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SS — Ul he 
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SESSION 1899-1900. 
IlL—THE MIGRATION OF BIRDS. 
By Mr W. EAGLE CLARKE. 
(Read Nov. 22, 1899.) 
_ Mr CiarkE remarked, at the beginning of his paper, that the 
British Isles were eminently suited to observe bird migration 
in all its aspects, the majority of British birds being purely 
migratory, while the geographical position of the islands and 
_ the climatic changes experienced also afforded the naturalist 
opportunity to study those species which made this country 
a temporary home in their passage to other climes.  Illus- 
trations were then thrown on the screen of the different 
species met with in Great Britain, and the migrational routes 
that were followed—it being observed by Mr Clarke that 
migration, instead of being exceptional, was almost universal. 
_ Explaining why birds went northwards in spring and south- 
_ wards in autumn, he asked what would become of the birds 
if they attempted to winter in the north? The answer was 
_ that they would certainly perish, not from cold, as was popu- 
larly supposed, but from want of food, migratory birds being 
largely dependent on special food, chiefly insects. Some doubt 
_ might be felt whether, in the return movement in spring, 
_ scarcity of food was again the cause. It might be urged that, 
while fitted for a winter resort, the tropical regions were not 
suited as a nursery. On the other hand, summer in the 
temperate northern region afforded an abundant food-supply, 
VOL. IV. F 
