330 U. S. NATIONAL MUSEUM BULLETIN 211 



The Brewer's blackbird is parasitized by the cowbird. Friedmann 

 (1929) in discussing the host species of the cowbird writes: "Bendire 

 thought this bird was only occasionally imposed upon, but subsequent 

 observations have shown it to be a common host of the Cowbird in 

 the plains and prairies of the west. A. A. Saunders (Auk, XXVIII, 

 no. 1, Jan., 1911, p. 40), writing of the Cowbird in Gallatin County, 

 Mont., says, 'I have found their eggs more often in the nests of 

 Brewer's blackbird than any other species,' and, in the same paper, 

 says of the Brewer's blackbird, 'a large percentage of their nests 

 contain Cowbird's eggs.' " 



Cowan (MS.) writes that on two occasions he has found nestlings 

 of Brewer's blackbird infested with Protocalliphora. Dr. Carlton M. 

 Herman, parasitologist for the California Division of Fish and Game, 

 identified a flea from an abandoned nest at the river-mouth colony 

 in 1945 as Dasypsyllus gallinulae. 



Fall and winter. — In the Salt Lake region of Utah the bird is 

 most abundant during the winter months, according to Lockerbie 

 (MS.), and Behle (MS.) says, "it congregates in winter in the valleys 

 along the Jordan River, in Utah, at ranches where livestock is fed 

 and at dumps and feed yards; there it occurs in great flocks numbering 

 100 to 1,000 individuals." In the Rockport region of Texas, writes 

 Mrs. Jack Hagar (MS.), "many of this species winter in cut-over fields 

 with redwings, cowbirds, and great-tailed grackles," but she believes 

 that "great numbers go on south" of Rockport to winter, as the flocks 

 are larger in spring and fall. In the Houston region, according to 

 G. G. Williams (MS.), "it arrives, usually, within a few days of Novem- 

 ber 1, and disappears in the last half of April. It frequents the grazed- 

 over areas of our wide, flat, treeless coastal plain, as well as the stubble 

 fields of the great rice farms that occupy huge areas here. It is 

 almost never seen in localities where trees predominate. In the 

 northern parts of Harris County (of which Houston is the county 

 seat), where the coastal plain gives way to forest, the species becomes 

 less and less common, and is replaced by the rusty blackbird." 

 Lowery (MS.) writes: "I would regard the Brewer's blackbird as a 

 regular and fairly common winter visitor to southern Louisiana. 

 They seem to be more common in the vicinity of ponds and sloughs 

 which border cane fields and other open situations. I do not believe 

 they are quite as numerous as the rusty blackbird, but they are 

 nevertheless a very prevalent Louisiana winter bird." 



In the fall and winter, the Brewer's blackbird is especially gregarious, 

 associating in flocks composed not only of its own kind but also of 

 other icterids. However, since I have always found it nesting in 

 some sort of colony organization, it might be considered more or less 

 gregarious the year around, in the Carmel region, although the size 



