226 Birds Every Child Should Know 
timorous beastie suspects there is a foe abroad. 
As owls live upon mice, mostly, it is important 
they should be helped to catch them with some 
device that beats our traps. If mice should 
change their nocturnal habits, the owhs whole 
scheme of existence would be upset, and the 
hawks would get the quarry that they now 
enjoy: mice, rats, moles, bats, frogs and the 
larger insects. You see the farmer has in- 
valuable d?ay and night allies in these birds of 
prey which take turns in protecting his fields 
from rodents, one patrol working while the 
other sleeps. On the whole, owls are the more 
valuable to him. They usually continue their 
good work all through the winter after the 
hawks have gone South. Can you think of any 
other birds that work for him at night? 
Not only can owls fluff out their loose, mottled 
plumage, but they can draw it in so close as to 
change their shape and size in an instant, so 
that they look like quite different birds, or 
rather not like birds at all, but stumps of trees. 
Altering their outlines, changing their shape 
and size at will, is one of these queer birds* 
peculiarities. Their eyes, set in the centre of 
feathered discs, do not revolve in their sockets, 
but are so fixed that they look only straight 
ahead, which is why an owl must turn his head 
every time he wishes to glance to the right or 
left. Another peculiarity is the owls’ method 
