The Tropic-birds, or “boatswains,” as they are often called by the sailors, number six or seven forms, some of which are occasionally found in the United States. They have a compressed, pointed, and slightly curved bill, with the cutting edges of the mandibles serrated. In color the bill is yellow, orange, or coral-red, the wings are long and rather narrow, and the tail of twelve to sixteen feathers, of which the middle pair are greatly elongated and attenuated. The general color of the plumage is white or pinkish throughout, and very soft and satiny in appearance.
In general appearance the Tropic-birds are quite suggestive of Terns, although distinguished at once by the elongated middle, instead of lateral, tail-feathers. From the Frigate-birds, their companions of the deep, they are distinguished by the color of the plumage, the shape of the bill, the absence of a bare spot about the eyes and no throat sac, as well as by the elongated middle tail-feathers.
The Tropic-birds are strictly birds of the ocean and are often seen hundreds of miles from land. Not infrequently when thus far from shore they come, in a more or less exhausted state, to find rest in the rigging of a ship. Although they fly for great distances their flight is not the easy, graceful motion of, for instance, an Albatross, but consists of “regular and rather rapid strokes of the wing, without any apparent intermission.” Their food consists largely of fish which they capture by dashing perpendicularly into the water after the manner of the Terns. The Tropic-birds make no nest or but a slight one and deposit their single egg in holes or crevices in rocks, occasionally in a hollow tree or on the bare sand. The egg is about 2.10 X 1.55 inches, “dilute claret-brown or whitish speckled, sprinkled, spotted, or blotched with deep claret-brown.” The birds during incubation sit closely and fearlessly, allowing themselves to be pushed aside or taken in the hand with no more of protest than a sharp stroke with the bill or a hoarse cry; both sexes take part in incubation.
Perhaps the best-known species is the Red-billed Tropic-bird (P. Aethereus) of the tropical portions of the Pacific and Atlantic oceans, coming north on the Pacific coast to Lower California, and accidentally as far north as the Newfoundland Banks on the Atlantic side. It is nearly forty inches in length, with the central tail-feathers about twenty-six inches long. The bright coral-red bill, the satin white plumage, the elongated tail-feathers, which are snow-white with black shafts, make this a very beautiful bird. The Yellow-billed Tropic-bird (P. americanus) is a smaller species, only about thirty inches long, found on the east coast of North America from Bermuda to the West Indies. It is occasion-ally seen on the Florida coast and may be known at once by the yellow bill and the pinkish, black-shafted middle tail-feathers. The Red-tailed Tropic-bird (P. Rubicaudus), normally of the South Pacific and Indian oceans, though occasionally taken as far north as Lower and southern California, has the middle tail-feathers carmine with black shafts. Mr. W. K. Fisher, who has enjoyed exceptional opportunities of studying it in one of its best-known breeding centers on Laysan Island, writes of its habits as follows: “It nests under the shelter of bushes and not infrequently several will congregate beneath colonies of Fregata aquila, occupying the ground floor as it were. The bird has a vicious temper, and if one attempts to disturb or to take it from the egg, it sets up a horrible and discordant screaming, which soon grows unbearable. The sharp beak with serrated edges is not to be despised, and the enraged bird will sometimes use it to good advantage. The Bow’s’n-birds keep up their strident cries so long as one meddles with them, but if left undisturbed will soon quiet down. Whenever we inadvertently passed near one hidden under a chenopodium bush, we soon became aware of its presence by its cry of defiance. To see these birds at their best one must watch them flying about in the bright sunshine, when their pale, salmon-pink plumage shines as though burnished, and the satiny feathers stand out like scales. The two long, red tail-feathers are possessed by both sexes, and the female is only a trifle less pink than the male. Usually when flying about they were quiet, and progressed by short, nervous wing-beats, never attempting to sail. Occasionally, however, they swooped about our heads and made the neighborhood lively. The nest is merely a hollow in the sand, with a few grass straws and leaves gathered in the bottom. The single egg is brooded by both parents, each of which sits upon it with the wings slightly opened.” The Yellow Tropic-bird (P. Fulvus) has the general color of the plumage, a rich salmon inclining to orange. It is found only about Christmas Island, in the Indian Ocean, where of its habits Mr. C. W. Andrews writes as follows: “The flight of these birds is swift, though, owing to the rapidity of the strokes of the wing, it seems as if they were laboring. I never saw them sail except for a short distance when wheeling around. On hot days they may be seen in twos and threes, flying rapidly up and down above and among the tree-tops, continually uttering their peculiar cackling cry, and pausing now and then to hover before holes in the trees which seem to offer an eligible position for a nest. It can hardly be said, however, that they make a nest, for the single, dark brown mottled egg is merely placed in a slight hollow on the floor of a hole in a tree or in the sea cliff.”