40 THE BEAN GOOSE. 
by their black and orange bills; but, as already mentioned, the 
particular species figured is, I think, arvensis and not the true 
segetum, which is smaller, besides having much more black on 
the bill. It may be that, as Bechstein says, the older and more 
mature birds lose a good deal of the black on the bill, and so 
become arvensis; but this is not Naumann’s view, and Naumann, 
who studied every species carefully in life, is rarely in error in 
such matters. 
