PERCHING BIRDS. 141 
billed birds. These have, as you see in Fig. 117, the head 
of a Shrike or Butcher-bird, a notch or tooth near the 
extremity of the upper bill or mandible. This is like the 
a 
Fig. 117.—Head of Shrike. 
notch seen in the upper mandible of birds of prey (§ 214); 
and accordingly we find that those which have this notch 
well developed are really birds of prey, living on small 
birds and reptiles, as well as the insects and worms which 
are the common food of all this group. The Shrikes, 
Thrushes, and Warblers are examples of this division. 
3. Tenuirostres (tenuis, thin, slender, and rostrum), slen- 
der-billed birds. These slender bills are specially fitted 
either for sucking up vegetable juices or for picking up 
insects. The Humming-birds are the typical birds of 
this group. 4. Fisszrostres ( fissura, a slit, and rostrum), 
gaping -billed birds. The bills or mandibles are very 
broad and flat toward their base, and the slit or fissure 
between them. is carried far back under the eye. This 
arrangement gives them, when the mandibles are moved 
apart, a very broad and widely-opened mouth, as seen in 
the Goatsucker, Fig.118 (p.142). This, you see, is strong- 
ly in contrast with Fig.116. The purpose of this conform- 
ation is to allow these birds to take insects on the wing, 
