igiQ-J Geoyraphical Distribution and Migration. 391 



liaving a very local breeding-area, such as the Passemger- 

 Pigeon, Esquimaux Curlew, and Labrador Duck, or to 

 species which, having a large range, are unable to resist 

 slaughter at all seasons. Systematic egg-stealing under the 

 cloak of science, but which in reality is the travesty of 

 science, is also responsible for such contraction of range, as 

 in the case of so many birds which have within the last 

 century ceased to be included among British breeding-species. 



Indirect human agency has increased the breeding- 

 range of certain species, though only in a minor degree. 

 The re-afforestation of land and artificial sheets of water 

 have, no doubt, helped in this manner, though in most cases 

 it has been a case of re-establishment. The carrying of 

 migratory birds on ships comes under this heading. 



In like manner has interference with terrain^ such as the 

 draining of the Fens, contracted the breeding-range of 

 birds. The introduction of a destructive element has had 

 similar efiect, as in the case of the arrival of the pig in 

 Mauritius which completed the sad fate of the Dodo, or the 

 great mortality among sea-birds from the torpedoing of a 

 tank-steamer and the resultant film of oil spread over vast 

 areas of sea. 



From these examples it will readily be seen how closely 

 related are migration, distribution, and differentiation among 

 birds. Without the framework of distribution the study of 

 migration can only lead to theory. Each separate species 

 or subspecies must be studied, if possible throughout its 

 range, and then we shall arrive at facts from which the 

 whole narrative of migration can be read. No two species 

 which have a similar geographical distribution are known 

 to have similar migratory habits. We even get, among birds 

 of tiie same species, vast differences in migratory habit, 

 hence the great importance of detailed study. 



The task is gigantic, and though no one human life can 

 hope to complete the Mork, a combined eflbrt by all field- 

 naturalists and collectors, with the very great assistance 

 supplied by the various organizations in Britain, America, 



