496 ^ IFE HISTOKIES OF NORTH AMERICAN BIRDS. 



Laramie, Wyoming, which is the latest breeding record I have of this species. 

 Usually only one brood is raised in a season, at 'least in the northern portions 

 of its range. It is occasionally imposed upon by the Cowbird. 



The number of eggs laid to a set varies from four to eight. Sets of five 

 are most often found; sets of six are not unusual, though larger ones are rare. 

 In over two hundred nests seen by me, only a single one contained seven eggs. 

 An egg is deposited daily until the set is completed. Incubation lasts about 

 fourteen days, and this duty is performed almost exclusively by the female. 

 The young are large enough to leave the nest in about sixteen days, and after 

 they are able to care for themselves they collect into small flocks and rove about 

 the country until the fall migration begins, when they collect into large assem- 

 blies, and about the latter part of September begin to move southward. Birds 

 wintering along our northern border appear to be nearly all adult males. 



The eggs of Brewer's Blackbird are mostly ovate, less often short ovate, and 

 rarely elliptical ovate in shape. The shell is strong, not as finely granulated as 

 in the preceding species, and when fresh the eggs are rather glossy. Compared 

 with those of the Busty Grackle, they show very little resemblance, both ground 

 color and markings being very different, and the majority are much darker. The 

 ground color, when plainly visible, is usually pale gray white, less often pale 

 greenish white, a color that is difficult to exactly describe. This is mostly 

 profusely blotched, marbled, streaked, and spotted, with irregularly shaped 

 markings of seal, walnut, liver, and clove brown, mixed with lighter shades of 

 russet, cinnamon rufous, fawn color, and lavender. Some specimens are more 

 or less streaked with irregular lines and tracings, resembling those found on 

 some eggs of the Bed-winged Blackbird, while in others the markings are heavy 

 and so uniformly distributed that the ground color is entirely hidden. In a few 

 they are fine and minute, resembling those found on the eggs of our well-known 

 Brown Thrasher. In fact, there is an endless variety of styles of markings, and 

 two sets are rarely found which are marked exactly alike. 



The average measurement of two hundred and forty-five specimens in the 

 United States National Museum collection 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 milli- 

 metres, or 1.10 by 0.79 inches; the smallest, 20.83 by 15.49 millimetres, or 0.82 

 by 0.61 inch. 



Of the type specimens, No. 20243 (PL 7, Fig. 17), from a set of four eggs, 

 represents one of the heavily marked and smaller-sized specimens; No. 20246 

 (PL 7, Fig. 18), from a set of five, represents one of the lighter-marked eggs, in 

 which the ground color is plainly visible; No. 20252 (PL 7, Fig. 19), also from 

 a set of five, shows another style of markings; and No. 20264 (PL 7, Fig. 20), 

 likewise from a set of five, represents still another type. These eggs are all in 

 the Bendire collection. The first three were taken by the writer near Camp Har- 

 ney, Oregon, on May 23, 1875, May 23, 1876, and May 16, 1877, respectively, 

 and are selected out of a large number of nests examined. The last was taken 

 by me near Fort Klamath, Oregon, on May 22, 1883, and represents one of the 

 more common styles of markings. 



