16 Forest Birds. 
There is still another peculiarity in the anatomy 
of the Woodpecker. When climbing a tree it must 
necessarily keep its body very close to the trunk, or 
the strain on the legs would be too great, and to 
enable the bird to accomplish this, a specially-formed 
breast-bone has been provided. ; 
On comparing the breast-bone of the Green Wood- 
pecker with that of another bird of abcut the same 
size, viz., the stock dove (Columba sxnas), we 
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Breast-bone of Green Woodpecker. 
From nature. Natural size. 
notice at once a difference in the size and shape, 
which is truly wonderful. The breast-bone of the 
Green Woodpecker has a very low keel (Fig. 3), and 
this dwarfing of the keel enables the bird to cling 
closely to the tree. The stock dove on the contrary has 
acorrespondingly high keel to the breast-bone (Fig. 4), 
and the reason for this is soon found, for the stock 
dove is indued with great powers of flight, and 
since the pectoral muscles, which move the wings, are 
