The Migration of BirdsCoward, T. A. (Thomas Alfred)
Science
The Migration of Birds
Coward, T. A. (Thomas Alfred)
Birds -- Migration
Human beings, in varying degree, possess a sense of direction, and some
a wonderful power of finding their way in strange places; it is most
marked amongst those men we choose to call uncivilised, who, indeed,
live in closer touch with nature than those of us who depend so much on
compass, map, road, train and tram; we, as path-finders, are degenerate.
Middendorf marvelled at the powers of the Samoyeds, but when he
questioned them was met by blank surprise, and the cross-question--"How
does the little Arctic fox find its way aright on the great Tundra?"
In addition to this instinctive power, the bird has eyes and brain. We
can afford to put aside as purely speculative Middendorf's suggestion
that the bird is impelled or dragged by magnetic force, but we cannot
deny that it uses its eyes and that it has a wonderful memory; its
second journey will be easier than the first, for it will recognise
landmarks, just as the drake recognised something familiar when it
neared home. Sight, however, cannot be always necessary, for, at the
Kentish Knock Lightship, Mr Eagle Clarke noticed that birds flew so low
along the water that they could not possibly have seen their way.
It is purely speculative to say that the young bird which travels alone,
for it seems certain that many young do travel unguided on their first
journey, has an inherited memory of the actual route to be followed, but
that it has an hereditary sense of direction, or an hereditary impulse
to travel in a certain direction, is quite another matter. The sea, to
the young bird, may be a barrier; it may wander coastwise and be lost,
or, if this is the best way, find itself at the desired haven. If the
shortest and quickest way is across the ocean, the young bird may brave
the perils and succeed, or on this trackless waste it may wander till it
sinks to the waves and be added to the long list of failures.
Certain species summer in Greenland either in the same areas or in
areas comparatively near to one another; some of these travel in autumn
south-east, and winter in Europe or Africa, and others go south-west
into the States or South America. Most of these are distinctly eastern
or western forms, but occasionally American birds are met with in
Europe, and European in America. Probably at the start these stragglers
joined the wrong band, and travelled for company and unconsciously by
the wrong route. Birds drifted to leeward may find companions of quite
an alien tribe; others, wind-swept in this way, may travel alone to new
lands. A few pelagic South Pacific and South Atlantic petrels and other
birds have reached Europe from time to time, but theirs is an error of
too wide nomadic wandering. The wonder is not that these stragglers do
turn up, but that so few are noticed; probably the frequent mistakes
made by inexperienced or even experienced birds are speedily rectified
by nature; failure to find food or exhaustion spells death.
Public-domain text, read in full here on John Shaqi.
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