IN THE SHETLANDS 7 
able that crouching in a bird should have come before 
flying than after it, or, at least, that it should have 
been resorted to by certain species, on account of 
their flight having become weak. It is conceivable 
that some birds may have alternately lost and re- 
acquired the power of flight many times in their 
genealogical history. But where have the majority 
of the young gulls gone? That they have left the 
island seems evident, for, were it otherwise, they 
would either be all about the heather, or fill the air 
more numerously than do the mature birds, when 
they cluster above me in my walks. In the air, how- 
ever, none are to be seen, though, as by far the 
greater number must now be full-fledged, it is there 
that they ought to be, with the rest. On the ground 
there are, as I say, a few that seem to have been later 
hatched, and are not yet matriculated in flight. Their 
proportion, however, is not more than one to a hun- 
dred of the grown gulls, whereas since every pair 
of these rears three young, it should be as three to 
two. Gilbert White speaks of that general law in 
accordance with which young birds are driven away 
by their parents, when they are no longer dependent 
upon the latter’s attention, but can feed and look after 
themselves ; but with social birds this law of expul- 
sion is apt to merge in a larger one, that, namely, 
which is expressed in the old adage that “birds of a 
feather flock together.” We often see this illustrated 
in the case of the sexes, and after watching kittiwakes 
at the close of the breeding-season, I can have no 
