42 
_the crops of a single species of wildduck, the Scoter, or Black 
Duck, concluded that a flock numbering 1,000 of these 
birds would destroy per year sixty tons of cockles. He found 
twelve or fifteen cockles in eachcrop. Assuming that they 
eat about thirty a day, which would be a very moderate cal- 
culation, and allowing for their absence during the breeding 
season, this would make some seven million cockles, equal to 
about sixty tons. The ducks obtain them by following the 
tide in, and shovelling the cockles out of the loose, sloppy 
sand. I have followed the writer’s observations, and con- 
sider he is rather under than over the mark. However, I 
have seen this one species of duck in such quantities that 
1,000 might easily have been taken away and not made 
much difference. 
Another bird which exists in thousands in Morecambe 
Bay, the oyster catcher, is responsible for an enormous 
destruction of cockles, and they form a large portion of 
the food of sea gulls of many varieties. These are part of 
the destructive forces at work when the tideis out. When 
it isin, countless myriads of plaice and other fish are feed- 
ing on them. Any such caught on the banks will be found 
to be gorged with them, and from their multitude it would 
be well within the limits to say that the crop that man 
takes is a small quantity of the whole; and as man is in- 
cessantly taking the plaice and other destroyers, it almost 
follows that to allow a fair proportion of cockles to grow to 
