January 
little practice to bring the glass to bear instantly 
on the precise point ; and if not done at once, 
the bird is likely to be so disobliging as to 
change its position, and you will run the risk 
of losing it altogether. It is advisable to gain 
facility in this matter by fixing the eye on some 
remote but distinct object, like the end of a 
branch, and learning to cover it instantly with 
a glass. The opportunities of seeing specimens 
are too valuable to be wasted in such practice. 
The absence of foliage in winter makes a 
vast difference in the ease of discovering birds, 
and of following their motions as they go from 
tree to tree. A delicate aspen-leaf can hide a 
warbler, and any of the larger song-birds can 
be lost behind a leaf of maple or of oak, while 
the plumage often blends confusingly with the 
foliage. In the case of the sparrows, which are 
peculiarly ground-birds, it has been ingeni- 
ously suggested that their prevailing neutral 
colors prove them to be the ‘‘survival of the 
fittest’? to escape the sharp eyes of their vari- 
ous enemies, all the brighter-colored species (if 
there ever were any) having been gradually 
exterminated. 
In the construction of their nests, too, it is 
often evident that birds feel the necessity of 
21 
