244 The Bird 
latter birds are fused together, to yield a firmer support 
for the muscles of the neck. 
Chimney Swifts and hummingbirds both feed upon 
insects and are rather closely related to each other, but 
here again the most decided difference is to be found in 
their bills. The broad, flattened mandibles of the swifts 
Fie. 1Ss.—Bill of Toucan; cut open to show its light, spongy structure. 
open wide, as the birds dash through the air, engulfing 
gnats and flies with wonderful skill; while the humming- 
birds, as we all know, probe the deepest calyxes. Could 
two bills more unlike be imagined? In very young hum- 
mingbirds the bill is short and broad, very like the swift 
type, and later its long and slender shape is acquired 
