These birds are well known to navigators as the harbingers which foretell the approach to the Tropics. They are distinguished by two long, slender tail-feathers, whence their French name of Paille-en-Queue. They are gifted with great length of wing, which, with their feeble feet, proclaims them formed especially for flight. They are accordingly swift and untiring on the wing, heedlessly going far out to sea; forming, as Lesson remarks, a well-defined and purely geographical group, their homes being in rocky islands, to which they usually return every night. Nevertheless, he frequently met with them in sea-tracks far from any land, possibly they having been swept, by the sudden squalls and hurricanes so frequent in equatorial seas, beyond their natural limits. [Illustration: Fig. 101.--Tropic Bird (_Phaeton æthereus_, Linn.).] The Common Tropic Bird, _Phaeton æthereus_, seems to confine itself, according to this writer, to the Atlantic Ocean, stopping on the confines of the Indian Ocean; the other species, _Phaeton Phoenicurus_, seeming to belong further eastward, both meeting in nearly equal numbers at the Mauritius and other islands of the same group. Their flight is described as calm, quiet, and composed of frequent strokes of the wing, interrupted by sudden falls. The bird is about the size of a Partridge, with red bill and markings under the lower mandible; in general appearance it resembles the Gulls, but has longer and more powerful wings; the legs and feet are vermilion red, the latter webbed; the tail has two long, narrow feathers. One of their breeding-places is the Bermudas, where the high rocks which surround the island are a protection from the attacks of the fowler. _P. Phoenicurus_ is a larger bird, being thirteen inches from the bill to the root of the tail; the long tail-feathers being red of the deepest hue. The appearance of this bird announces, as we have said, that the navigators have entered the torrid zone, as this bird rarely goes beyond the limits of this region. It sometimes, however, pushes out to sea to a distance of a hundred leagues. When they are fatigued, aided by their large webbed feet, they rest upon the waves. Like many other ocean birds, their peculiar organisation prevents them settling from choice on the ground. They are, therefore, compelled to skim continually over the water, in which they feed upon the fish and mollusks, which form their principal food. When they are on the shore, the immense spread of their wings induces them to choose some elevated spot for a perch, such as the top of a tree or the summit of a rock. Worn out by fatigue, if they settle on the water, they are forced to wait until they are lifted up on the crest of a wave before they can again take flight. Their mode of flying is rather curious, for they communicate to their wings a kind of quivering motion, as if overcome by exhaustion.