TOOLS AND TASKS AMONG THE BIRDS. 149 
gone and the outer reversed in its place. It is not 
improbable that this true rear toe disappeared in 
these birds by disuse because of this constant up- 
right posture, and that the outer 1s there because of 
the dodging around habit. Later habits of occasional 
sitting across limbs have prevented the rear toes of 
others from going, and have given the outer toe also 
a limb-grasping use. In keeping also with this up- 
right posture the tail feathers are stiffened and spl- 
nous at the tip, to aid in supporting the body. 
The great specializations in favor of these birds, 
bearing directly on feeding habits, are the strong 
chisel- pointed straight beak and the long protruding, 
horn-tipped and barbed tongue, especially covered 
with slime. The beak is also much stiffened, and the 
tongue, besides being slimy to hold the grub, 1s so set 
that it may be darted far out with great force to pierce 
it. Our flickers feed on the ground partly, digging for 
ants and using the tongue for capture, and the near 
kin of the woodpeckers, the wrynecks, pick up all 
their living this way. If the woodpecker change his 
habit his beak may change with him, since the earth- 
digging flicker’s beak is not especially chisellike, but 
sharp pointed and curved down. 
Nature may compensate by special habits for 
many deficiencies of special tools. The imperfection 
of a tool may set up a new task or lighten one. To 
illustrate: Both woodpeckers and nuthatches nest in 
holes. The former opens his -by splintering all the 
wood into a solid tree away, but a nuthatch with 
his poor beak makes punctures in a circle, and 
