ADAPTATION FOR THE INDIVIDUAL 103 
Most of our birds meet this difficulty by changing 
their base of operations. When the north grows cold 
these creatures fly to the south. Some of their mi- 
grations cover enormous stretches of country. Our 
bobolink, so well known and loved by all watchers 
of spring migrations, passes twice a year between the 
latitude of New York and Rio Janeiro. One of our 
most careful students of bird migration says that the 
Golden Plover makes, twice each year, the long jour- 
ney from the Arctic shores of North America to the 
plains of La Plata. 
Different fur-covered animals have specialized to 
meet the winter by any one of three different methods. 
They may brave it out, hunting for their food as best 
they can all winter long. Such a course is pursued by 
the rabbit. Again like the squirrel, they may store 
large quantities of food during the summer, and on 
this provender they may subsist during winter, re- 
maining for most of the time near their hiding-places, 
which, however, they may frequently leave upon 
warm days. A third method is less common, but very 
interesting. The groundhog or woodchuck is the 
best-known example of the group. It remains asleep, 
or, as it is technically known, dormant, during the 
winter. This stupor is more profound than ordinary 
sleep, and from it these animals awaken with diff- 
culty. It is needless to remark that the groundhog’s 
