Geologically considered, the migration of birds had its origin in the
beginning of the Post-Tertiary period of our globe’s history. Prior to
the Glacial Epoch there was no migratory instinct among the feathered
tribes of the earth’s fauna for the simple reason that there was no
necessity for such a change of habitat.
Thus the annual recurrence of this phenomenon has been going on not
since the creation, as many suppose, but for units of ages whose lapse
can be reckoned only by millenniums of calendar years. It is not the
time and place here to discuss the means by which this length of time
can be even approximately determined, but there are certain inferences
and conclusions which are well endorsed by scientific research.
For our present purpose it is quite sufficient to say that the Glacial
Epoch wholly changed the climatic relations of the polar and middle
latitude regions of our globe. From the semitropical conditions which
once perennially existed there, these regions have since and for ages
been subject to the intense cold which now periodically prevails within
those limits.
There is a growing conviction among geologists that the intense cold of
the Glacial Epoch was caused by a change in the eccentricity of the
earth’s orbit. If this be true, then the “Great Winter” of astronomers
was reigning in all its severity 210,000 years ago.
The wild goose, his near relatives, the brant and swan, and other
aquatic feathered races, made their appearance on the fifth day of
creation. “And God said, Let the waters bring forth abundantly the
moving creature that hath life, and fowl that may fly above the earth in
the open firmament of heaven.”
Now this fifth day of creation very nearly corresponds to the Triassic
and Jurassic periods of Mesozoic Time in Geology.
Although “every winged fowl after his kind” is included in the bird
category of this creative act, it has been thought, and for good
reasons, that the more highly organized birds other than the aquatic
tribes, did not make their appearance till the sixth day of the Mosaic
account, which would be exactly represented by the Tertiary Period of
Cenozoic Time. According to this view, then, the wild goose is an older
denizen of our world than the smaller birds of passage which make their
home on the land only.
But Geology fills up many niches and supplies many details left blank in
the first chapter of Genesis. It is now one of the firmly established
tenets among geologists that between the Mesozoic and Cenozoic times
there came a tremendous disturbance in the earth’s crust.
In his “Story of the Earth,” Dr. J. Dorman Steele says, “The Mesozoic
time, like the Palaeozoic, was closed by mighty upheavals. The
conditions of life were changed. All the Mesozoic types disappeared;
hardly any species survived the shock.” A few individuals did survive,
however, and among them was our venerable friend, the wild goose.
Having now finished the prefatory portion of our story, the reader will
be better able to understand what may follow.
There is something wonderful, a conception, indeed, which smacks little
short of the sublime in contemplating the protracted journeyings of the
larger aquatic birds of passage. Especially is this true of the American
wild goose, the brant and the swan. The brant is the wild goose of Great
Britain and continental Europe; a much smaller bird than his American
relative; and its migrations are of comparatively short range.
The European domesticated swan, remains, of course, the year round in
the country of his adoption.
Not so, however, with the American goose and swan. Both the former,
Anseres hyperboreas, and the latter, Cygnus buccinator, rear their young
in the Arctic regions and spend the succeeding winter with their
offspring in the Gulf States and Central America.
Think of these magnificent birds, those on the Pacific coast flying from
the shores of the Arctic ocean in northern Alaska and British America,
crossing the Rocky Mountains, and, after a journey of four or five
thousand miles, complacently settling down in Texas, Mexico, Yucutan, or
Nicaragua, as the experienced leaders may determine. Then turn to those
on the Atlantic side of the continent and watch them as they leave the
Baffin’s Bay country, cross the great lakes and the Appalachian mountain
system to make a short winter sojourn among the everglades of southern
Florida.
In the tactics of these great birds while performing their immense
journeys there is something remarkable even to the casual observer. More
than two thousand years ago it was recorded by a student of natural
history that, “Olores iter facientes colla imponunt praecedentibus;
fessos duces ad terga recipiunt.”
“Swans performing a journey rest their necks upon those preceding; and
the leaders receive the weary ones upon their backs.”
And this significant remark has often been confirmed by modern
observation.
Owing to the fact that they are more sparsely distributed, that they fly
much higher and in smaller numbers than wild geese, the swans are
comparatively seldom seen during their migratory flights save in the
fastnesses of mountainous districts or at the extreme points of arrival
and departure. Hence we see why so little is known concerning the
details of their aerial movements.
On the contrary, the semi-annual passage of wild geese is not only a
folk-lore phenomenon, but a familiar spectacle to the residents of
cities and towns as well as those who spend their days in the rural
districts. Now, there is more military precision in the alignment of a
large flock of wild geese than the most careful observer ever dreamed of
or science investigated.
Here in the fastnesses of our Rocky Mountains there are many
exceptionally good opportunities for watching the marvelous evolutions
of these birds.
While their flight may be a mile high or more when spanning a level
scope of country, as in the prairie districts, they barely clear the
more elevated peaks while crossing lofty mountain ranges. Hence it will
be seen that an observer on either slope is much nearer the passing
birds than an inhabitant of the lower levels or plains.
The well known acute angled form assumed by wild geese in their annual
journeys is not a mere fortuitous conceit on the part of the birds, but
a true pattern of that diagram formulated by the anserine leaders of
long agone prehistoric ages; brave old heroes that piloted their snowy
hosts over the storm-lashed wastes of northern latitudes while frost and
fire and glacier and drift were so radically changing the topography of
our globe.
It can be shown that this particular form of alignment in the flight of
geese is just as essential to the convenience and vital interests of the
birds as the hexagonal form of honeycomb cells is to the bees that
construct and fill them with honey. Nay, it is also true that no other
form of alignment in flight could fulfill the conditions required; but
we cannot here explain the principles involved in the interesting
discussion.