66 THE MIGRATIONS OF BIRDS 



60O5 and finally, in some instances, to 1,000 miles, all 

 in more or less the same direction. The percentage 

 of returns and the short periods required for the 

 journey in case of some of the longer flights are 

 truly marvellous. 



Two factors seem to enter, first, some peculiar 

 attribute that for lack of a better name we may 

 term a sense of direction, which drives the flier on 

 the proper course, and, second, a memory of place 

 that enables the pigeon to recognize landmarks in 

 the vicinity of its home when it has arrived. 



It must be admitted that, though recognition of 

 landmarks that guide the bird on its journey are of 

 assistance in travelling air-lanes crossed on previous 

 occasions, this cannot wholly explain the ability that 

 enables a bird successfully to drive across unfamihar 

 areas a hundred, or several hundred, miles in extent. 

 In most instances there can be no dependence upon 

 sight recognition of distant landmarks, as many ex- 

 periments, in fact the main ones that have been re- 

 ported in this country, have been carried out in 

 regions of low relief, where landmarks would not be 

 visible beyond 25 to 50 miles even from a point a 

 thousand feet or more above the earth. Further- 

 more, experiment has shown that in good strains of 

 homing pigeons it is possible for a fair proportion of 

 young birds to return to their homes from a distance 

 of 15 to 20 miles, when they have not had the ad- 



