74 THE WOODPECKERS 



we should note that the flicker's bill is most like 

 the ordinary bill of perching birds, while the 

 drilling bill, as typified by the logcock's and 

 the hairy woodpecker's bills, is a more specialized 

 tool, limited to fewer uses, but more effective 

 within its limits. 



There is another detail of the woodpecker's 

 bills which casts light upon their habits. The 

 species that drill most have their nostrils closely 

 covered by little tufts of stiff feathers, scarcely 

 more than bristles, which turn forward over the 

 nostril. The density and the length of these 

 tufts agree very well with the kind of work the 

 woodpecker does ; for in the hairy and the downy, 

 which are continually drilling and raising a dust 

 in rotten wood, they are very thick and noticeable, 

 while in the red-head and the sapsucker they 

 show as scarcely more than a few loose bristles, 

 and in the flicker they barely cover the nostril. 

 This seems a plain provision to keep the dust 

 out of the bird's lungs ; and we might cite as 

 additional evidence the fact that the only other 

 birds of similar tree-pecking habits, the nut- 

 hatches and the chickadees, have their nostrils 

 protected in the same way. But we must al- 

 ways be cautious before drawing inferences of 

 this sort to see what may be said on the other 

 side. When we recollect that the crows and 



