INTRODUCTION. 
11 
hand, and as an impermeable oar on the other, when situated in the 
wing, and required to catch and retain the impulse of the air. In 
the birds which do not fly, and inhabit warm climates, the feathers 
are few and thin, and their lateral webs are usually separate, as in the 
Ostrich, Cassowary, Emu, and extinct Dodo. In some cases 
feathers seem to pass into -the hairs, which ordinarily clothe the 
quadrupeds, as in the Cassowary, and others ; and the base of the 
bill in many birds is usually surrounded with these capillary plumes. 
The greater number of birds cast their feathers annually, and 
appear to suffer much more from it than the quadrupeds do from a 
similar change. The best fed fowl ceases at this time to lay. The 
season of moulting is generally the end of summer or autumn, and 
their feathers are not completely restored till the spring. The male 
sometimes undergoes, as we have already remarked, an additional 
moult towards the close of summer ; and among many of the waders 
and web-footed tribes, as Sandpipers, Plovers, and Gulls, both sexes 
experience a moult twice in the year, so that their summer and 
winter livery appears wholly different. 
The stratagems and contrivances instinctively employed by birds for 
their support and protection, are peculiarly remarkable ; in this way 
those which are weak are enabled to elude the pursuit of the strong 
and rapacious. Some are even screened from the attacks of their 
enemies by an arrangement of colors assimilated to the places which 
they most frequent for subsistence and repose : thus the Wryneck 
is scarcely to be distinguished from the tree on which it seeks its 
food ; or the Snipe from the soft and springy ground which it fre- 
quents. The Great Plover finds its chief security in stony places, 
to which its colors are so nicely adapted, that the most exact observer 
may be deceived. The same resort is taken advantage of by the 
Night-Hawk, Partridge, Plover, and the American Quail, the young 
brood of which squat on the ground, instinctively conscious of being 
nearly invisible, from their close resemblance to the broken ground 
on which they lie, and trust to this natural concealment. The same 
kind of deceptive and protecting artifice is often employed by birds 
to conceal, or render the external appearance of their nests ambigu- 
ous. Thus the European Wren forms its nest externally of hay, if 
against a hay-rick ; covered with lichens, if the tree chosen is so 
clad ; or made of green moss, when the decayed trunk in which it 
is built, is thus covered; and then, wholly closing it above, leaves 
only a concealed entry in the side. Our Humming-bird, by external 
