2 72 Birds Every Child Should Know 
birds and their exquisite little cousins, the 
terns or sea-swallows, had been slaughtered. 
Then some people said the massacre must stop 
and happily the law now says so too. Paid keep- 
ers patrol some of the islands where gulls and 
terns nest, which is the reason why you may see 
ashy-brown young gulls in almost every flock. 
When they mature, a deep-pearl mantle covers 
their backs and wings, and their breasts, heads 
and tails become snowy white. Their colour- 
ing now suggests fogs and white-capped waves. 
Why protect birds that are not fit for food 
and that kill no mice nor insects in the farmer’s 
fields ? is often asked. A wise man once said 
'‘the beautiful is as useful as the useful,” but 
the picturesque gulls are not preserved merely 
to enliven marine pictures and to please the eye 
of travellers. They fill the valuable office of 
scavengers of the sea. Lobsters and crabs, 
among many other creatures under the ocean, 
gulls, terns and petrels, among many creatures 
over it, do for the water what the turkey buz- 
zard does for the land — rid it of enormous 
quantities of refuse. When one watches hun- 
dreds of gulls following the garbage scows out 
of New York harbour, or sailing in the wake of an 
ocean liner a thousand miles or more away 
from land, to pick up the refuse thrown over- 
board from the ship’s kitchen, one realises the 
excellence of Dame Nature’s housecleaning. 
