The Cowbird: A Parasite 



191 



entire brood of Warblers at whose expense it exists. In addition to this con- 

 sideration, a comparison of the esthetic, sentimental, and educational value of 

 the two groups places the Cowbird in exceptionally ill repute. 



How does the food of a single Cowbird compare in kind and quantity with 

 that of the brood of birds which it has replaced? This question has been 

 answered partially already. In kind, the comparison is favorable; in quantity, 

 unfavorable. One Cowbird certainly does not consume as many injurious 

 insects and seeds of noxious weeds as the three or four song-birds whose place 

 it has taken. 



What, if any, service to man does the Cowbird perform that cannot be 

 performed by parasitized victims? Edward H. Forbush, in 'Useful Birds and 

 Their Protection,' says: "This much-mahgned bird is, nevertheless, an essential 

 part of nature's plan. Birds that rear their own young are confined by neces- 

 sity to a certain radius about their nests; but the scattered bands of Cowbirds 

 form a wandering, unattached hght squadron of insect destroyers, which all 

 summer long can go where their presence is most needed. In the warmer 

 months of the year they feed almost entirely upon insects, but during the 

 colder months they live on seeds." From my own observations, however, 

 places are rare where we find the Cowbird in which we do not also find species 

 of more exemplary habits just as capable as the Cowbird of consuming insects 

 and weed seeds detrimental to human welfare. The numbers of these species 

 would be even more numerous if Cowbirds were exterminated. I doubt 

 whether the "unattached light squadrons" of Cowbirds cover any more terri- 

 tory than is covered by the various species of birds working out from their 

 nests as centers. 



