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Red-billed Tropicbirds – Two Long Streamers and a Bad Lipstick Job

Red-Billed Tropicbirds have always reminded me of my great aunt Sue. A bit heavy handed with bright red lipstick.  If the size and color of their bills fails to catch your attention, look at their tails. The adults have two long center tail feathers that double their overall length.  From your cockpit, an adult tropicbird will appear as a mostly white bird with a chunky body and very fast wing beats with two very long feathers streaming from their tails.

There are two species of tropicbirds in the Caribbean and a third (Red-tailed Tropicbird) that occurs in the Pacific Islands.  The tropicbird we see most often in the Lesser Antilles (the Leeward and Windward Islands) is the Red-billed Tropic bird. The smaller White-tailed Tropicbird is most often seen in the Greater Antilles, Bahamas, and Cayman Islands, but does overlap in range Red-billed Tropicbird. The Red-billed Tropicbird occurs in the tropical Atlantic, eastern Pacific and Indian Oceans.

The adult Red-billed Tropicbird is mostly white with a long horizontal teardrop-shaped eye stripe with fine black barring on its back and black outer primaries on the wing. Males and females have the same plumage and are about the same size. Immature Red-billed Tropicbirds have less distinct barring on the back, lack the long tail feathers and its bill is more orange than red.  The adult Red-billed Tropicbird has an 18-20 inch body with a tail equally as long as their bodies.

Their bills are large, powerful and slightly decurved. Their heads are large and their necks are short and thick. Like other members of their order, their feet are totipalmate (that is, all four toes are connected by a web). The legs of a tropicbird are located far back on their body, making walking impossible, so that they can only move on land by pushing themselves forward with their feet.  They come to land only for nesting purposes and may be seen hopping about, as they are so poorly equipped for walking.

It is hard to watch tropicbirds for very long with out asking why they have such long tail feathers.  It seems reasonable that they are important for flight or diving, but extensive research on Red-tailed Tropicbirds in Hawaii has shown that the streamers are ornamental rather than an aerodynamic function.  The red bills are likely also for courtship and may be an aid for the young chicks to focus on their parents bills for feeding.

Tropicbirds catch their prey by hovering and then plunge-diving from 100 plus feet. They eat mostly fish, especially flying fish. Tropicbirds tend to avoid multi-species feeding flocks with Brown Boobies and Magnificent Frigatebirds. Some researchers have proposed that since Red-billed Tropicbirds characteristically plunge from higher altitudes and are less maneuverable, they might face too much interference from a swirling flock of birds beneath them. Tropicbirds are usually seen alone or in pairs away from breeding colonies.  As in many diving seabirds, a network of tiny air sacs beneath the skin of the foreparts cushions the impact of the dive.

Tropicbirds generally nest in holes or crevices on the bare ground or rocky cliffs. Near the breeding sites they engage in spectacular courtship displays. For several minutes, groups of 2–20 birds simultaneously and repeatedly fly around one another in large, vertical circles, while swinging the tail streamers from side to side. Occasionally one bird will hover over the other, touching it with the tip of its tail-streamer. If the female likes the presentation, she will mate with the male in his prospective nest-site.

The female will lay one egg which will be incubated for 40-46 days. The incubation is performed by both parents but mostly the female, and the male will bring her food while she incubates the egg. The chick has grey down and will stay alone in nest while both parents search for food until fledging, about 12-13 weeks after hatching. The young are not able to fly initially; they will float on the ocean for several days to lose weight before flight. Tropic birds have a loud, shrill, piercing whistle, which is the origin of one of the common names of these birds, the bosun bird.

The greatest threat to all of the species of tropicbirds and many other seabirds is non-native mammalian predators such as rats and mongooses that eat the eggs or chicks at the nesting colonies. 

Devi Sharp is a retired wildlife biologist and is exploring the birds of the Caribbean with her husband, Hunter on their sailboat, Arctic Tern.

Chuck Shipley is a former professor of computer science and an avid amateur photographer.  He and his wife Barbara live aboard their trawler, Tusen Takk II, in the Caribbean.

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