THE SPRING MIGRATION OF BIRDS. 219 



record not only his own observations, but to urge 

 others, suitably placed, to go and do likewise. 



From a study of the various facts enumerated 

 in the present chapter, we may gather that Spring 

 Migration is undertaken from an irresistible im- 

 pulse to breed in a suitable temperature, so far 

 as concerns Species, and that Individuals, with an 

 inherent love for their birthplace and their home, 

 seek such conditions in certain localities each 

 season, returning unerringly to their old haunts, 

 by the old route, such being the only one they 

 know how to follow. Thus the pair of Willow 

 Wrens that nest in a sheltered nook in the distant 

 valley of the Yenesay return just as surely to their 

 old summer quarters so long as life exists within 

 them, and they are able to fly the long journey 

 from Africa ; just as surely as the pair of birds 

 that breed amongst the bilberries on the rocky 

 side of a Yorkshire coppice return to their summer 

 home, although the two localities are more than 

 3000 miles apart ! Yorkshire is the Mecca of 

 one pair — of many pairs — just as the Yenesay 

 or any other special haunt within the area of 

 the Willow Wrens' distribution becomes the Mecca 

 of all the rest ! Not only are the fly-iines to each 

 great centre different, but the necessities of the 

 journey are utterly dissimilar; and the Willow 

 Wrens breeding in Siberia could no more find 

 their way to English haunts, than could a Sun 

 Bird from South Africa find its way normally 

 to the Yorkshire hills. Migration in Spring may 



