IN THE SHETLANDS 129 
pretty rose tapestry of the mouth-chamber must be 
plain to each or either, and the more so that they are 
U1S-A-UI5. 
In all these four birds, therefore, we have a nuptial 
habit of distending the jaws, side by side with a bril- 
liant or pleasing coloration of the region which, by 
such action, is exhibited. Moreover, in the case of 
one of them, more particularly—viz. the fulmar 
petrel—this distension may be unaccompanied with 
any note, though it always is with the odd gestures 
and lackadaisical expression which I have tried to 
describe. In: other words, the beak is sometimes 
opened as a part of the bird’s nuptial actions, and not 
merely with a view to the production of sound. That 
originally this alone would have been the motive of its 
being so can hardly, I suppose, be doubted, but may it 
not be possible that the eye has gradually come to 
share in a pleasure which was, at first, communicated 
through the ear alone, and that a process of selection, 
founded, perhaps, on some initial freshness of colour- 
ing, has in time produced a special kind of adornment ? 
If this were so, we might expect that some of the 
birds so adorned would have the habit of opening the 
billin this manner without uttering any note at all, or, 
at least, that they would very frequently do so. Such 
an instance we have in the shag, that smaller and more 
adorned variety of the cormorant, which is much more 
common on our northern coasts than the so-called 
common one. One of the most ordinary nuptial 
actions of these birds is to throw the head into the air, 
K 
