The Cowbirds 



in ten or eleven days, usually, therefore, two or three days before those 

 of the foster mother, and the infant Cowbird thus gains an advantage 

 which he is not slow to improve. His loud clamoring for food often drives 

 the old birds to abandon the task of incubation; or if the other eggs are 

 allowed to remain until hatched, the uncouth stranger manages to usurp 

 attention and food supplies, and not infrequently to override or stifle the 

 other occupants of the nest, so that their dead bodies are by-and-by 

 removed to make room for his hog- 

 ship. It is asserted by some that in 

 the absence of the foster parents the 

 young thug forcibly ejects the right- 

 ful heirs from the nest, after the 

 fashion of the Old World Cuckoos. 

 I once found a nest which contained 

 only a lusty Cowbird, while three 

 proper fledglings clung to the shrub- 

 bery below, and one lay dead upon 

 the ground. 



When the misplaced tenderness 

 of foster parents has done its utmost 

 for the young upstart, he joins him- 

 self to some precious crew of his own 

 blood, and the cycle of a changeling 

 is complete. 



There are endless details and 

 variations to be noted in this exhibi- 

 tion of parasitism, here so hastily 

 reviewed. Much remains yet to be 

 learned by methodical observation, 

 particularly of the western varieties. 

 Especially interesting is the psycho- 

 logical reaction of the various victims 

 to the infamous imposition practiced 

 or intended. Major Bendire has listed 1 ninety species of involuntary 

 hosts of the better known M. ater, and twenty-five for M. a. obscurus. 

 Of these the most conspicuous victims upon our borders are the Arizona 

 Least Vireo {Vireo belli arizonae), Lucy's Warbler {Vermivora luciae), 

 and the Western Chat {Icteria virens longicauda) It is rare to find 

 Least Vireos' nests which have not been victimized, and the destruction 

 caused to this one species is enormous. Sometimes the birds cease 

 laying upon the advent of the foreign egg, and sometimes they desert 



'"The Cowbird" by Charles Bendire, Rep. of National Museum, 1893 (pub. 1895), p. 594-5. 



Taken in Arizona Photo by the Author 



A DOORSTEP CHILD 



THIS EGG OF THE DWARF COWBIRD RESTS ON THE SKIRTS 



OF A LUCY WARBLER'S NEST. THE CRANNY 



OCCUPIED BY THE NEST WAS TOO SMALL 



TO ACCOMMODATE THE INTERLOPER 



79 



