OF THE BILL OF BIRDS. 159 
the larvee of insects, as the Rook is known to do 
habitually ; and, accordingly, the plumage at the 
base of the bill of this individual, and the bristly 
feathers which cover its nostrils, are very con- 
spicuous, not. having sustained the slightest in- 
jury. 
The last instance of this anomalous structure of 
the bill which has fallen under my observation 
occurred in a specimen of the Red-headed Wood- 
pecker (Picus erythrocephalus, Linn.) contained in 
a collection of birds’ skins lately brought from the 
United States of North America. In this indivi 
dual the mandibles, though pretty much elongated, 
are but slightly curved, the upper one, as in the 
preceding cases (Mr. Wood’s Rook alone excepted, 
in which the direction is reversed), crossing the lower 
one on the right side. A bill so constructed must 
have proved exceedingly inconvenient to a bird of this 
species. 
I might now proceed to speculate upon the 
circumstances which contributed to produce this 
phenomenon; but as my acquaintance with the 
history of the birds in which I have seen it exhi- 
bited is so imperfect, that any thing I could ad- 
vance concerning them would be little more than 
conjectural, I shall not enter into the inquiry. 
