xxvi A HISTORY OF BIRDS 



our Swallows (for example) do not, as is supposed, on 

 reaching Africa disperse some to West Africa as far 

 south as the Gold Coast whilst others continue down 

 the East Coast to the Cape. But that, on the contrary, 

 our British birds, and those of France and Spain, go to 

 West Africa only. Those that are found along the 

 East Coast of that continent are birds which have been 

 bred in Eastern Europe. It is significant in this con- 

 nection that the Swallows of Northern Asia go south 

 to India and Burma, those of North America to South 

 Brazil. 



Our British migrants are held by Mr. Pycraft to be 

 so many " local " races of their species. Hence, he be- 

 lieves, has come about the extinction of many of our 

 " British " birds — Avocets, Spoonbills, Ospreys, Ruffs, 

 Bitterns, etc. As the parent stock is killed down, here 

 and abroad, no descendants are left to retyrn to the 

 old haunts, for the Avocets, Spoonbills, Storks, etc., 

 of the Continent are similarly so many " local " races, 

 having no "inherent knowledge" (if one may use the 

 term) of land outside their particular routes. That 

 migration was and is possible only to such species as 

 can obtain a livelihood outside their place of origin is 

 very justly asserted by our author. Hornbills, Toucans, 

 Birds of Paradise cannot migrate : outside their home- 

 range they would starve. Hence when the areas they 

 inhabit become over-stocked the surplus must perish. 

 Those birds more fortunate, because less specialised in 

 the matter of food, which find salvation in migration, 

 were driven back periodically to the land of their origin 

 by climatic conditions. Having, however, extended 

 their range and hence their breeding area, they returned 

 in greater numbers than those which departed. Hence 

 the land of origin was less able than before to support 



