BIRDS IN GENERAL. 



moult; his old feathers fall before their time, 

 and a new set take place, more brilliant and 

 beautiful than the former. They add, that it 

 mends the bird's singing, and increases its 

 vivacity; but it must not be concealed, that 

 scarcely one bird in three survives the opera- 

 tion. 



The manner in which nature performs this 

 operation of moulting is thus : the quill, or 

 feather, when first protruded from the skin, 

 and come to its full size, grows harder as it 

 grows older, and receives a kind of periosteum 

 or skin round the shaft, by which it seems 

 attached to the animal. In proportion as 

 the quill grows older, its sides, or the bony 

 part, thicken ; but its whole diameter shrinks 

 and decreases. Thus, by the thickening of 

 its sides, all nourishment from the body be- 

 comes more sparing ; and, by the decrease of 

 its diameter, it becomes more loosely fixed in 

 its socket, till at length it falls out. In the 

 mean time, the rudiments of an incipient quill 

 are beginning below. The skin forms itself 

 into a little bag, which is fed from the body 

 by a small vein and artery, and which every 

 day increases in size till it is protruded. 

 While the one end vegetates into the beard 

 or vane of the feather, that part attached to 

 the skin is still soft, and receives a constant 

 supply of nourishment, which is diffused 

 through the body of the quill by that little light 

 substance which we always rind within when 

 we make a pen. This substance, which as 

 yet has received no name that I know of, 

 serves the growing quill as the umbilical ar- 

 tery does an infant in the womb, by supply- 

 ing it with nourishment, and diffusing that 

 nourishment over the whole frame. When, 

 however, the quill is come to its full growth, 

 and requires no further nourishment, the vein 

 and artery become less and less, till at last 

 the little opening by which they communica- 

 ted with the quill becomes wholly obliterated; 

 and the quill, thus deprived, continues in its 

 socket for some months, till in the end it 

 shrinks, and leaves room for a repetition of the 

 same process of nature as before. 



The moulting season commonly obtains 

 from the end of summer to the middle of au- 

 tumn. The bird continues to struggle with 

 this malady during the winter ; and Nature 

 has kindly provided, that when there are the 

 fewest provisions, that then the animal's ap- 

 petite shall be least craving. At the begin- 

 ning of spring, when food begins again to be 

 plentiful, the animal's strength and vigour re- 

 turn. It is then that the abundance of provi- 

 sions, aided by the mildness of the season, in- 

 cite it to love, and all Nature seems teeming 

 with life, and disposed to continue it. 1 



1 Prnft'sscr Blumenbach of Gottingen, in his admir- 



CHAP. II. 



OF THE GENERATION, NESTLING, AND 

 INCUBATION OF BIRDS. 



THE return of spring is the beginning of 

 pleasure. Those vital spirits, which seemed 



able Manual of the Elements of Natural History, gives 

 the following description of the characteristic qualities of 

 birds. As a summary of all that can be said on the 

 subject, we consider it to stand unrivalled. With re- 

 gard to form, he says, all birds coincide in having two 

 feet, two ivings, a bill, either partly or entirely horny, and 

 a body covered with feathers. They are distinguished 

 by these four characters from all other animals, and con- 

 stitute as it were an isolated class of beings, which does 

 not pass into any other, and which cannot, therefore, be 

 introduced without violence into the supposed chain or 

 gradation of natural bodies. 



Of these characters, one is peculiar to birds, viz. fea- 

 thers placed in regular order (in quincunx,) in the skin, 

 passing through a considerable quantity of fat, and thrown 

 oft" and again renewed at certain seasons of the year, 

 generally in autumn. Many, such as most water-fowl, 

 the ptarmigan, &c., moult twice in the year, in autumn 

 and in spring. In many species, the young birds, par- 

 ticularly before the first moulting, have different marks 

 or colours of the feathers, from those which the older 

 ones present. In many instances too, there are con- 

 siderable differences depending on the sex. The fea- 

 thers dirler from hair in this respect, that when once 

 cut or otherwise injured, they never, as far as is known, 

 are restored. 



The strongest feathers are in the pinions and tail: 

 the former are called Remiges, the latter Rectrices. 

 The pinion-feathers form, when the wing is expanded, 

 as it were, broad fans, by which the bird is enabled to 

 raise itself in the air_ and fly. Some few birds (aves 

 impennes), as the penguin, &c., have scarcely any pinion- 

 feathers, and are therefore unfit for flight. Some others 

 also, as the cassowary, diver, &c., have not any tail- 

 feathers. 



In their internal structure, birds are distinguished by 

 the remarkable receptacles for air dispersed through 

 their body, and of the utmost importance in assisting 

 their flight. They are mostly connected with the lungs, 

 sometimes, however, only with the throat, and can be 

 filled or emptied at pleasure. To these receptacles be- 

 long, in particular, large but delicate membranous cells, 

 situated partly in the abdomen, partly under the wings, 

 and elsewhere beneath the skin, and which can be filled 

 with air through the lungs. The cavities in some of 

 the bones, as of the shoulder, and in many cases even of 

 the head, contribute to the same objects, to which, also, 

 the enormous bills of the toucan and rhinoceros bird are 

 accessary. 



By these notable dispositions, birds are adapted for 

 flight, of which the rapidity, as well as the continuance 

 are alike remarkable. A few only, as the ostrich, the 

 cassowary, penguin, and other aves impennes, are incap- 

 able of flying. 



The abode of birds is nearly as various as that of 

 mammifera. Most live in trees: others in water; very 

 few wholly on the ground: and not a single bird undt-i 

 ground. The form of the foot in birds, as in mammifera, 

 is adapted to the difference of their abodes. 



Many birds change their residence at certain seasons ; 

 the greater number only in so far as that they remove a 

 few leagues into neighbouring districts, and speedily 

 return to their former situation: others, on the contrary. 



