dless variety in the avi-faunal life of the Rockies.
Some species breed far above timber-line in the thickets that invade the
open valleys, or clamber far up the steep mountain sides. Others ascend
still higher, building their nests on the bald summits of the loftiest
peaks at an altitude of fourteen thousand feet and more, living all
summer long in an atmosphere that is as rare as it is refreshing and
pure. Among these alpine dwellers may be mentioned the brown-capped
leucostictes, which shall be accorded the attention they deserve in
another chapter. Then, there are species which have representatives both
on the plains and far up in the mountain parks and valleys, such as the
western robin, the western meadow-lark, and the mountain bluebird.

In this wonderful country there is to be observed every style of
migratory habit. A twofold migrating current must be noticed. While
there is a movement up and down the mountain heights, there is at the
same time a movement north and south, making the migratory system a
perfect network of lines of travel. Some species summer in the
mountains and winter on the plains; others summer in the mountains pass
down to the plains in the autumn, then wing their way farther south into
New Mexico, Mexico, Central America, and even South America, where they
spend the winter, reversing this order on their return to the north in
the spring; others simply pass through this region in their vernal and
autumnal pilgrimages, stopping for a short time, but spending neither
the summer nor the winter in this latitude; still others come down from
the remote north on the approach of autumn, and winter in this State,
either on the plains or in the sheltering ravines and forests of the
mountains, and then return to the north in the spring; and, lastly,
there are species that remain here all the year round, some of them in
the mountains, others on the plains, and others again in both
localities. A number of hardy birds--genuine feathered Norsemen--brave
the arctic winters of the upper mountain regions, fairly revelling in
the swirling snow-storms, and it must be a terrific gale indeed that
will drive them down from their favorite habitats toward the plains.

Does the avi-fauna of the Rocky Mountain district differ widely from
that of the Eastern States? The reply must be made in the affirmative.
Therefore the first work of the bird-student from the East will be that
of a tyro--the identification of species.