* 



THE IBIS. 



ELEVENTH SERIES. 



Vol. I. No. 3. JULY 1919. 



XXI. — A preliminary Study of the Relation betiveen Geo- 

 yrapJiical Distribution and Migration with special reference 

 to the Paleearctic Region. By Lieut. -Col. R. Meinertz- 

 HAGEN, M.B.O.U. 



In studying the migration of birds we cannot confine 

 ourselves to a narrow view of dates of arrival, weather- 

 influence on migration, routes of migration, etc., but are 

 necessarily compelled to enquire into other oruithogical 

 problems which directly influence migration, such as the 

 questions of Moult, Sustenance on Migration, and others, 

 among which the problem of Geographical Distribution is 

 all-important. 



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 whiclv 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 on conjecture. The result is that many 

 distinguished authors did, and do still, hold opposite views 

 on similar migration-problems. 



SKtt. XI. VOL. 1. 2 E 



