INTRODUCTION. XXVil 
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 Sand- 
pipers, 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 remark- 
able ; 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 frequents. 
The Great Plover finds its chief security in stony places, to 
which its colors are so nicely adapted that the miost 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, instinc- 
tively 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 appearance of their nests ambiguous. Thus the 
European Wren forms its nest externally of hay, if against 
a hayrick; 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 patches of lichen, gives her nest the appear- 
ance of a moss-grown knot. A similar artifice is employed by 
our Yellow-breasted Flycatcher, or Vireo, and others. The 
