Cowbird. 141 



great, clumsy cowbird pressing closely after the parent 

 birds for each newly-found morsel. 



Few birds in whose nest the cowbird has succeeded in 

 placing its eggs lay their fullest complements. Even 

 when the usual number is deposited, the rapidly growing 

 interloper, which commonly emerges first from the shell, 

 robs the. rightful offspring until they starve before they 

 are old enough to leave the nest, or else until they are 

 weakly specimens to begin the struggle for existence. 

 The- species selected by the cowbird in one locality may 

 be almost exempt in another locality. In my former 

 home in an adjoining county, the brown thrasher is very 

 rarely selected, but in my present vicinity I have met 

 several instances of such a selection. It is evident that 

 upon many species given in lists of birds imposed upon 

 by the parasite, the cowbird intrudes its Qgg only rarely, 

 and hence a very large list can be formed. The warblers, 

 vireos, sparrows, and smaller flycatchers are the heaviest 

 sufferers. In my observation, the wood thrush, towhee, 

 field and chipping sparrows, yellow-breasted chat, and 

 the Maryland yellowthroat are oftenest selected to bear 

 the burden of rearing the young of the cowbird. 



The female cowbird generally watches her opportunity, 

 and slips into the nest while the owner is absent in search 

 of food or recreation. Eobert Eidgway, in "Natural 

 History Survey of Illinois," Vol. I, thus speaks of the 

 actions of the cowbird : <' It is interesting to watch the 

 female when she is searching for a nest in which to deposit 

 the Qgg she is about to lay. She hunts stealthily through 

 the woods, usually among the undergrowth, and when a 

 nest is discovered, patiently awaits from a convenient 

 hiding place the temporary absence of the parent, when 

 the nest is stealthily and hastily inspected, and if found 

 suitable she takes possession and deposits her Qgg, when 

 she departs as quietly as she came." In some instances, 

 however, it is probable that the intruder drives the lawful 

 occupant from the nest and makes a place for her Qgg by 

 force. Frequently, also, the cowbird will eject one or 

 more eggs of the owner to make room for her egg^ or to 

 deceive the owner and leave the same number of eggs as 

 were in the nest before her visit, and as frequently the 



