A PRELIMINARY STUDY OF THE RELATION BETWEEN 
GEOGRAPHICAL DISTRIBUTION AND MIGRATION 
WITH SPECIAL REFERENCE TO THE PALAEARCTIC 
REGION + 
By Col. R. MEInERTZHAGEN, M. B. O. U. 
In studying the migration of birds we can not confine ourselves to 
a narrow view of dates of arrival, weather influence on migration, 
routes of migration, etc., but are necessarily compelled to inquire 
into other ornithological problems which directly influence migration, 
such as the questions of molt, sustenance on migration, and others, 
among which the problem of geographical distribution is all im- 
portant. 
Until quite recently the study of migration was built on a sea of 
theories, sometimes based on no evidence and at other times based 
on insufficient data. Many authors had generalized on purely local 
facts and attempted to apply to all birds a principle which was only 
manifest in a single species at some isolated lighthouse or on some 
island observatory. The interpretation of facts was often attempted 
before those facts were themselves accurately known, and opinion 
was in many cases based not on knowledge, but cn conjecture. The 
result is that many distinguished authors did, and do still, hold op- 
posite views on similar migration problems. 
By applying existing theories to migration in general, it was 
found that they were usually only applicable to a particular species 
at one particular spot, and it became apparent that until a fairly 
comprehensive grasp could be got of the migration of each species 
throughout its range we should not progress to any great degree. 
The rules governing the migration of a species in Great Britain 
need not necessarily apply to that same species when passing from 
its summer quarters in other parts of the world to, say, India or 
Egypt. Each species contains many communities, and even very 
small local colonies, whose summer and winter homes and routes of 
migration are governed by laws which are almost individualistic. 
Not only each species and subspecies, but every small colony or family 
of birds presents on occasions a separate problem, the solution of 
which may differ in accordance with the many varied laws governing 
+1 Reprinted by permission from The Ibis for July, 1919, 
339 
