EARLY IDEAS OF MIGRATION
The evolution of the study and knowledge of migration is an interesting
subject, dealt with more or less completely by several writers. In a
manual it is impossible to treat it fully. That the Greek poets--Homer
and Anacreon for instance, and the writers of Jeremiah and Job, knew
something about the regular movements of birds is evident, nor is it
surprising that in lands like Greece, Egypt and Palestine the passage of
birds should be noted and directly connected in the popular mind with
the seasonal changes.
In a measure similar observations and conclusions may be traced in
the history or traditions of most peoples, but in a northern detached
area, such as the British Islands, there is a marked tendency to
overlook passage and note only arrival and departure, mostly of summer
birds. Early observers noticed the swallow and cuckoo when they had
actually come, and missed them when they had gone, but they failed to
grasp whence they came or whither they went. Interchange of ideas with
inhabitants of other lands was limited, and few early travellers were
philosophers, at any rate so far as migration was concerned. In Germany,
however, the Emperor Frederic II. realised in the thirteenth century
many truths concerning migration (27), but in Britain uncertainty or
myth held sway until the end of the eighteenth century. Herr Herman,
reviewing the variation in thought, says--"But as in other fields, this
period is followed by a time of decadence, a natural consequence of
departing from immediate experience."
British, and many Continental observers too, saw when birds had come
and in autumn that they had gone. Early swallows and martins were
always met with near water, and were watched dropping to roost in the
reed beds, as they always do in autumn before departure. Next morning
none was visible. Certainly then they had vanished to hibernate in the
water. The discovery of masses of torpid swallows, dead or dying, by
no means an unknown thing when birds are overtaken by sudden falls in
temperature in autumn or by a severe setback in the spring, was to these
puzzled men confirmation of their theory of hibernation. Other details
of the many stories of swallow hibernation are due to exaggeration or
to misconception. In the second half of the eighteenth century a fierce
discussion waged for and against hibernation, and many, including
Geoffroy St Hilaire and Montagu, sat on the fence, admitting that it
might be possible with some species and probably was with swallows.
Later some Americans produced "evidence" in favour of avian hibernation,
and even Mr Charles Dixon, in his earlier book at any rate, did not
think it impossible (25). The only argument in favour of hibernation
is that it is a habit resorted to by other vertebrates to escape the
consequence of exposure to severe temperatures. The arguments against it
are that not a single instance of avian hibernation will stand the light
of reason and investigation, and that birds are provided with the means
of escaping from the cold zone and certainly use these means. There
are flightless birds, but they all live in climates in which they can
exist at all seasons. As Seebohm puts it--"The hibernation of birds is a
theory, the evidence in support of which has completely broken down. The
migration of birds is a fact, as completely authenticated as the fact of
their existence."
Dr Derham's "Physico-Theology" appeared in 1737 (24), and contained
some sound reasoning about migration, though he was a little puzzled
with the many hibernation stories. In 1780 an anonymous pamphlet--"A
Discourse on the Emigration of British Birds," flouted the theory of
winter sleep in no measured terms (33). This pamphlet was, at first,
attributed to George Edwards, and the 1811 edition has his name on the
title, but Mr A. C. Smith shows that the real writer was a comparatively
unknown man, John Legg. Legg must be looked upon as one of our first
real students of migration. It is Legg who refers to a pamphlet which
appeared in 1740 in which it was seriously argued that swallows migrated
annually to the moon.
All this time, from 1736 onwards, the family of Marsham in Norfolk, had
been quietly recording observations on the arrival of migrants, each
generation continuing the work. The accumulated results have been used,
and will be used again, in studying the science of "ornithophænology."
A myth, founded on mistaken observation as well as upon mere speculation
was, and to some extent still is, that the larger migrants assist the
passage of the weaker ones. How else, is still asked, can weak-winged
species cross the sea? It was an old legend when J. G. Gmelin heard it
from the Tartars in 1740; each crane they told him took a corncrake on
its back. There are men who know the corncrake well, who believe to-day
that the bird must skulk unseen through the winter, for they assert it
is quite incapable of lengthy flight. It is useless to argue with them;
the only answer is that it not only can, but regularly does perform a
long double journey; its range extending from northern Europe to South
Africa. In 1911 I handled a water-rail, a bird with short rounded
wings like those of the corncrake, which had struck the lantern of a
lighthouse with great violence. Its smashed head was nearly severed from
its body.
Herr Otto Herman's "Recensio critica automatica" (31) supplies much
information about the literature on bird migration, and the strange
divergence of opinion on nearly every point. It is carried up to the
beginning of the twentieth century, but much of the valuable work done
in America is altogether neglected.
A short bibliography is given at the end of the present volume,
including the more important works on the subject and a few of the
papers in periodical publications referred to in this manual.
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