A great many of them must perish of hunger, or be reduced to
the necessity of feeding on the berries of the Viburnum and Juniper,
should they be overtaken by an extensive and enduring snow that cuts off
their journey of emigration.
The Woodpeckers and their allied species, though insectivorous, are not
thus affected by the winter. Gathering all their food, consisting of
larvae and insects, from the bark and wood of trees, the snow cannot
conceal it or place it beyond their reach. The quantity of this kind of
food is less than in summer, but the birds can obtain it with about
the same facility at all times, because other species of birds are
diminished, which in summer divide with them this spoil. Hence,
Woodpeckers, Creepers, and Tomtits do not migrate. They simply scatter
more widely over the country, instead of keeping in the woods, and thus
accommodate themselves to their more limited supplies of food. The
Swallow tribes, that catch their food in the air, are the first to
migrate, because the swarms of insects are vastly diminished by the
early frosts of autumn.
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