THE COWBIRDS. 



599 



out and broken, and occasionally every one, the foster parent sitting 

 on the parasite's eggs alone. Among other instances I found this to be 

 the case in a nest of the Plumbeous Gnatcatcher placed in a thick 

 mistletoe bunch growing from a limb of a mesquite tree about 15 feet 

 from the ground, and well hidden. I first observed the nest on June 

 10, 1872, when it contained a single egg; on visiting it again on the 

 17th, the female was sitting on a couple of Dwarf Oowbird'S eggs alone, 

 and on looking on the ground I found the remnants of 3 eggs, which 

 evidently had been thrown out. Bullock's Oriole may occasionally rid 

 herself of the parasitic egg; at any rate I noticed the remains of such 

 a one lying under a nest of this species with portions of one of her 

 own. This nest contained only 3 eggs of the rightful owner, and the 

 bird was sitting on these. The largest number of Dwarf Cowbird's 

 eggs found by me in one nest was 3, that of a Desert Song Sparrow, 

 and all its own eggs were missing. I several times found nests con- 

 taining single eggs of this parasite abandoned, and also picked up 2 

 uninjured from the ground where they evidently had been dropped by 

 the bird, not finding a suitable nest in time to deposit them. None of 

 the young of the foster parents seem to survive the advent of a young 

 Cowbird in their nest longer than two or three days; they are starved 

 by that time by their more vigorous and voracious foster brother. After 

 the young Dwarf Cowbird is old enough to care for itself it abandons its 

 foster parents and seeks the company of its own kind, gathering in small 

 bands and roving from place to place. Later in the season, about the 

 latter part of October, these gather into larger fiocks, associate at this 

 time with other congenial species, and shortly after return to their 

 winter homes in Mexico. 



In general appearance and shape the eggs of the Dwarf Cowbird 

 resemble those of the former, and the same description will answer for 

 both, but they appear on an average to be somewhat less heavily 

 spotted, which gives them a lighter appearance; and they are also 

 considerably smaller. 



The average measurement of 37 specimens in the F. S. National 

 Museum collection is 19.30 by 14.99 millimeters, or 0.76 by 0.59 inch; 

 the largest egg in this series measures 20.57 by 15.19 millimeters, or 

 0.81 by 0.61 inch; the smallest 18.03 by 13.74 millimeters, or 0.71 by 

 0.54 inch. 



CALLOTHRUS ROBUSTUS (Cabauis). Red-eyed Cowbird. 



Ps((rocoUnus ceneus, Waglkr, Isis, 1829, 758. 



CaJlofhrus rohushis, Ridgway, Manual of North American Birds, 1887, 589. 

 (B — , C — , R 259, C 315, U 496. ) 

 Adult males : Head, neck, back, and lower parts uniform glossy black, 

 with a soft, bronzy luster, duller on head; lesser and middle wing 

 coverts, outermost scapulars, and rump glossed with violet; v.ings in 

 general, upper tail (;overts, and tail glossy blue-black, changing to 

 greenish; iris bright red. Length about 9-9.50, wing 4.60-4.80, tail 



