This section is from "The American Cyclopaedia", by George Ripley And Charles A. Dana. Also available from Amazon: The New American Cyclopędia. 16 volumes complete..
Cow Bird, Or Cow Bunting, a bird of the genus molothrus (M. pecoris. Swains.). In the genus the bill is short and stout, elevated at the base, and advancing on the forehead; wings long and pointed, first and second quills the longest; tail moderate and nearly even. Of the few species, the above is the only one found in the United States; it is about 8 inches long and 12 in alar extent; in the male the prevailing color is shining black, with a purplish and steel-blue gloss; the head, neck, and anterior part of breast, light chocolate brown; the female is light olivaceous brown; bill and feet black. It is found throughout the United States from the Atlantic to California, though probably not on the Pacific coast; it frequents fields and farmyards, following cattle, sometimes picking ticks from their backs, and at others feeding on the seeds, worms, and insects contained in their dung; large flocks migrate to the north in spring to breed, returning in autumn. The females have the habit of dropping their eggs, generally singly, into the nests of other smaller birds, as sparrows, warblers, and flycatchers; in New England the summer yellow bird's nest is most frequently selected.
The eggs thus stealthily dropped are of about the same size as the true ones, and are more quickly hatched by the foster parents; of course, with this habit the cow birds do not pair, nor display the lasting attachment of ordinary birds. The European cuckoo has the same habit of abandoning her progeny to the care of strangers; but this is the more remarkable in the cow bird, as belonging to a family proverbial for the ingenuity with which their nests are constructed. If the cow bird's egg be deposited in a newly finished but empty nest, the makers generally abandon it; if in a nest already containing eggs, it is usually allowed to remain, though the makers are probably often aware of the intrusion. The yellow bird has a way of disposing of the strange egg which will be noticed under that title. The egg is pale grayish blue, with amber-brown dots and streaks, and the young is hatched in about a fortnight, the other eggs remaining un-hatched; the intruder is fed by the foster parents, to the neglect of their own eggs, which, when the contained embryo has perished, are cast from the nest; and it is cared for long after it has left the nest. This species has no song, but a low muttering chuckle. The flesh is esteemed as food, and many are shot for this purpose in the southern states.
They roost among the reeds in swampy places, and feed in immense flocks, often in company with the red-winged blackbird and other troopials.
Cow Bird (Molothrus pecoris).