INTRODUCTION, xix 
they utter loud, terrific, or piercing cries, in accordance with 
the gloomy rage and inquietude of their insatiable desires. 
Besides these grand divisions of the winged nations, there 
are others, which, in their habits and manners, might be com- 
pared to the amphibious animals, as they live chiefly on the 
water, and feed on its productions. To enable them to swim 
and dive in quest of their aquatic food, their toes are con- 
nected by broad membranes or webs, with which, like oars, 
they strike the water, and are impelled with force. In this way 
even the seas, lakes, and rivers, abounding with fish, insects, 
and seeds, swarm with birds of various kinds, which all obtain 
an abundant supply. There are other aquatic birds, frequent- 
ing marshes and the margins of lakes, rivers, and the sea, 
which seem to partake of an intermediate nature between the 
land and water tribes. Some of these feed on fishes and rep- 
tiles ; others, with long and sensible bills and extended necks, 
seek their food in wet and muddy marshes. These birds are 
not made for swimming ; but, familiar with water, they wade, 
and many follow the edge of the retiring waves of the sea, 
gleaning their insect prey at the recession of the tides: for 
this kind of life Nature has provided them with long legs, bare 
of feathers even above the knees; their toes, unconnected by 
webs, are only partially furnished with membranous appen- 
dages, just sufficient to support them on the soft and boggy 
grounds they frequent. To this tribe belong the Cranes, Snipes, 
Sandpipers, Woodcocks, and many others. 
In comparing the senses of animals in connection with their 
instinct, we find that of s¢gh¢ to be more extended, more acute, 
and more distinct in birds, in general, than in quadrupeds. I 
say ‘‘in general,” for there are some birds, such as the Owls, 
whose vision is less clear than that of quadrupeds; but this 
rather results from the extreme sensibility of the eye, which, 
though dazzled with the glare of full day, nicely distinguishes 
even small objects by the aid of twilight. In all birds the 
organ of sight is furnished with two membranes, — an external 
and internal, — additional to those which occur in the human 
subject. The former, membrana nictitans, or external mem- 
