BREWER'S BLACKBIRD 313 



and other males as well as her mate respond; among the males, rushes 

 and threat displays are frequent. These advances by intruding 

 males and the guarding actions by the mate, which begin in Phase 1, 

 reach their height of occurrence in Phase 2, which, from the beginning 

 of actual nest construction to the completion of the clutch, lasts 

 about 10 days or 2 weeks, at the most. 



Eggs. — The number of eggs in a clutch varies from 3 to 7; Bendire 

 (1895) and Hoffmann (1927) are the only writers I know who have 

 given a number as high as 8. Cowan (MS.) says that in British 

 Columbia "5 eggs is the most frequent number." Dawson and 

 Bowles (1909), referring to the species in Washington, and Dawson 

 (1923), referring to California, give the number per set as "4-7, 

 usually 5 or 6." La Kivers (1944) in a month of field study near 

 Reno, Nev., found 107 nests containing a total of 521 eggs. The 

 clutches were divided as follows: 23 with 3, 21 with 4, 22 with 5, 29 

 with 6, and 12 with 7 eggs each. 



Ray (1909) found numerous nests of this species in the region about 

 Lake Tahoe, Calif., in May and June 1909, nearly all of which were 

 in small "tamarack pines, often mere saplings, from four to fifteen 

 feet up, and but poorly concealed" (a notable exception was one nest 

 placed on a wharf piling which was standing in water 3 feet deep). 

 He says that "five was the usual complement of eggs, tho often four 

 or six, and sometimes only three." The eggs he examined "showed 

 great variation in size, shape and coloring." 



Dawson (1923) also notes variation in pattern and coloration. 

 He writes that the eggs present — 



Two divergent types of coloration, with endless variations and intermediate 

 phases. Light type: ground color light gray or greenish gray, spotted and 

 blotched with grayish brown or, more sharply, with sepia. Eggs of this type 

 rehearse relationships, now with the Quiscaline Grackles, and now with the 

 Yellowheads (Xanthocephalus xanthocephalus) , or the Cowbirds (Molothrus ater). 

 An egg in the M. C. O. collection has a background of pale niagara green sharply 

 spotted with a blackish pigment which tones out to dusky drab, and is thus 

 indistinguishable from the egg of an Agelaiine Blackbird. Dark type: Ground 

 color completely obscured by overlay of fine brown dots, or else by confluent 

 blotches of Rood's brown, walnut brown, or cameo brown. 



Bendire (1895) writes: "The average measurement of two hundred 

 and forty-five specimens in the United States National Museaum col- 

 lection is 25.49 by 18.60 millimetres, or about 1 by 0.73 inch. The 

 largest egg in this series measures 27.94 by 20.07 millimetres, or 1.10 

 by 0.79 inches; the smallest, 20.83 by 15.49 millimetres, or 0.82 by 0.61 

 inch." 



Incubation. — Bendire (1895) states that the incubation period is 

 14 days. Saunders (1914) says that the eggs hatch in 12 days in 

 Montana. 



