HOW BIRDS COMPARE
WITH MAMMALS
In some ways birds are the highest of the vertebrate animals. They represent the climax of that passage from water to land which the backboned series illustrates. Their skeleton is more modified from the general type than that of mammals; their arrangements for locomotion, breathing, and nutrition are certainly not less perfect; their body temperature, higher than that of any other animals, is an index to the intense activity of their general life; their habitual and adaptive intelligence is familiarly great, while in range of emotion and sense impressions they must be allowed the palm. It is, in fact, only when we emphasize the development of the nervous system and the closeness of connection between mother and offspring, that the mammals are seen to have a right to their pre-eminence over birds.
THE VOICE OF
BIRDS
With few exceptions, birds have a vocal organ, and are able to produce more or less variable sounds. The organ is, however, wanting in the running birds, such as the ostrich, and in the American vultures. The sounds produced are almost as varied as the different kinds of birds, and an expert has little difficulty in identifying a great number of forms by their distinctive noises. It is among the so-called perchers, songsters, or Insessores, that we find song really developed and that for the most part in the males, and in highest degree at breeding-time.
HOW BIRDS ARE
CLOTHED
The integument differs markedly from that of other animals in being clad with feathers. Three distinct kinds of feathers are at once distinguishable—(a) the small hair-like downy rudimentary filoplumes; (b) the numerous smaller contour or covering plumes; and (c) the large strong quill-feathers or pennæ on wings and tail. The ordinary feather consists of a quill at the base of a shaft up the center, and of the vane borne on the sides of the shaft. The vane consists of parallel barbs, which are linked together by small barbules. On the bare legs of many birds the feathers are replaced by horny scales, and the horny structures forming the beak and terminating the toes are very familiar.
THE BIRDS OF PREY
The birds of prey have a hooked, curved beak, at the base of which are the nostrils, surrounded by cere skin. They live chiefly upon warm-blooded animals, which they seize with their claws and tear in pieces with their beak. There are more than five hundred varieties, which are separated into day and night birds of prey.
Eagles, falcons, hawks, harriers, buzzards, and the like are adapted for the pursuit of prey not only by possession of strong, hooked beaks, powerful talons, and keen powers of vision, but also by the swiftness of their flight. Many of them—for example, falcons—are able to poise themselves, apparently motionless, in the air till some such prey as a young rabbit or small bird is discovered, and then swoop down upon the victim with almost incredible rapidity.