16 FIELD KEY TO THE LAND BIRDS. 
WOOD PECKERS. — Picidae. 
BILL. — Strong and straight. 
Cae Drees: = Not feathered. 
—— Tors. — Four, two in front and two 
behind, or three, two in 
front and one behind. 
Nails strongly curved for 
climbing. 
Koop. — Insects, particularly wood- 
boring insects in the trunks of trees. 
For the purpose of catching these insects Wood- 
peckers are provided with a long, string-like tongue 
which has a barbed hook at the point. They insert 
this tongue into the holes bored by the insects, and 
pull out. their prey. When the tongue is not long 
enough they hammer and chisel tioles with thei 
strong bills, and thus reach the insect. They build 
