WILD LIFE OF ORCHARD AND FIELD 



All birds migrate more or less — even such, like 

 the crow and song-sparrow, as stay with us through 

 the year; for we probably do not see the same 

 individuals both winter and summer. Even trop- 

 ical birds move a little way from the equator, and 

 back again with the season; and in mountain- 

 ous regions most of the birds, and many small 

 quadrupeds, have a vertical migration only, de- 

 scending to the valleys in winter, and reascending 

 to the summits in summer — difference of altitude 

 accomplishing the same climatic results as a 

 change in latitude. 



We can see various causes of these migrations, 

 some of which have already been suggested, but 

 one potent cause seems to be the necessity for an 

 accustomed food. We find that those birds which 

 make the longest and most complete migrations 

 are insect and honey eaters; while the grami- 

 nivorous and omnivorous birds, and such, like the 

 titmouse and nuthatch, as subsist on the young 

 of insects to be found about the bark of trees, go 

 but a short distance to escape inclement weather, 

 or do not migrate at all. Sportsmen recognize 

 the fact that the snipe and woodcock have returned, 

 not because the rigorous winter days are wholly 

 passed, but because the frost is sufficiently out 



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