CHARACTERS OF BIRDS 61 



head, then the crown ; next in order come the occiput or poll, the nape, the neck, 

 the back, and — at the lower end — the rump from which the tail feathers arise. On 

 the under side follow the chin, the throat, the breast, and the abdomen, ending 

 with the under tail-coverts. In order to keep the contour-feathers in proper 

 condition, a bird lubricates them with the secretion of the oil-gland placed at the 

 root of the tail. This is a fatty substance, with which the bird first anoints its 

 beak, and then its feathers by passing its beak along them one at a time ; this 

 is more frequently the case with water-birds which have a well-developed oil- 

 gland, but many species, especially such as can only walk, are without this 

 gland. All birds moult at least once a year; a few, like quail, ducks, and 

 certain others, twice in the year, in autumn and in spring. Generally the wing 

 and tail feathers fall off gradually, but ducks and geese sometimes cast them so 

 quickly that they cannot fly at all for a short time. 



Besides the feathers and beak, the length and feathering of the legs and the 

 formation of the feet are of great importance in classifying birds. The hind-limb 

 consists, as in mammals, of the thigh, of the lower half of the leg, and the foot. 

 The short thigh is close to the body, and so well covered with feathers that the 

 knee hardly ever appears ; the lower half of the leg, as in the case of the horse, being 

 often mistaken for the thigh, and the joint of the heel for the knee. The long 

 segment between the heel and the toes is the tarsus, or, properly speaking, tarso- 

 metatarsus. Birds walk only on their toes, and the number and position of these 

 are important. Most birds have three toes in front, corresponding to the second, 

 third, and fourth toes of man and other mammals, which are also denominated in 

 the same way as second, third, and fourth toe, and a hind or first toe, corresponding 

 to the great toe of mammals. Inferences may be drawn regarding the life-history 

 of a bird rather from the formation of its feet than from the nature of its wings, 

 for, with comparatively few exceptions, all birds are good flyers. 



The food of birds varies greatly ; everything produced by a plant, save wood, 

 may serve them for nutriment, while animals of nearly all kinds form the prey of 

 some groups of birds. On the nature of the food depends the habitat of the bird ; 

 hence a vast number are dwellers in the woods, while others frequent treeless 

 plains, and others marshes, or the water. The nesting, again, depends on the stations 

 birds occupy. The eggs of some species, although very few, are not incubated at all, 

 but heated by decaying plants ; the eggs of others, such as the ostrich, are incubated 

 by the males alone. In some cases male and female sit alternately ; in others the 

 male provides the female with food during incubation, and in others again the male 

 leaves all the family cares to the female. The females of the cuckoo and many of 

 its relatives seem to live with several males, a circumstance apparently connected 

 with their parasitical nesting-habits. Many cuckoos, indeed, make no nest at all, 

 but deposit their eggs in other nests. Generally the nest is made by the female, 

 sometimes with the assistance of the male ; and nests are usually found singly, 

 sometimes in great numbers, and in a few cases contain the eggs of several 

 females. 



Young birds that leave the egg almost blind or naked, and are fed by their 

 parents until they are partly feathered, remain in the nest a considerable time, but 

 those that are hatched with their eyes open, and covered with down or feathers, 



