About Molothrus ater (Boddaert, 1783)
Molothrus ater, commonly known as the brown-headed cowbird, is a member of the icterid family. It shares the general body shape typical of icterids, but is set apart by its smaller size, and finch-like head and beak. Adult males have an iridescent black body paired with a brown head. Adult females are slightly smaller than males, with dull grey overall plumage, a pale throat, and very fine streaking across their underparts. This species measures 16–22 cm (6.3–8.7 in) in total length, with an average wingspan of 36 cm (14 in). Body mass ranges from 30–60 g (1.1–2.1 oz); females average 38.8 g (1.37 oz), while males average 49 g (1.7 oz). Brown-headed cowbirds inhabit open or semiopen landscapes. They often travel in flocks, which may mix with flocks of other bird species: red-winged blackbirds (most commonly in spring), bobolinks (most commonly in fall), common grackles, or European starlings. These birds forage on the ground, and frequently follow grazing animals like horses and cattle to feed on insects stirred up by these larger animals. Their diet consists mainly of seeds and insects; berries are rarely eaten. Before European settlement, brown-headed cowbirds followed bison herds across the North American prairies. Their population grew as settlers cleared forested areas and introduced new grazing animals across the continent. Today, the species is commonly found visiting suburban birdfeeders. In 2012, brown-headed cowbirds in northwest Riverside County, California tested positive for West Nile Virus.
