RECENT EMIGRATION 183 



or that follow them north again in spring. So far as the 

 Summer Visitors that are extending their range in our 

 islands are concerned, the movement is slowly increasing 

 the length of their journey, and slightly varying the 

 route that they follow ; with the Resident species it is in 

 many cases compelling the adoption of local migratory 

 habits. It may be remarked that this local migration is 

 much more marked and general on the Continent than it 

 is in our island area, where the climate is so much milder ; 

 more species perhaps partake in it, and the flights are 

 longer and more dominant, and rise to a much greater 

 degree of importance. Thus we find many species 

 absolutely migratory in continental areas, no individuals 

 remaining through the winter that are sedentary or 

 nearly so with us, in the sense of never being absent 

 from our islands all the winter through. In the above 

 table I have indicated the species that are migratory in 

 the northern portion of their British area, but we need 

 not stay to enter into greater details of their movements. 

 Some of these, I may remark, have already been de- 

 scribed in the Migration of Bij-ds, and to that volume I 

 would refer the reader who may be sufficiently interested 

 in the subject to desire fuller information. 



In order to render the present subject fairly complete 

 it is now necessary to devote a little space to the con- 

 sideration of a very different set of facts from those 

 which we have been studying ; to make a brief allusion 

 to those species which have passed more or less 

 completely from our avifauna, and whose absence has 

 been very largely caused by those very improvements 

 that have been so advantageous to other species. Our 

 drainage and reclamation of waste lands, our game pre- 



