The Migration of Birds 181 



ocean to the headwaters of some river, where the 

 eggs may be deposited in safety. The distance is 

 remarkable in the case of the quinnat salmon. It 

 ascends the Yukon to Caribou Crossing, two thou- 

 sand two hundred and fifty miles from the ocean! It 

 is well known that seals migrate regularly to certain 

 islands, known as breeding grounds, where the young 

 are born. These additional observations are helpful 

 in the study of migration of birds, and I believe they 

 strengthen the supposition that the existing conditions 

 are the results of changes that have been slowly pro- 

 gressing through past ages. 



Whatever may be the true theory, there is ever an 

 increasing charm about the study of migration, as 

 we note from year to year the comparative regularity 

 with which the birds come and go. It is not, as some 

 believe, a general helter-skelter movement among the 

 birds, but quite the opposite; it seems to be a regular 

 part of bird life, and they go about it in a business- 

 like manner, as though they knew there was some- 

 thing definite to be done. 



The extent of a bird's migration must necessarily 

 depend upon its food; a so-called resident bird, like 

 the crow, generally changes its food with the season. 

 Some birds depend upon fruit, others upon insects. 

 The insect-eating birds must migrate the farther of 



