24 WISCONSIN BIRD-STUDY BULLETIN. 



COWBIED, cow BLACKBIRD, COW BUNTING. 



Abundant S'mnmer resident; length about eight inches; sexes quiL 

 similar; nest none; eggs eight to twelve. 



The male eowbird has a blackish brown head and neck. The rest 

 of the body is a glossy black with bright bluish and greenish burnisli- 

 ings. 



The female is a dark brownish gray, lighter on the under parts. 



The cowbirds arrive in Wisconsin about the first week in April. 

 They are at first in large flocks. The flocks break up as the breeding 

 season approaches and the birds scatter in small companies of abovit 

 a dozen each. 



The cowbirds have a varied diet: they eat small seeds, grains and 

 berries for the vegetable part and grasshoppers, beetles, flies and other 

 insects for the animal part of their ration. 



Their fondness for insects has led them to hunt their food about 

 cattle. Frequently one may see the cows in the pasture attended by 

 a small flock of these birds that wall^ about them, on the ground an<l 

 even perch up)on their backs and hunt there for parasitic insects. Jt 

 is this habit that has given them their common name. 



The most peculiar and interesting habit of the cowbirds is the 

 scheme they have adopted of putting their families out to be reared 

 by other birds. 



As stated in the first paragraph, they build no nest at all, yet t'.e 

 female lays from eieht to twelve eggs. 



When the nesting time of the other birds has come, Mrs. Cowbird 

 lurks stealthily through trees and bushes. Her one thought, nov/, is 

 to discover a bird's nest. It does not matter much whose nest it is, 

 providing it is not the nest of too large a bird. The cowbird under- 

 stands that if her egg is placed in the nest of a bird much larger than 

 herself, the nestling from her egg will have no advantage over those 

 from the other eggs : in fact, that it may even be at a disadvantage. 



Although such large birds as the mourning dove, red-winged black- 

 bird and meadow lark are imposed upon, it is usually a smaller bird 

 that suffers. 



There is another thing that the cowbird understands and that is 

 that her egg must not be placed in a nest upon which the mother bird 

 has begun to sit. That would give the regular eggs an advgintage o^^er 

 her egg. 



She examines the nest when found, and, if empty, or containing 

 fewer than the regular number of eggs, she lays an egg in the nest 

 and quietly steals away. She does not always leave the eggs in the 

 nest as she found them; sometimes she throws some of them out; 

 sometimes she pierces some or all of them with her claws or bill, evi- 

 dently for the purpose of injuring them. Mr. Bendire, who has ex- 

 amined a very large number of nests containing one or more cow- 



