AN ORNITHOLOGICAL LECTURE. 97 



there are many exceptions to this rule, for with not a few 

 birds the males and females travel together; and with some, 

 old and fully plurnaged males are the last to arrive. 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 tropical 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, 



THE HUMMING- BIRD'S NEST. 



have a vertical migration only, descending to the valleys in 

 winter, and reascending to the summits in summer differ- 



7 



