DESTRUCTION OF MOLLUSKS. 53 



in damp places, and were found in stomachs of Grows snot near gar- 

 bage heaps in the vicinity of Washington. In March, October, and 

 December, the remains consisted mainly of marine crabs, doubtless 

 thrown up by the sea, and captured dead or alive by the Crows along 

 the seashore. One stomach taken in December contained barnacles 

 amounting to 40 percent of the contents. This food, except the craw- 

 fish, has no economic significance, and the greater part may be safely 

 counted as carrion or offal. Crawfish, on the other hand, are capable 

 of doing considerable damage, particularly by tunneling dams or 

 embankments, and by throwing up mud 'chimneys' on low grass 

 lands. It is by no means certain what proportion of the remains found 

 in stomachs should be regarded as carrion, but since fragments of 

 crawfish occurred in 123 stomachs it is extremely probable that the 

 Crows have learned where and how to catch these crustaceans alive. 

 In the month of May 83 stomachs, or almost 1 in every 4, contained 

 their remains, the average for these exceeding 7 percent, while the 

 average of all the stomachs, that is, the percentage of the entire food 

 for the month, was a little more than 1J percent (1.6 percent). JSTo 

 other month shows so large a record of crawfish, although in April 

 they were found in 9 stomachs out of 42, and the average for the 9 was 

 over 4 percent. 



Of course Crows on the seashore get large numbers of crustaceans, 

 both alive and thrown up dead by the waves, but in general the con- 

 sumption of this food has little bearing on the economic status of the 

 Crow. 



DESTRUCTION OF MOLLUSKS. 



The presence of mollusks in the stomachs of crows was determined 

 in most cases by fragments of their shells, and the utmost care was 

 necessary to determine in each case whether these bits of shell were 

 parts of entire animals taken as food or simply part of the gravel so 

 generally swallowed to aid digestion. As a rule the latter was assumed 

 to be true whenever the fragments had worn edges, otherwise the 

 former. Sometimes entire snails were found, and occasionally large 

 fragments of fresh or salt water bivalves, but in the majority of 

 stomachs no such decisive matter was present. 



Among the Crows taken at a distance from the sea the traces of 

 mollusks were confined to land snails (mainly Helix) except in one 

 or two cases where fragments of shells of fresh- water mussels ( Unio) 

 occurred. Crows have been credited pretty generally with the habit 

 of lifting clams, mussels, and other shellfish high in the air and drop- 

 ping them on hard objects in order to break the shells and get at the 

 contents. An observation on this subject illustrating the acuteness 

 and intelligence of the Northwest Fish Crow {Corvus caurinus) was 

 published by H. W. Henshaw in the Youth's Companion, January 9, 

 1890. Mr. Henshaw says : 



