176' THE STORY OF BIRD LIFE. 



complete coincidence to a complete separation of 

 the breeding and the subsistence areas ; when 

 natural liistory of a sufficient number of species 

 is thoroughly worked out, we may find every link 

 between species which never leave a restricted 

 area in which they breed and live the whole year 

 round, to those other cases in which the two areas 

 are absolutely separated." 



We have one striking instance of the relations 

 between migration and food in the passenger 

 pigeon, Edopistes migratorius. Concerning this 

 Dr Brewer writes, "The wild pigeon appears to 

 be almost entirely influenced in its migration by 

 the abundance of its food, excepting in those 

 parts of the country in which it has not been 

 known to remain during the winter. Even in 

 these movements it is largely influenced by con- 

 siderations of food. . . . They are capable of 

 propelling themselves in long continued flights, 

 and are known to move with an almost incredible 

 rapidity, passing over a great extent of country 

 in a very short time. It is quite a common and 

 well ascertained fact that pigeons are captured in 

 the state of New York with their crops still filled 

 with the undigested grains of rice that must have 

 been taken in the distant fields of Georgia in 

 South Carolina, apparently proving that they 

 must have passed over the intervening space 

 within a very few hours. Audubon estimates 

 the rapidity of their flight as at at least a mile a 

 minute. . . . Mr Audubon relates that in 1813 

 ... in crossing the barrens near Hardensburg, 

 he observed these birds flying to the south-west 

 in greater numbers than he had ever known 



