170 BIRDS THROUGH AN OPERA-GLASS. 



hooked at the end for holding insects ; but per- 

 haps the most extreme cases of adaptation are to 

 be found in those of the kingfisher, humming- 

 bird, crossbill, and night-hawk. In the night- 

 hawk and whippoorwill the enormous fish-trap of 



the kingfisher is exchanged for almost no bill 

 at all, merely a hook and eye for a wide gaping 

 mouth. 



The night-hawk and whippoorwill are the most 

 nearly related of the four birds we have from the 

 order of "goatsuckers, swifts, etc." They are 

 both brown-mottled birds, and are similar in build 

 and general habit. The swifts resemble the night- 

 hawks in having narrow clear cut wings, small 

 bills, and big mouths, but in habit they are almost 



