32 



FOEM AND HABIT: THE BILL. 



corolla. In tlae Tooth-billed Hummer {And/rodon) both 

 mandibles are finely serrate at the end, the upper one 

 being also hooked, and the bird feeds on insects which it 

 captures on the surface of leaves and other places. 



Among the Woodhewers (Dendrocola/ptidm) of South 

 America there is fully as much variability, which reflects 



equally variable feeding 

 habits. Some species have 

 short, stout, straight bills, 

 others exceedingly long, 

 slender, curved ones. 

 Mergansers, Gannets, An- 

 hingas, and other birds 

 that catch fish by pursuing them under water, have 

 sharply serrate mandibles, which aid them in holding 

 their slippery prey. 



Some shore birds {Limioolm) use the bill as a probe. 



Fig. 18.— Serrate bill of Merganser, a fish- 

 eating bird. ('/! natural size.) 



Fio. 19. — Probelike bill of ■Woodoook, showing extent to which upper mandi- 

 ble can be moved. (Ya natural size.) 



when it may be six inches in length and straight, or 

 curved downward. It has recently been learned that 



Fio. 20. — Kecurved bill of Avocet. (^3 natural size.) 



several of these probing Snipe, notably the Woodcock, 

 have the power of moving the end of the upper mandi- 



