The order of the Scansorial or Climbing birds is easily and very shortly defined, having no other distinctive and exclusive peculiarity except the fact that the feet are provided with four toes, of which two are turned backwards and two forwards. Of the two toes 7vhich are directed backwards, one is the hallux or proper hind-toe, and the other is the outermost of the normal three anterior toes. This arrangement of the toes (fig. 342, B) enables the Scansores to climb with unusual facility. Their powers of flight, on the other hand, are generally only moderate and below the average. Their food consists of insects or fruit. Their nests are usually made in the hollows of old trees, but some of them have the remarkable peculiarity that they build no nests of their own, but deposit their eggs in the nests of other birds. They are all monogamous.
Fig. 342. - A, Skull of a Parrot (Psittacus erythacus). B, Foot of the same : a Hallux ; b Index ; c Middle toe ; d Outer or ring toe. (After Blanchard.)
The order Scansores, as above defined, must be looked upon as a. purely artificial assemblage, comprising birds which possess in common the peculiarity of a scansorial foot, but which otherwise are widely different. The order is only retained here because it can hardly be dispensed with otherwise than by raising the three principal groups contained in it to the rank of separate orders (viz., the Cuculidae, Picidae, and Psittacidae).
The most important families of the Scansores are the Cuckoos (Cuculidae), the Woodpeckers and Wry-necks (Picidae), the Parrots (Psittacidae), the Toucans (Rhamphastidae), the Trogons (Trogonidae), the Barbets (Bucconidae), and the Plantain-eaters (Musophagidae).
The Cuculidae, or Cuckoos, are chiefly remarkable for the extraordinary fact that many of them, instead of nidificating and incubating for themselves, lay their eggs in the nests of other birds. The only bird not belonging to this family which has the same "parasitic" habit, is the Cow-bunting (Molothrus pecoris) of the United States. As a rule, only one egg is deposited in each nest, and the young Cuckoo which is hatched from it, is brought up by the foster-parent, generally at the expense of the legitimate offspring. The large Channel-bill (Scythrops Novae-Hollandice) is said to possess the same curious habit, but many species of this group build nests for themselves in the ordinary manner. Beside the typical Cuckoos (Cuculus) this group contains the American Cuckoos (Coccygus), the Anis (Crotophaga), the Honey-guides (Indicator), and other less important forms.
The second family of the Scansores is that of the Picidae, and comprises the Woodpeckers and Wry-necks. These birds feed chiefly upon insects, and the tongue is very extensible, barbed at the point, and covered with a viscid secretion, so as to enable them to catch their prey by suddenly darting it out. The bill is strong and wedge-shaped, and the claws crooked. The tail-feathers terminate in points, and are unusually hard and stiff, assisting the bird in running up the trunks of trees. The Woodpeckers are widely distributed throughout both hemispheres, and the Wry-necks (Yunx) are European.
The next family is that of the Parrots (Psittacidae), the largest group of the Scansores, comprising several hundred species. The bill in the Parrots is large and strong, and the upper mandible is considerably longer than the lower, and is hooked at its extremity (fig. 343). The bill is used as a kind of third foot in climbing, thus allowing the feet to be used in prehension. At the base of the upper mandible is a "cere," in which the nostrils are pierced. The tongue is soft and fleshy. The feet are especially adapted for climbing, some, however, of the. Parrots moving about actively on the ground. The colours of the plumage are generally extremely bright and gaudy; and they live for the most part upon fruits. The Psittacidae are distributed throughout the tropics, and in the southern hemisphere as far south as the 52d parallel. They are monogamous, and make their nests in holes in trees, and in the rocks. Their natural voice is harsh and grating. The true Parrots (Psittacus) are mostly inhabitants of tropical America, and their prevailing colour is green. Other well-known forms are African. The Cockatoos (Plyctolophus), the Love-birds (Agapomis), and the Lorikeets (Trichoglossus) belong to the Melanesian and Australian province. The Lories (Lorius) inhabit the Melanesian province. The true Macaws (Arainae) are exclusively American ; and the true Parrakeets (Pezoporinae) are exclusively confined to the eastern hemisphere, being especially characteristic of Australia.
Fig. 343. - Head of Cockatoo.
Among the more remarkable of the Psittacidae may be mentioned the singular "Kakapo" (Strigops habroptilus) of New Zealand, which makes an approach to the Owls. This curious Parrot differs from the ordinary members of the order in not being gregarious in its habits, in only being active by night, in forming burrows in the ground, in which it spends the day, and in being limited in its powers of flight. One species of Parrot (Lophopsittacus Mauritianus) has become extinct during the human period, and the Philip Island Parrot (Nestor productus), of the New Zealand province, has not been known to occur since the year 1851.
In the next family of the Scansores are the Toucans (Rham-phastidae), characterised by having a bill which is always very large, longer than the head, and sometimes of comparatively gigantic size (fig. 344). The mandibles are, however, to a very great extent hollowed out into air-cells, so that the weight of the bill is much less than would be anticipated from its size.
The tongue is very long, notched at its side, or feathered with delicate lateral processes. The Toucans live chiefly upon fruits, and are all confined to the hotter regions of South America, frequenting the forests in considerable flocks.
The Trogons have short and weak feet, a short triangular bill, the gape bordered with strong bristles, and short wings. The plumage is soft and loose, and generally of the most gorgeous description. They inhabit the most retired recesses of the forests of the intertropical regions of both hemispheres, and show many decided points of affinity to the Goatsuckers.
Fig. 344. - Head of Toucan.
The Barbets (Bucconidae) are South American, but also occur in Africa and in the Indian province. Lastly, the Plantain-eaters or Touracos (Musophagidae) are exclusively confined to Africa.
The range of the Scansores in time does not appear to be extensive, the earliest known representative of the order being from the Lower Tertiary. The Eocene beds of Wyoming have yielded remains of a Woodpecker (Uintornis), and Parrots, Trogons, Cuckoos, and Woodpeckers are known to have lived during the later Tertiary and Post-tertiary periods.