32 FORM AND HABIT: THE BILL. 
corolla. In the Tooth-billed Hummer (Androdon) 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 (Dendrocolaptidw) 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, 
a slender, curved ones. 
Fie. 18.—Serrate bill of Merganser, a fish- Mergansers, Gannets, An- 
eating bird. (1/, natural size.) hingas, end. otlies arm 
that catch fish by pursuing them under water, have 
sharply serrate mandibles, which aid them in holding 
their slippery prey. 
Some shore birds (Limicole) use the bill as a probe, 
bo ee 
Fie. 19.—Probelike bill of Woodcock, showing extent to which upper mandi- 
ble can be moved, (2/s natural size.) 
when it may be six inches in length and straight, o 
curved downward. It has recently been learned that 
Fic. 20.—Recurved bill of Avocet. (2/, natural size.) 
several of these probing Snipe, notably the Woodcock, 
have the power of moving the end of the upper mandi- 
