GLACIAL EPOCHS AND POLAR CLIMATES. 45 



such conditions having prevailed in past ages; 

 there is much evidence that the centre of dispersal 

 of many groups of birds is Antarctic. 



Now it is a remarkable and suggestive fact that 

 among the Charadriid/E the species breeding in 

 what we may well describe as the North Polar 

 Basin have the longest migrations of any known 

 birds. The following half-dozen species are among 

 the most Arctic of birds. First we may instance 

 the Sanderling {Calidris areiiaria), breeding in 

 the North Polar Basin, and extending its winter 

 migrations southwards to the Malay Archipelago, 

 the Cape Colony, and Patagonia ; second, the 

 Turnstone {Strepsilas interpres), whose breeding 

 range is circumpolar, and extends into the Arctic 

 regions, whilst its winter range touches pretty well 

 every extensive coast-line south of the Tropic of 

 Cancer; third, the Curlew Sandpiper {Triiiga 

 subarquata), which breeds on the highest North 

 Polar land, and extends its winter flights as far as- 

 Austraha; fourth, the Knot [Tringa canutus), 

 which breeds within the narrow compass of the 

 North Polar Basin, and in winter wanders ta 

 Australia, New Zealand, Cape Colony, and Brazil ; 

 fifth, Bonaparte's Sandpiper {Tringa honaparti)^ 

 which breeds in Arctic America, and in winter 

 reaches Patagonia and the Falkland Islands ; sixth,, 

 the Red-throated Stint (Tringa riificollis), breeding 

 in North-eastern Siberia, but how far north is not 

 precisely known, and in winter extending its 

 southern flight to Australia. Two of these species- 



