330 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1950 



wrens do, namely, take to the seashore. And I am pretty sure that 

 if the house sparrow ever reached Keykjavik, the capital of Iceland, 

 it would flourish and multiply. 



The greatest puzzle, perhaps, is that posed by the Lapland bunting, 

 which breeds in Greenland and north of the Arctic Circle in Norway, 

 but not in Iceland, although it seems to traverse the island regularly 



on passage 



That for strong fliers the climate is the only obstacle is shown 

 by the fact that since the beginning of this century the list of breed- 

 ing species has been increased by nearly 10 percent, undoubtedly 

 owing to the amelioration of the climate — a fact to which I shall return. 



Again, swallows come to Iceland every summer (we saw some in 

 the Westmann Islands) as do willow warblers, but neither species has 

 yet been found breeding. 



It seems that many species are all the time sending out scouts, 

 so to speak, into areas where breeding is impossible but on the chance 

 that one day they can establish themselves permanently. This seems 

 a wasteful method, but natural selection always involves wastage. 

 The most striking example is the painted lady butterfly {Vanessa 

 cardui), which cannot reproduce itself regularly through the winter 

 north of southern France, but in most years sends out vast numbers 

 to Britain and other countries. The one we ourselves saw, by Lake 

 Myvatn, was nearly 1,500 miles outside its permanent range ! 



Another interesting feature of broad geographical distribution is 

 this — that Iceland is at the same time the westernmost outpost of a 

 number of Old World bird species and the easternmost of some (but 

 fewer) New World ones. Actually Lake Myvatn is the area of maxi- 

 mum overlap between the bird faunas of what zoologists call the Pale- 

 arctic and the Nearctic regions, northern Eurasia and North America 

 respectively. 



Thus Iceland is the western limit of breeding range for such Old 

 World species as whooper swan, greylag goose, snipe, golden plover, 

 whimbrel, redwing, white wagtail (and indeed the entire wagtail 

 genus) ; but it is the eastern limit for the otherwise New World species, 

 great northern diver, Barrow's goldeneye, and harlequin duck. The 

 ducks, by the way, well illustrate the complexities of geographical 

 distribution — Iceland shows us not only several Old World species at 

 their western limit, like wigeon, teal, common scoter, and tufted 

 duck, but also a number of circumpolar or Holarctic species such as 

 mallard, pintail, gadwall, and shoveler. 



It is noticeable that all the New World species which breed in 

 Iceland are hardy enough to inhabit parts of Greenland also. If the 

 Labrador Current did not cool the east coast of Greenland and northern 

 Canada so much below the temperature they ought to enjoy by virtue 

 of their latitude, and the Gulf Stream did not warm Iceland and 



