284 THE MIGRATIOy OF BRITISH BIRDS 



majority of cases must inevitably end in failure. Some 

 ornithologists arc disposed to explain ditticult problems 

 of geographical dispersal by similar irruptic movements, 

 but in the face of such damning proof to the contrary 

 such an explanation should never be invoked, unless 

 supported by absolute demonstration. Once more let 

 me assert most emphatically that the dispersal of birds, 

 nay of all organisms, is governed by Law, not by 

 chance, that it is not fortuitous but the result of 

 design. 



Once more I repeat, Birds do not increase their range 

 in winter. It /s this all-iinpovtant fact tJiat keeps species 

 to their iionnal areas of dispersal. If winter conditions 

 led to extension of range or emigration, then species 

 would wander fortuitously far and wide, and such a 

 thing as geographical limits would be almost unknown 

 — especially in temperate and boreal latitudes, where 

 the food supply is ever a fluctuating one. The more 

 I study the question, the more I am convinced that 

 Dispersal or Range Expansion is solely the result of 

 increase, and that the spasmodic, totally abnormal, wan- 

 derings of species in quest of sustenance during winter 

 or the non-breeding season, can never lead to emigration 

 or permanent extension of area. 



