IN THE SHETLANDS 41 
as it sweeps by, just gives a flick with the back of 
them, which the other revenges or parries with a blow 
of the wing. 
The tern, however, having a straight and sharply 
pointed bill, adapted for pecking, and nothing else, 
can use it in this manner when flying also, though in 
other respects it delivers its attack in exactly the same 
manner as the gull does, allowing for the difference in 
bulk and aerial grace and mastery, between the two 
birds. Here, as it appears to me, we see structure 
affecting habit. As a rule, I think, it is rather the 
other way, for it is wonderful to how many uses, other 
than the primary one for the performance of which it 
has been specially adapted, almost any part of an 
animal’s anatomy may be put. And indeed, if we 
look at it in another way, this truth is as strikingly 
illustrated by what we have just been considering as 
by almost anything, for the webbed foot of a gull or 
any swimming bird is extremely unadapted for fighting, 
and yet we here see it thus employed. But it is owing 
to the structure of the beak, in my opinion, that this 
has come about. That is the bird’s real weapon, which 
I am convinced it would always use if it could or if it 
dared. Not even in their rough-and-tumbles, where 
they close and roll over and over together, have I seen 
gulls fight with their feet, upon the ground. 
I had not gone far, after this episode with the terns, 
when I was pecked at, twice again, by another one, 
under similar circumstances. Each time, I believe, 
the sharp point of the beak went through the slight 
