70 THE BIOLOGY OF THE SEASONS 



Eastern to Western Scotland, as with many starlings ; or 

 from hill to valley, or from moorland to shore. We have 

 been able to prove that a thrush may migrate from 

 Aberdeenshire to Lisbon, and a black-headed gull to Bor- 

 deaux, but these are only short journeys probably parts 

 of a longer prospective journey in the cases mentioned. 

 It has been proved that storks from Germany may migrate 

 to Natal, and of some other birds it may be said with 

 confidence that they fly half across the earth. The Curlew 

 Sandpiper and the Knot breed so far north that their eggs 

 have rarely been found, and yet the birds have been seen 

 in New Zealand in winter ! " They must have performed 

 a southern flight equal to nearly half the circumference of 

 the globe." 



Even more striking is the very interesting fact reported 

 by Dr. W. S. Bruce of the Scotia, that the Arctic Tern was 

 observed " wintering " in the Antarctic summer in 74 i' 

 S. lat. It is well known as a breeding bird on our own 

 coasts to 82 N. lat. We have here, so far as is known, 

 " the greatest latitudinal range of any vertebrate animal." 



(2) In the Northern Hemisphere most birds migrate 

 between a colder area which love enlivens, where they 

 breed, and a warmer area where hunger is avoided, where 

 they winter. It is a cardinal fact, to which there are few 

 exceptions, that birds breed in the coldest part of their 

 migratory range. 



In emphasising the fact that most birds in the Northern 

 Hemisphere are migratory, and that in a perfectly definite 

 way, we must, however, make it plain that the range of the 

 migration may be very limited, and that many kinds of 

 birds are only partial migrants, some individuals leaving 

 the country and others staying. In many cases the 

 migration is greater than it seems, because the place of 

 individuals that have slipped southwards in Autumn may 



