The Scottish Naturalist. 95 



performed ; how from the Scottish Border, they liave passed 

 over England to the coast of Sussex, thence sped their way 

 across the Channel to Spain, and onwards to the shores of the 

 Mediterranean ; where nothing daunted, they have braved the 

 elements, and finally reached the opposite shore ; no bark has 

 wafted them across the Straits, no compass guided them ; 

 instinct alone points out the route they are to pursue." 



The return of birds annually to the same spot is one ol the 

 numerous inexplicable facts which we see in migration, and 

 which would seem to be due also to other causes than the 

 mere fact of birth ; for Mr. Gray (Birds of West of Scotland, p. 

 92) mentions that in the belief that migratory songsters return 

 to their native haunts. Sir John Sinclair of Ulbster some years 

 ago attempted the introduction of nightingales into Caithness, 

 by obtaining numbers of nightingale's eggs from the neighbour- 

 hood of London, and placing them in robin's nests. Though 

 all were safely reared, and seen flying about in the vicinity of 

 their birthplace, they, in obedience to their migratory instincts, 

 quitted their northern home in September, and were never 

 afterwards heard of, and perhaps, he adds, they were right. 

 Might not this non-return be owing to a natural weakness ot 

 constitution in the nightingale, and its inability to endure the 

 cooler and more sunless counties of the north, for we know that 

 great numbers of summer visitants to these islands do not cross 

 the Tweed, not even crossing the Tyne, or rarely so, while on 

 the continent birds extend their migrations to latitudes higher 

 than the northern parts of Scotland. Why is this? Certainly 

 not for the want of suitable food, for of that there would be 

 abundance. 



As the northern parts of the Continent are much colder in 

 winter in comparison to Britain, driving birds many degrees 

 south of what they go in this country, so may it not be that 

 from a larger share of sun in summer, than in these sea girt 

 lands, they go farther north than they do with us; and this is 

 conspicuous in the Nightingale, the Wryneck, red-backed 

 Shrike, and many others, the former not going in these islands 

 higher than five miles north of York, "^ though found in Sweden 

 and Russia, t Does not this seem a proof that the apparent 

 susceptibility of heat and cold in different birds affects in a 

 great measure the extent of their migration. Some naturalists 



Yarrell, vol. I. 2nd. ed. , 304. f Gould's Birds of Great Britain, vol. II. 



