98 ZOOLOGY. 
necessary for striking the air is provided by feathers different from those 
of other parts of the body, called wing-feathers or quills. In many birds, 
similar feathers appear in the tail, which is used for governing flight. 
The mechanical adjustments by which the wings are fitted for use as 
organs of flight, are very beautiful. Birds do not rise or sustain them- 
selves in the air because of any special lightness of their bodies, which are 
in fact much heavier than the air, but by the action of their wings upon 
it, and its resistance to them. The legs of birds consist of parts corre- 
sponding to those of the legs of man, but the thigh is short, and concealed 
within the body, the apparent thigh corresponding to the human leg, and 
the shank, which serves the bird as a leg, to a part of the foot—Some 
birds are very useful to man, as affording, in their flesh and their 
eggs, valuable articles of food; but the number really of import- 
ance in this respect is very small in comparison with the multitude 
of species, and the useful kinds belong mostly to two orders, Rasores 
and Natatores, to be presently noticed. 
We can only indicate in a few sentences the orders of birds. The 
order Acciprtres,| Rapaces,? or Raptores,? contains birds of prey, the 
food of which is the flesh of animals, chiefly other birds and quad- 
rupeds. They are characterised by great strength of claws and bill. 
The upper mandible of the bill is hooked and sharp. The claws 
also are generally hooked and sharp, and the feet formed for seizing 
prey. The wing is generally large and pointed. This order is divided 
into two groups, Diurnal and Nocturnal, the first containing eagles, 
falcons, hawks, vultures, &c.; and the latter consisting entirely of owls. 
—The order Insessores* is a very large one, consisting of birds which 
have weak, slender feet, not adapted for seizing prey, but generally for 
perching on trees, Like the Birds of Prey, and most of the birds of other 
orders, they have four toes, three directed forward, and one backward. 
The bill is weak and little curved. The wings are of moderate size, and 
generally rounded. Some of the Insessores feed chiefly on insects, some 
on seeds or fruits, some indifferently both on animal and vegetable food. 
To this order belong crows, thrushes, linnets, larks, sparrows, humming- 
birds, birds of paradise, &e.—The order Scansores® consists of birds very 
similar to Insessores, but having two toes behind and two before, so that 
their feet are peculiarly adapted for grasping and climbing. Parrots afford 
perhaps the best example of this order. Woodpeckers also belong to it. 
—The Rasores,® or Gallinaceous Birds,’ have a bill of moderate size, short 
wings, a heavy body, weak toes, and short, stout claws. In general, 
1 Latin, plural of accipiter, a hawk. : 5 Latin, ‘climbers,’ from scando, scansum, 
2 Latin rapa, rapacious. to climb. 
3 Latin, plural of raptor, a seizer or 6 Latin, ‘scrapers,’ from rado, rasum, to 
plunderer. scrape. 
4 Latin, ‘sitters,’ from sedeo, sessum, to sit. 7 From Latin gallus, a cock. 
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