BREWER'S BLACKBIRD 325 



tucker-tucker, or tit-tit-tit — used by males accompanying the elevated 

 tail display (see under "Spring" and "Courtship"); sometimes these 

 utterances resemble the kit notes. Peeping sounds — made by young 

 nestlings. Tut-utz-utz — a low, hoarse, scratchy series of rhythmic 

 notes, the "begging" notes of older nestlings and of fledglings; when 

 the parents are away foraging the fledgling utters the "location" note, 

 but when the adult arrives the young bird changes to this "begging" 

 note in anticipation of being fed. 



Field marks. — The species most easily confused with the Brewer's 

 blackbird in the field are the redwing and tricolored redwing, the rusty 

 blackbird (Euphagus carolinus), the bronzed grackle (Quiscalus quis- 

 cula), and the cowbird {Molothrus ater). Peterson (1941) says that 

 the male rusty blackbird in summer plumage has "dull greenish instead 

 of purplish head reflections [as in Brewer's]. The iridescence is almost 

 lacking [and is] not noticeable as in the Brewer's Blackbird or the 

 Bronzed Grackle." The rusty and Brewer's blackbirds are about the 

 same size but the bronzed grackle is noticeably larger and has a 

 "longer tail, which is somewhat wedge-shaped." The female Brewer's 

 has a dark brown iris in contrast to the pale yellow iris of the female 

 rusty blackbird. In winter the female Brewer's blackbird does not 

 have the rusty wash, as do rusty blackbirds of both sexes. But the 

 immature male Brewer's in the first winter plumage, according to 

 Ridgeway (1902), has the "feathers of head, neck, back, scapulars, 

 chest, and sides narrowly tipped with grajnsh brown." There is the 

 possibility that in this plumage, also, the male might be confused with 

 the male rusty blackbird in winter plumage. But the tipping is more 

 grayish and less rusty brown. The male redwing and tricolored red- 

 wing are obviously distinct from the Brewer's. Hoffman (1927) points 

 out the distinctive marks for females: "The unstreaked breasts dis- 

 tinguish the Brewer Blackbirds from female Redwings [and also, it 

 may be added, tricolored redwings], and the greater size, darker 

 plumage and long, sharp-pointed bills distinguish them from the female 

 Cowbirds. The yellow (apparently white) eye and long sharp- 

 pointed bill distinguish the male Brewer from the male Cowbird." 



Enemies. — La Rivers (1944), reporting on one nesting season of 

 Brewer's blackbirds near Reno, Nev., found that 107 nests held 521 

 eggs, 205 of which resulted in fledglings that left the nest safely, a 

 mortality of 60.65 percent. "Twenty-three eggs were known to be 

 sterile, but other sterile eggs were obviously among those which dis- 

 appeared without known cause. The total number of eggs and nest- 

 lings unaccounted for because of unknown predation, amounted to 83, 

 but the remaining 233 could nearly all be ascribed with certainty to 

 one of 23 known factors, 21 of which were biologic, the other two 

 climatic [i. e., wind and hail]." 



