58 THE BIOLOGY OF THE SEA-SHORE 



associations and communities prey upon one another will be 

 treated in a later chapter, and it only remains here to stress 

 the fact that, in addition to the struggle that is maintained 

 among themselves, they are subject not only to the pre- 

 datory visits of creatures belonging to the deeper waters 

 during high tide, but also to incursions by land forms during 

 the periods of low water. 



A good instance is given by Stafford (1901), who states 

 regarding My a arenaria that, although buried, and hence 

 escaping the open direct struggle to which the mussels are 

 subject, they are nevertheless preyed upon by a considerable 

 number of animals. They may be washed out by storms 

 and cast on shore or left to die in the sun, or ravaged by 

 gulls, cormorants, crows, etc. In places along the New 

 England coast, pigs systematically visit, root up and eat the 

 clams. In Greenland they are sought after by walrus, 

 Arctic fox, and birds. Their siphons are often found in 

 the stomachs of fish such as flounder and sculpin, which also 

 eat the young, while cod will eat them if they get the chance. 

 Starfish are one of their greatest dangers, and the whelk 

 bores holes in the shell. Crabs are likewise enemies. Man 

 is a great enemy, leaving many exposed, to die or fall a prey 

 to other creatures. M'lntosh (1896) found that the ova 

 of the Lumpsucker, Cyclopterus lumpus, were eaten by rooks 

 and other birds, while at the same time (April) cod were 

 found to be distended with the same food. The same 

 authority records that another common bird, the sparrow, 

 has been noticed to be destructive to the young flounders 

 in the harbour. *' At ebb-tide in May this bird watches by 

 the side of the tiny pools in the mud and seizes on a young 

 flounder whose prominent glistening eyes (minute though 

 they be) are sufl^cient to betray it, though its almost trans- 

 parent body is immersed in the mud. It then lays it on 

 one side, and watches for another, and so on until it has a 

 fair mouthful to carry to its young " (M'Intosh, 1888). 



Of the destructive action of sea-gulls, one instance must 

 suffice. Scott (1915) writes that on visiting the Bardsea 

 cockle beds in Morecambe Bay, his attention was drawn to 



