BIRDS OF PENNSYLVANIA. 
209 
Genus MOLOTHRUS Swainson. 
Molothrus ater (Bodd.). 
Cowbird ; Cow Bunting: ; Cow Blackbird. 
Description {Plate 57). 
Bill short, stout, about two-thirds as long as head ; tail nearly even or very slightly 
rounded ; bill and feet black ; iris brown. 
Male with the head, neck and anterior half of breast deep brown, with slight pur- 
plish gloss ; rest of body lustrous black, with a violet-purple gloss, next to the 
brown, of steel-blue on the back, and of green elsewhere. 
Female, — Plain grayish-brown, lighter on the under parts. 
Young. — Dull dusky-brown above, feathers edged with grayish, lower parts light 
brownish-gray more or less streaked or spotted with darker markings. In the late 
summer and early autumn the young male can often be distinguished by the con- 
spicuous black patches on the body. The female is smaller than the male. An 
adult male measures about 8 inches in length and 13| inches in extent. 
Habitat. — United States, from the Atlantic to the Pacific, north into southern 
British America, south, in winter, into Mexico. 
This well-known bird is a common summer resident in Pennsylvania. 
It arrives here late in March or early in April, and migrates southward 
about the middle of October. These polygamous birds, at all times, are 
gregarious. In the autumn these birds, frequently in company with the 
Crow Blackbirds and robins, collect in large flocks in thickets, where 
they roost during the night. When “ coming in ” to these roosting 
places the flocks of Cowbirds do not scatter and alight in the surround- 
ing trees and bushes, as the Crow Blackbirds are accustomed to do, but 
they fly in a compact body directly to the thick bushy covert, where 
they remain, and unless disturbed are seldom heard to utter their harsh, 
rattling chuckle. The Cowbird builds no nest, nor does she attempt to 
rear her young ; when desirous of laying, she quietly slips away from 
her companions, and finding a nest deposits her egg, and flies off to 
join her comrades feeding in the fields, or, perhaps, assembled in a tree- 
top. Although the Cowbird generally selects the nests of small birds, 
she never gains access to the same by force, but pays her visit when the 
owners are absent. Sometimes birds whose homes have been invaded 
by these feathered parasites abandon their nests, mostly, however (par- 
ticularly if one or more of their own eggs have been deposited), they 
submit to the imposition and rear the young Cowbirds. The Yellow 
Warbler, occasionally, will build a new nest above that in which the un- 
welcome egg is deposited. I have twice found broken eggs of Cowbirds 
on the ground near nests of the Yellow-breasted Chat, and on three oc- 
casions have discovered the shattered remains of these eggs directly be- 
neath the pendant nests of Baltimore Orioles. It may be that these two 
species, sometimes at least, toss out the alien eggs. YTiile it is mostly 
observed that the Cowbird lays in the nests of birds much smaller than 
14 Birds. 
