Ixxxvi 



MAPS OF DISPERSAL. 



greatest penetration at the lowest levels, and also to further illus- 

 trate what effect upon migrants (real migrants) similar circumstances 

 of weather might, or do, produce. 



The map of the Little Auk illustrates both the inroad of the 

 species by certain routes, and in some degree also the bulking of 

 migrants in Forth, as compared with their arrivals and inland 

 dispersal in Tay ; and also the comparative power of these two 

 catchment basins for receiving migrants; and it may perhaps sug- 

 gest the comparative importance of the Bell Rock and Isle of May 

 positions, which I speak of in the Introduction. The complete 

 account of the irruption of Little Auks is given very fully and 

 completely in Mr. W. Eagle Clarke's papers referred to in the 

 text, p. 348. 



The other two examples of the mapping of the breeding, dispersal, 

 and migration of species will be found under the species respectively, 

 and may be consulted generally under various other species besides 

 those they were specially designed to illustrate} 



^ In the maps of the dispersal of these three selected species the uorth-east 

 limit or boundary of Tay is shown running out at Stonehaven. But, as I have 

 explained, I have removed that boundary to a line more closely following the 

 county march, and running out at Girdleness. (See general map of the area.) 



