e birds travel sometimes in family
groups and sometimes in large flocks, moving southward little by
little, according to season and food-supply, some journeying as far as
Mexico, others lingering through the middle and southern states. The
Bluebirds that live in our orchards in summer are very unlikely to be
those that we see in the same place in winter days. Next to the
breeding impulse, the migrating instinct seems to be the strongest
factor of bird life. When the life of the home is over, Nature
whispers, "To wing, up and on!" So a few of the Bluebirds who have
nested in Massachusetts may be those who linger in New Jersey, while
those whose breeding haunts were in Nova Scotia, drift downward to fill
their places in Massachusetts. But the great mass of even those birds
we call winter residents go to the more southern parts of their range
every winter, those who do not being but a handful in comparison.

"What does this great downward journey of autumn mean?" you ask. What
is the necessity for migration among a class of birds that are able to
find food in fully half of the annual range? Why do birds seek extremes
for nesting sites? This is a question about which the wise men have
many theories, but they are still groping. One theory is that once the
whole country had a more even climate and that many species of birds
lived all the year in places that are now unsuitable for a permanent
residence. Therefore, the home instinct being so strong, though they
were driven from their nesting sites by scarcity of food and stress of
weather, their instinct led them back as soon as the return of spring
made it possible.

Thus the hereditary love of the place where they were given life may
underlie the great subject of migration in general and that of the
Bluebird's home in particular.

[Sidenote: The Bluebird at Home.]

Before more than the first notes of spring song have sounded in the
distance, Bluebirds are to be seen by twos and threes about the edge of
old orchards along open roads, where the skirting trees have crumbled
or decaying knot-holes have left tempting nooks for the tree-trunk
birds, with whom the Bluebird may be classed. For, though he takes
kindly to a bird-box, or a convenient hole in a fencepost, telegraph
pole or outbuilding, a tree hole must have been his first home and
consequently he has a strong feeling in its favor.

As with many other species of migrant birds, the male is the first to
arrive; and he