4 HUMMING-BIRDS. 



(Docimastes), where it is used in probing to the base of the long 

 tubular flowers from which it derives its food. 



The tongue is long, composed of two cylindrical united tubes, 

 and bifid at the tip. It is capable of being protruded for some 

 distance, the tongue-bones with their muscles being prolonged 

 backwards and upwards over the back of the skull as in the 



Skull of Humming-bird witb. tongue, a, tougue, bifid at the end ; b, muscle 

 retracting the tongue ; c, muscle protruding the tongue. 



Woodpeckers. The wings have ten primaries, and are, as a 

 rule, narrow and pointed, apparently most unsuited for a sus- 

 tained flight ; but they are set in motion by enormously developed 

 muscles which render the body of these tiny birds much heavier 

 than one would expect. The sternum, which gives attachment 



Front and side views of the breast-bone of a Humming-bird. 



to these muscles, has a very deep keel and a rounded posterior 

 margin without indentation or fissure. The tail is wonderfully 

 varied in shape throughout the family, and in many instances 

 highly ornamented ; it consists of ten feathers and no more. 

 The tarsi and feet are particularly small and feeble, and quite 

 unfit for progression on the ground. These birds, however, 

 seldom or never alight on the earth, but prefer to settle on a 

 bare dead limb of a tree or some other projection. The eggs 

 are oval and white, and always two in number. The nest is a 



