402 
SYSTEMATIC SYNOPSIS. —FASSEBES— OSCINES. 
has lately been added ; there are several others in the warmer parts of America, all of the same 
irregular and objectionable tendencies. 
Analysis of Species and Varieties. 
{f , steely black with, brown head. 
Larger : ^, wing over 4.00 ; tail over 3.00 ; $ , wing about 3.75; tail about 2.75 ater 313 
Smaller: cf, size of $ of the foregoing . obscurus 314 
(f, brassy black, including head ; eyes red; wing near 5.00; tail nearly 4.00 ceneus 315 
313. M. a'ter. (Lat. ater, black. Fig. 258.) Common Cowbird. Cuckold. adult: Lus- 
trous green-black, with steel-blue, purple, and violet iridescence. Head and neck deep wood- 
brown, with some purplish lustre. Bill and feet black. Length 7.50-8.00; extent 13.50 j 
wing about 4.50, at least over 4.00 ; tail about 3.25 ; bill 0.70 ; tarsus 1.00-1.10. 9 , adult : 
An obscure-looking bird, dusky grayish-brown, nearly uniform, but paler below than above, 
where most of the feathers have dusky centres, and most of those of the under parts with dark 
shaft lines ; giving a somewhat streaky appearance. There is some gloss on the upper parts, 
particularly on the wings and tail, where a slight greenish lustre is usually evident. Bill 
blackish-brown, paler below; feet blackish -brown. Smaller than the ^. Length 7.00-7.50 ; 
wing about 3.75; tail 2.75. Young ^ 9 : Similar to the 9 adult; still duller, and more 
variegated ; upper parts dusky brown, the 
feathers skirted with gray, producing a set 
of semicircles on the back; below, pale 
grayish, or even ochrey-brown, everyM'here 
streaked with dusky. The sexual diiference 
in size soon appreciable, and the black of 
the soon begins to apj)ear in patches. 
N. Am. at large ; migratory, abundant, 
gregarious, polygamous, parasitic. The 
singular habits of this bird, shared by others 
of the genus, form one of the most inter- 
esting chapters in ornithology. Likfe the 
European cuckoo, it builds no nest, laying 
Fig. 258. — Cowbird, reduced. (Sheppard del. its eggs by stealth in the nests of various 
Nichols sc.) other birds, especially warblers, vireos, and 
sparrows ; and it appears to constitute, furthermore, a remarkable exception to the rule of 
conjugal affection and fidelity among birds. A wonderful provision for the perpetuation of the 
species is seen in its instinctive selection of smaller birds as the foster-parents of its offspring ; 
for the larger egg receives the greater share of warmth during incubation, and the lustier young 
cowbird asserts its precedence in the nest ; while the foster-birds, however reluctant to incu- 
bate the strange egg (their devices to avoid the duty are sometimes astonishing), become assid- 
uous in their care of the foundling, even to the neglect of their own young. The cowbird's 
egg is said to hatch sooner than that of most birds : this would obviously confer additional 
advantage. The list of birds in whose nests cowbirds' eggs have been found includes a large 
number of finches, warblers, greenlets, flycatchers, etc. ; there seems to be really little choice. 
While small species are usually victimized, this is not always the case. I have found eggs in 
nests of the kingbird and towhee bunting. In the West, where cowbirds swarm about the ranches 
and settlements, it is the rule, I almost said, to find their eggs in nests of the prairie Frin- 
gillidce, etc. The egg is usually single; sometimes 2, 3, even 4 are found in a nest; they 
range from 0.80-1.00 in length, by 0.65-0.70 in breadth, and are white, fully speckled* and 
dashed with browns and neutral tints. 
314. M. a. obscu'rus. (Lat. obscurus, dark.) Dwarf Cowbird. Similar ; smaller ; ^ the size 
of 9 M. ater; 9 under 7.00; wing 3.33; tail 2.33. The difference is strongly marked, and 
