Tropic birds are three species of pan-tropical sea-birds that make up the family Phaethontidae, in the order Pelecaniformes, which also includes the pelicans, anhingas, cormorants, gannets, and boobies.
Tropic birds are medium-sized seabirds, weighing about 0.9 lb (0.4 kg), and having a body length of 16-18.9 in (41-48 cm). This length does not include their greatly elongated tail feathers, which are shaped as streamers that themselves can be 21 in (53 cm) long. The wings of tropic birds are short, stout, and pointed, and their legs are short and their feet small, with the toes completely webbed. Their beak is stout, pointed, and slightly down-curved, with serrated edges to help hold on to their slippery prey of fish or squid.
The usual coloration of the body is white, with black markings on the head and wings. The bill is colored either bright red or yellow, and the tail-streamer is still prized by various Polynesian cultures. These streamers are either white or red, depending on the species. The sexes are alike in size and coloration.
Tropic birds have a loud, shrill, piercing scream, which is the origin of one of the common names of these birds, the bosun bird. (Bosuns or boatswains are ship petty officers, responsible for maintenance of the ship and its gear, and equipped with a loud, shrill whistle, used to catch the attention of sailors.) Tropic birds are strong and graceful fliers, typically exhibiting bouts of fluttering, pigeon like wing-strokes, punctuated by short, straight glides and soaring flights. Tropic birds do not swim well, and they float with their tail held in a cocked, erect position. These birds are extremely awkward on land and can barely walk.
Tropic birds feed using partially closed-winged, aerial plunge-dives to catch their food of small fish or squid near the surface. They can even catch flying fish, while the fish are in the air. Tropic birds generally occur as solitary birds in off-shore, pelagic waters outside of their breeding season. They may, however, mix with large, feeding flocks of other species, such as shearwaters and terns.
The courtship of tropic birds involves the potential pair engaging in graceful, aerial wheelings and glides, with loud cries. Occasionally one bird will hover over the other, touching it with the tip of its tail-streamer. Tropic birds lay their single egg in a simple scrape in a hidden cavity on a rocky, near-shore cliff, or sometimes under a bush. Both sexes incubate the egg, and they share in guarding and feeding their white-downy, young chick. Juvenile birds leave their birth island as soon as they can fly, and return when they reach sexual maturity. Tropic birds may breed throughout the year.
The red-billed tropic bird (Phaethon aethereus ) occurs in the tropical Caribbean, Atlantic, eastern Pacific, and Indian Oceans. The tail-streamer of this species is white, and the upper parts of its body are barred with white and brown.
The red-tailed tropic bird (P. rubricauda ) occurs in the tropical Indian and Pacific Oceans, but in different regions of those oceans than the red-billed tropic bird. The red-tailed tropic bird has a bright-white body and a red streamer.
The white-tailed or yellow-billed tropic bird (P. lepturus) occurs in all of the tropical oceans. This smallest tropic bird has a white body, with black patches on its wings and back, a relatively small, yellow beak, and a white streamer.
None of the tropic birds breed in North America. However, all species are rare visitors to coastal waters of the southern United States, especially after a heavy wind-storm. The red-billed tropic bird is a regular but rare bird off southern California, while the white-tailed tropic bird occurs off the southeastern states in the warm Atlantic, Gulf of Mexico, and Caribbean. The red-tailed tropic bird is a very rare visitor to southern California.
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