igo Bird -Lore 



believe that in some localities the percentage of parasitism approaches 

 very nearly loo per cent. 



The status of the Cowbird cannot be determined without vie^sing it from 

 an economic standpoint and noting its relation to agriculture. Four questions 

 must be answered in doing this: (i) Of what does the food of the Cowbird 

 consist? (2) Of what does the food of its victims consist? (3) How does the 

 food of a single Cowbird compare in kind and quantity with that of the brood 

 of birds it has replaced? (4) What, if any, service to man does the Cowbird 

 perform that cannot be performed by victimized species? 



According to Barrows, in 'Michigan Bird Life,' the food of the Cowbird is 

 22 per cent animal matter and 78 per cent vegetable matter. Of the 22 per 

 cent of animal matter, 20 per cent consists of insects as follows: grasshoppers, 

 which during August furnish 45 per cent of the food of the species, 10 per cent; 

 weevils, 2 per cent; caterpillars, including cutworms and army worms, 2 per 

 cent; and wasps, bees, ants, and miscellaneous insects, 6 per cent. The vege- 

 table matter consists mainly of weed seeds and grain, the former predominating. 

 The latter is largely waste grain, but some is from newly sown fields. I have 

 also seen young Cowbirds accept wild fruit, such as mulberries and raspberries 

 from their foster parents. Undoubtedly, the food habits of the Cowbird are, 

 on the whole, beneficial. 



In answer to our second question above, we learn from Barrows, in 'Mich- 

 igan Bird Life,' and Butler, in 'Birds of Indiana,' of what the food of some of 

 the birds commonly victimized by the Cowbird consists. The Towhee feeds 

 mainly upon weed seeds and insects. Although it is fond of wild fruits and 

 eats almost everything from strawberries and blackberries to wild cherries and 

 grapes, it does no damage to cultivated fruits and plants. Owing to the nature 

 of its haunts, it is not as beneficial as many other species. In view of the fact 

 that it frequently raises two or more Cowbirds along with one or more of its 

 own young, it is questionable whether much economic loss results from its 

 victimization by the Cowbird. 



All the Sparrows, with the exception of the English Sparrow, are very 

 beneficial in their eating habits. Weed and grass seed, an immense number of 

 injurious insects, and small wild fruit constitute the bulk of their food. It is 

 easy to see the harm done by the Cowbird when we know, for example, that 

 the Song Sparrow raises more Cowbirds than any other species and that, as a 

 rule, one Cowbird is raised at the expense of an entire brood of Sparrows. 



The food habits are uniformly beneficial. They consume largely insects, 

 spiders, small wild fruits, and insect eggs. They usually make use of food most 

 easily obtainable. Forbes has shown in one case that where an orchard was 

 infested with canker-worms, these larvae formed two-thirds of the food of the 

 Yellow Warbler. While Cowbirds are voracious feeders, and one of them un- 

 doubtedly destroys many more harmful insects than a single Warbler, the good 

 done by one Cowbird by no means balances with that accomplished by the 



