Indirect Benefits, : 151 



their own food among the dews, yield a most fattening nou- 

 rishment to the sheep." {Hist, of Cornwall, p. 286.) 



Among birds the Mollusca have many enemies. Several of 

 the duck and gull tribes, as you might anticipate, derive at 

 least a portion of their subsistence from them. The pied 

 oyster-catcher receives its name from the circumstance of 

 feeding on oysters and limpets (Patella vulgaris), and its bill 

 is so well adapted to the purpose of forcing asunder the valves 

 of the one, and of raising the other from the rock, that " the 

 Author of Nature," as Derham says, " seems to have framed 

 it purely for that use." Several kinds of crows likewise 

 prey upon shellfish, and the manner in which they force the 

 strong hold of their victims is very remarkable. A friend of 

 Dr. Darwin's saw above a hundred crows, on the northern 

 coast of Ireland, at once, preying upon muscles. Each crow 

 took a muscle up in the air twenty or forty yards high, and let 

 it fall on the stones, and thus broke the shell. Many autho- 

 rities might be adduced in corrobation of this statement. In 

 Southern Africa so many of the Testacea are consumed by 

 these and other birds, as to have given rise to an opinion that 

 the marine shells found buried in the distant plains, or in 

 the sides of the mountains, have been carried there by their 

 agency, and not, as is generally supposed, by eruptions of the 

 ,sea. Mr. Barrow, who is of this opinion, teJls us, in con- 

 firmation of it, that " there is scarcely a sheltered cavern in 

 the sides of the mountains that arise immediately from the 

 sea, where living shellfish may not be found any day of the 

 year. Crows even, and vultures, as well as aquatic birds, de- 

 tach the shellfish from the rocks, and mount with them into 

 the air : shells thus carried are said to be frequently found on 

 the very summit even of the Table Mountain. In one cavern 

 at the point of Mussel Bay," he adds, " I disturbed some 

 thousands of birds, and found as many thousands of living 

 shellfish scattered on the surface of a heap of shells, that for 

 aught I know, would have filled as many thousand wag- 

 gons." * The story, therefore, of the ancient philosopher 

 whose bald pate one of these unlucky birds mistook for a 

 stone, and dropped a shell upon it, thereby killing at once 

 both, is not so tramontane as to stumble all belief 



Land shells furnish a few birds with part of their sus- 

 tenance, and the principal of these are two well known song- 

 sters, the blackbird and the thrush. They, y 



■ " whose notes 



Nice finger'd Art must emulate in vain," 



* Travels in Southern Africa, i. 8. 4to. 1806. 



