Appearance
The male shiny cowbird is all black with an iridescent purple-blue gloss. The smaller female is dark brown in plumage, paler on the underparts. She can be distinguished from the female brown-headed cowbird by her longer, finer bill, pale supercilium and stronger face pattern. There is an all-black plumage variation, and the northern subspecies "M. b. cabanisii" of Panama and northern Colombia is paler than the nominate "M. b. bonariensis". Juveniles are like the female but more streaked below. There is some variation in size across the range, with the race of "M. b. minimus" from northern South America and the West Indies being the smallest at 31 to 40 g and 18 cm in length and "M. b. cabanisii" being the largest at 55 to 65 g and 22 cm on average.
Behavior
The male’s song is a purr and whistle, "purr purr purrte-tseeeee". The male’s call is a sharp whistled "tsee-tsee", but the female makes a harsh rattle.
Reproduction
Like most other cowbirds, it is an obligate brood parasite, laying its eggs in the nests of many other bird species, such as the rufous-collared sparrow and the masked water tyrant. The eggs are of two types, either whitish and unspotted, or pale blue or green with dark spots and blotches. The host’s eggs are sometimes removed, and if food is short their chicks may starve, but larger host species are less affected. The incubation period of 11–12 days is shorter than that of most hosts. Extermination of the shiny cowbird within the tiny range of the pale-headed brush finch has resulted in a population increase in this critically endangered species.Food
This abundant and gregarious bird feeds mainly on insects and some seeds, including rice, and forages on the ground or perches on cattle.References:
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