Away from the nest, they roam the open sea. They do not make regular migrations, but some birds spread far out over the ocean. Scientists have put GPS trackers on some birds to see where they go to find food.

Kaufman (Audubon, 1996) describes a loud rattling call given in flight. The IUCN calls the species loosely colonial and congregatory but dispersive, with no regular migration known.

On Saba, adults at occupied nests were guarding a single egg or chick (The Daily Herald, 2020). Because adults return to their own birth colony and birds rarely move between colonies, the Saba researchers said this isolation makes the species vulnerable to dying out locally, as happened to the white-tailed tropicbird on Saba in the 2000s. GPS tracking on St. Eustatius showed birds crossing multiple exclusive economic zones and marine protected areas, so Madden et al. (2022) suggest that protecting the species may need cooperation across borders in the wider Caribbean.

Rats and cats can find tropicbird nests.

People are working to keep the nests safe.

The red-billed tropicbird is listed as least concern, but its numbers are going down. There are thought to be about 16,000 to 30,000 adults.

On some islands, invasive rats and feral cats take eggs and chicks from nests on the ground. A chick that spends about three months in a ground nest is easy for them to reach. Building houses, roads and sea walls on coasts has also taken away nesting places. By 2019, removing feral cats on Saba had helped chicks survive again.

BirdLife International assessed Phaethon aethereus as Least Concern for the IUCN Red List (assessed 1 August 2019, published 2019): decreasing trend, preliminarily 8,000 to 15,000 pairs (16,000 to 30,000 mature birds). The largest colonies, with several thousand pairs each, are in the Galápagos and the Caribbean; about 1,000 pairs nest along Mexico's Pacific coast.

Threats named by the IUCN: invasive rats taking eggs and nestlings in Abrolhos National Park, Brazil (Sarmento et al. 2014), where laying one egg, a long incubation and easily reached crevices make birds vulnerable; feral cats on Saba, where breeding success was zero at the colonies most exposed to cats against 65% at a colony with less predation (Boeken 2016); and coastal housing, roads and sea walls (Lee and Walsh-McGehe 2000). The IUCN notes that predation affects only a minority of the global population. On Saba, cat culling had a positive effect by 2019, though predation by cats and rats at Old Booby Hill had increased (The Daily Herald, 2020).