Page:The Zoologist, 3rd series, vol 2 (1878).djvu/246

224 Curlew down to the Dunlin, which abound in this locality. Next to man, however, I am inclined to think that the Scoter, or Black Duck, is the worst enemy with which the cockle has to contend. A short time ago two of these birds were sent to me which had been shot in the neighbourhood of Grange, at the head of Morecambe Bay. I had the curiosity to examine the contents of their gizzards, and was surprised to find that they were both crammed with the shells of cockles, to the exclusion, apparently, of any other kind of food. Several of the shells were still entire, and measured half an inch in diameter. The rest, some of which had evidently been of much larger dimensions, had been broken up by the grinding process they had undergone. There could not have been less than the remains of a dozen cockles in each of the specimens I examined, and, supposing that a Scoter would eat from twenty to thirty in a day, a flock containing a thousand of these birds would devour in the course of a season (allowing due time for their absence at their breeding stations) not less than seven million cockles, amounting in weight to at least sixty tons. And yet a flock of a thousand Scoters does not represent a tithe of what may be seen in the bay at any time during the winter months. The mode in which these ducks procure their food is peculiar, and until I found it out I was at a loss to understand why they might so frequently be 6een swimming in the shallow water at a distance of from fifty to a few hundred yards from the water's edge. As the rising tide covers the banks, the sand, for the depth of an inch or two, is gradually stirred up until it becomes a semi-liquid mass. The cockles, which, unlike mussels, are not attached to any foreign substance, lie at about this depth below the surface, and the ducks, swimming up on the advancing flood find no difficulty in diving or reaching down and extracting them from their sandy bed. The same tidal action tends, doubtless, to disperse the spat given off by the parent cockle during the breeding season, and explains how they are able to move (whether of their own free will or not I am unable to say) from place to place. No doubt, too, it is in this way that the shell-fish which live beneath the sand obtain their food—a fact which finds support in the evidence of one of the witnesses, who alluded to the mortality produced among the cockles by severe frosts. Thus far the case against the birds appears as black as possible; but, on the other hand, we are met by the unanswerable argument that thirty years ago the birds were ten times as numerous as they are at present; and yet, according to the evidence of the opponents of sea-birds, the shell-fish were also far more plentiful than is now the case. These are facts which it is hard to reconcile, and we must be content to suppose that in those days there was room enough for the birds, the cockles, and their human enemies to live without the weaker species being