Coiv -Birds. 



237 



XXXV. 



INDIRECT EVIDENCE FROM THE AMERICAN COW-BIRDS. 



We have already referred to one point in which 

 a striking commentary on certain actions of the 

 common cuckoo is found in the molotlirus or cow- 

 bird — an American species alUed to the starhngs. 

 They are called cow-birds because they are often 

 seen on the backs of these animals or among the 

 cattle on the ground picking off insects that are 



COW-BIRDS ON COWS' BACKS AFTER INSECTS. 



there. . . .* We may here indicate some other 

 points which will be suggestive and illustrative of 

 certain traits to be found probably more or less in 

 all parasitic birds. 



I. The cow-bird's eggs not only vary greatly in 



* H. Nehrling, ii, p, 31. 



