98 FRIENDS WORTH KNOWING. 



ence of altitude accomplishing the same climatic results as 

 a change in latitude. 



We can see various causes of these migrations, some of 



ONLY A OAT-BIED." 



which have already been suggested, but the chief cause 

 seems to be the necessity of their accustomed food. "We 

 find that those birds which make the longest and most com- 

 plete migrations are insect and honey -eaters; while the 

 graminivorous and omnivorous birds, and such, like the tit- 

 mouse and nut-hatch, as subsist on the young of insects to 

 be found under the bark of trees, go but a short distance to 

 escape inclement weather, or do not migrate at all. Sports- 



