The members of this order present but a very distant resemblance to the swimming birds described in the preceding pages, from which they differ not only in the construction of their feet, but in their general appearance and peculiar habits.

The birds belonging to this division are characterised by having their body considerably elongated, their neck of moderate length, the head small, and the wings long and rounded or very long and pointed. The tail is variously constructed, but always peculiar and very pointed; and invariably there is between the branches of the under jaw a naked, more or less pouch-like, fold of skin. The tarsus is short and the toes long in correspondence with the great size of the web which connects all the toes with one another, a character whereby they are particularly distinguishable. The general plumage is thick; in some instances compact and stiff, but in others of silky softness. Its colour occasionally differs in the two sexes, and varies much at different ages.

The oar-footed races may all be called inhabitants of the sea, although but a single family is so decidedly oceanic that it never absents itself from the water. All the others willingly prolong their flight far inland, where many of them establish settlements; indeed, there are certain races that only exceptionally visit the sea at all; nevertheless, when they do find themselves in that element they are quite at home, and not only care little for the land, but are able to dispense with fresh water. Some of them at certain intervals come on shore to rest themselves or to sleep on rocky islands and coasts; others prefer a shelving shore; and others, whenever they get an opportunity, roost upon trees: certain species, indeed, might almost be considered true forest birds. In northern climates, as their breeding-time approaches, many of them migrate with great regularity; but in low latitudes they only remove hither and thither, northwards or southwards, following the windings of the sea-coast.

Their nests are generally built either upon trees or in fissures of rocks, sometimes upon ledges of cliffs or on the tops of mountains; less frequently on the little islands met with in marshes and swamps. Wherever their breeding-place may be, they are generally indebted to other birds for relieving them of a considerable share of the labour of nest-building, often contenting themselves with adding materials to their deserted domiciles. Some of them lay but a single egg, others two, others four; the eggs are small, of elongated shape, and generally covered with a calcareous deposit which obscures the markings on the shell. Both parents assist in the work of incubation, and some species would seem frequently to produce two broods in the course of the breeding season. Most of these birds feed exclusively upon fishes; some will occasionally devour small quadrupeds, molluscs, and worms, but fishes invariably constitute their ordinary diet. Some of them catch their food by sailing over the water at a little distance above the surface, whence they suddenly plunge into the water beneath; some swim upon the sea like Ducks, and seize their prey in shallow water by means of their long necks; whilst others again, after the manner of the real divers, pursue their prey to a considerable depth. They are terribly destructive to fishes, and are, consequently, everywhere regarded and treated as enemies by all fishermen.

The TROPIC BIRDS (Phaëton), "Children of the Sun," as they were called by Linnæus, always warn the mariner by their presence that he has entered the precincts of the torrid zone, beyond which they seldom stray. The characteristic features of these beautiful creatures are the small size and