BLACKBIRDS, ORIOLES, ETC.: COWBIRD 
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eggs in the nests of ninety odd kinds of smaller birds, their large young 
crowding the rightful nestlings from their nests and making the enforced 
foster parents endless trouble in caring for them. They have been 
found by Mr. Jensen putting their eggs in the nests of House Finches, 
1. Cowbird. 2. Dwarf Cowbird. 
Shaded area shows general range. Triangles mark summer records 
Western Chipping Sparrows, and Brewer Sparrows; and by Mr. 
Ligon, in wooded canyons at about 6,500 feet, in the nests of Plumbeous 
Vireos. At Chloride he saw two males and a female locate a Vireo’s 
nest, after which one of the males picked up two of the three Vireo’s 
eggs and dropped them to the rocks ten feet below, apparently to make 
room for the intruders. 
Although it leads to no family life, the formal courtship of the 
Cowbird is not without interest. The song and accompanying display 
