THE HUMMING BIRDS. 165 



catchers, distinctly heard when darting through the 

 air, at once indicates the nature of its sustenance. 

 For this reason they often frequent the borders of 

 streams ; and are seen skimming over the surface of 

 ponds of water, where a minute insect life is most 

 abundant. The bills also of many species are pro- 

 vided with seratures, to enable them more certainly 

 to secure their prey. The corollas of many large 

 tubular flowers are infested by microscopic insects, 

 which undoubtedly attract the birds, as well as the 

 sweet nectar contained in the cup below; and to ob- 

 tain which they are furnished with a tongue formed 

 like that of the Woodpeckers, divided into two tubes 

 which run throughout its entire length, and is capa- 

 ble of being protruded to a considerable distance 

 from the point of the beak, thus serving the purpose 

 of a pump to draw up the honey from the deep re- 

 cesses of the flower, while it is also used to collect 

 the insects from the corolla. 



In most species of Humming Birds there is a wide 

 difference noticeable in the plumage of the males and 

 the females, the latter being rarely if ever clothed 

 with the rich metallic hues of the former. In a few 

 instances where the coloring of both sexes is plain, 

 no difference is apparent. The young birds do not 

 generally attain their full livery until the second or 

 third year; they make their first appearance in the 

 sombre garb of the female, which gradually changes 

 with each successive moulting until maturity. 



The structure of the scale-like feathers which 



