a 
NATURAI, HISTORY. 
exposure to the air, the bird is furnished with a gland situ- 
ated on the rump of the animal, containing a proper 
quantity of oil, which it presses out with its beak, and 
occasionally anoints its feathers. In water, fowl this oil is 
so plentiful that it even imparts a degree of rancidity to 
the flesh, and we see that their coat of feathers is rendered 
by it completely water-proof. 
The wings of birds are remarkably strong. The flap of 
a swan’s wing would break a man’s leg, and a similar blow 
from an eagle has been known to lay a man dead in an 
instant. 
The sense of seeing in birds is remarkably acute, and 
though they have no external ear, but only two small ori- 
fices or ear-holes, yet they do not appear to be deficient in 
hearing. The scent of some species is exquisitely delicate. 
In decoys, where ducks are caught, the men who attend 
them generally keep a piece of turf lighted, on which they 
breathe, lest the fowl should smell them and fly away. 
The voice ol birds is much louder in proportion to their 
size than that of other animals, for in fact, the bellowing 
of an ox is not louder than the scream of a peacock. 
The legs, the wings, the bones, and every part of the 
body, are much lighter, firmer, and more compact in birds 
than in other creatures. Their lungs are extended all 
over the cavity of their body. 
Carnivorous birds, like carnivorous quadrupeds, have 
but one stomach, and that well calculated for digestion. 
Those that feed on grain have, in addition to the crop or 
stomach, where their food is moistened or swelled, a giz- 
zard, which is a very hard muscle, almost cartilaginous or 
gristly, and which they commonly fill with small stones, 
where the food is afterwards ground, in order to Us com- 
plete digestion. Birds are subject to few diseases. 
Birds of the same species do not always make their 
nests of the same materials, though in general there is a 
uniformity; the red-breast in some parts of England 
makes its nest with oak leaves where those leaves are 
plenty, in other parts it makes it with moss and hair. 
Where the eggs are numerous, it is necessary to make the 
nest warm % thus the wren, which is a small animal, and 
able to cover but a small compass, and yet lays many eggs, 
makes her nest remarkably warm ; on the contrary the 
plover, the eagle, the crow, &c. which lay but two or 
three, are not equally solicitous in this respect. 
There are some birds which are called birds of passage, 
