148 THE STORY OF THE BIRDS. 
quiring paired toes, their habits have largely changed 
is shown by some of them, as road runners, taking to 
ground haunting—a condition where two toes in the 
rear is really in the way, since the best-formed birds 
for running either lose the rear toe or have it small 
and much elevated. The cuckoos’ remote ancestry 
runs by the way of the trees doubtless where paired 
toes were useful in clinging. 
We will dwell a little upon the interesting group 
of the woodpeckers and pass on more hurriedly, for 
we can not discuss all the peculiarities of these very 
remarkable birds. 
In the woodpeckers there is a wonderful series of 
specializations or modifications of the usual tools in 
keeping with an upright position on a tree trunk 
and the habit of digging into it. The outer toe is 
reversed alongside of the rear when at rest, but in use 
it is often set out horizontally, ready to pull the bird 
suddenly around the trunk. It seems as if its rever- 
sion might have come about through its use in this 
way. Evidently it is not now needful in limb clasp- 
ing, since few woodpeckers sit across small limbs; 
neither is it necessary in climbing as the woodpecker 
climbs—a well-known method, very unlike that of the 
parrots. The ordinary type of foot is as good if not 
better for simply ascending a trunk, as seen in nut- 
hatches, brown creepers, ete., which are more agile on 
an upright surface. Besides, the typical foot for 
simply clinging to rough upright surfaces has all the 
toes front, as seen in some swifts. Some wood- 
peckers even have the true rear (or inner back) toe 
