430 U. S. NATIONAL MUSEUM BULLETIN 211 



As evidence of polyandry, Friedmann (1929) relates the following 

 experience: 



A pair with whose territory I was fairly familiar was noted several times and 

 each time there was just a single male and a single female. The male used to 

 stay in his singing tree and so was easy to find. The female, when wanting her 

 mate, would fly into the open and give her flight rattle. The male would quickly 

 take off after her. One day it was noted that when the female called for her 

 mate he came directly from his favorite perch as always but another male, new 

 to the territory, also answered her summons. This interested me not a little 

 and I went back there the next day and waited for the female to call for her 

 mate. Again both males answered her summons, the original male coming as 

 always from his singing tree and the new one from a tall tree near a railroad 

 track. Some time later in the afternoon the original male was seen again in 

 his singing tree and the second male was noted in the tree from which he had 

 flown in answer to the call of the female. On the next two successive days this 

 male was seen in or near this tree and it certainly looked as though he had 

 established himself there. A week later the place was revisited and both males 

 were found, each in his own tree and both again answered the summons of 

 the female. 



This apparently was a case of polyandry — an unmated male established him- 

 self in the territory of a mated pair. He was not there originally as the pair 

 had been watched considerably before his advent. The original male seemed 

 not to mind the presence of the other. However, no actual intercourse between 

 any of the birds was observed. 



Mrs. Nice (1937) writes: "With a small population of Cowbirds, 

 this investigator found the species predominantly monogamous, with 

 some tendency towards polyandry. But here on Interpont, with an 

 abundance of Cowbirds, promiscuitj 7 prevails just as the older writers 

 maintained. A banded male has been seen with three different 

 banded females and one unbanded female, while banded females are 

 seen with varying numbers of males from one to five." And Forbush 

 (1927) says: "Cowbirds are free lovers. They are neither polyga- 

 mous nor polyandrous — just promiscuous." 



Nesting. — The remote ancestors of the cowbirds may have been, 

 and probably were, nest builders, incubating their eggs and rearing 

 their own young, as other birds do. It is difficult to imagine how 

 they could have evolved otherwise. I once saw a poor apology for 

 a nest that I thought might have been built by a cowbird. While 

 driving across the North Dakota prairies, on June 14, 1901, we saw 

 a crude bunch of straws and dried grasses lodged in a bush; it had 

 the appearance of a roughly built nest, but it was too large and bulky 

 and too loosely and carelessly put together to have been built by 

 any other bird in that region; a hollow in the center held a single egg 

 of a cowbird. As cowbirds were abundant in that section and other 

 nesting birds were scarce, it occurred to me that perhaps a cowbird, 

 being unable to find a suitable host, had made an attempt to build 

 its own nest. It is more than likely, of course, that some small 



