THE GLACIAL RANGE CONTRACTION, ETC. 159 



not breeding on any other part of the Pacific shores 

 of the American continent, because such areas could 

 only be reached by a flight south in spring. It 

 explains why the Little Bunting breeds in Siberia 

 within the same parallels of latitude as the British 

 Islands, and only in North Russia in Europe ; why 

 the Eastern Nightingale breeds from Asia Minor to 

 South Sweden, yet is unknown in Western Europe ; 

 why the Red-backed Shrike breeds throughout the 

 whole of Europe south of lat. 64", with the sole ex- 

 ception of the Iberian Peninsula ; why the Nightingale, 

 the Reed Warbler, and other birds are absent from the 

 south-west of England ; why Ticrdus alicice, Junca 

 hyeiiialis, yEgialztts semipalmatiis, and Tryngites rufes- 

 cens cross over into North-eastern Siberia to breed 

 yet return to their range bases in America to winter ; 

 why Phylloscopiis borealis and Erithacus sitecica, after 

 spending the summer in Alaska, return to winter exclu- 

 sively in the Old World ; together with scores of other 

 anomalies of distribution which space alone forbids me 

 to enumerate. I appeal to naturalists interested in that 

 fascinating branch of ornithology which embraces 

 Geographical Distribution and Migration to apply this 

 Law ; for I am confident that it will lead to important 

 results, and explain many anomalies ; perhaps even 

 enable us to remodel on a more satisfactory and natural 

 basis the various regions into which the world has been 

 divided by zoologists. 



We began with the vast change of climate that marked 

 the closing era of the Pleistocene Period, and endeav- 

 oured to trace its effects upon the avifauna in particular 

 of Western Europe ; we have sketched out the probable 



