The Birds’ Calendar 
ent for its validity upon the particular geo- 
graphical location of the observer, this third 
method is conditioned by some very interesting 
facts of science, viz., the laws governing their 
appearance and disappearance, as they come 
and go periodically. 
As the object of these pages is not merely to 
give a succinct account of the several species 
one is likely to find in the course of a year’s 
observation, but to make the whole scheme of 
bird-life more intelligible by treating briefly 
of the more important phenomena observable 
among them collectively, it is essential to speak 
of that curious and extremely interesting phase 
of their history—bird-migration ; and no time 
is more opportune for this explanation than 
February—‘‘so full of frost, of storm, and 
cloudiness,’’ so unfavorable for outdoor study, 
and immediately preceding the first of the 
year’s migrations. 
Even the most unobservant person is prob- 
ably aware that the robins and bluebirds ar- 
rive in the spring, and go away some time in 
the fall; but he is not so likely to know that, 
on the other hand, there are many species, un- 
known to him by name or appearance, like 
kinglets, nuthatches, crossbills, shrikes, pine 
48 
