RED-EYED BRONZED COWBIRD 461 



the chief hosts of this parasite." He says that the species, as a whole, 

 "is definitely known to victimize eleven genera and seventeen species 

 and subspecies, but about 75 per cent of all the eggs are laid in nests 

 of Orioles. I have data on 76 victimized nests all in all and of these 

 no less than 51 belong to four species of Icterus" In addition to those 

 mentioned above, he includes among the victims of the eastern race 

 the western blue grosbeak, Audubon's oriole, western mockingbird, 

 Sennett's thrasher, and the Texas wren. 



Later (1931) he adds three more victims of the eastern race: the 

 Mexican ground dove, the Rio Grande redwing, and Scalter's towhee. 

 And, in another paper (1933), he increases the list to 20 known forms 

 and one hypothetical form, including such large birds as Couch's 

 kingbird, and the Costa Rican Thrush, as well as one vireo and four 

 finches. 



Eggs. — Bendire (1895) describes the eggs of the red-eyed cowbird 

 as "rather glossy; the shell is finely granulated and strong. Their 

 shape varies from ovate to short and rounded ovate. They are pale 

 bluish green in color and unspotted, resembling the eggs of the Black- 

 throated Sparrow andjkBlue^GrosbeakJn^this respect, but are much 

 larger. 



"The average measurement of thirty-eight specimens in the United 

 States National Museum collection is 23.11 by 18.29 millimetres, or 

 0.91 by 0.72 inch. The largest egg of the series measures 24.64 by 

 18.80 millimetres, or 0.97 by 0.74 inch; the smallest, 21.84 by 16.76 

 millimetres, or 0.86 by 0.66 inch." 



These measurements evidently include the eggs of both races of the 

 species. Usually only one egg is laid in a nest of the host, but he 

 mentions a nest of Audubon's oriole that held three eggs of the oriole 

 and three of this cowbird. 



Young.— Friedmann (1929) made the following observations on 

 the growth and development of young red-eyed cowbirds: 



I have not seen a newly hatched Red-eyed Cowbird but have found birds one 

 day old. They resemble young Molothrus ater of corresponding age but are a 

 little larger in size. The skin is orange- pink; the eye-skin greenish-blue; the bill 

 and feet dusky yellowish, the claws light yellow; the gape of the bill swollen and 

 white; the inside of the mouth reddish; the down mouse gray and present on the 

 head, spinal, humeral, alar, and femoral tracts, longest on the head and shortest 

 on the spinal tract; egg-tooth prominent and pyramidal in shape and about 1 mm. 

 high. 



On the second day the birds nearly double in weight; the skin becomes slightly 

 tinged with brownish; no new neossoptiles appear and the old ones apparently 

 do not increase in length. * * * 



A four day old bird had the primaries and secondaries sprouted; the eyes were 

 still closed; feather sheaths were present on all the tracts except the head where 

 the greenish gray skin (formerly orange), was still covered with light mouse gray 

 down. This bird when five days old measured 82 mm. in length, a considerable 



