Shiny Cowbird illustration
Birdsong field guide

Shiny Cowbird

Molothrus bonariensis

A medium-sized icterid renowned for its glossy iridescent plumage and its role as a prolific obligate brood parasite. It is a highly adaptable species that has significantly expanded its range across the Americas.

What it sounds like

A complex series of bubbly, liquid gurgles and squeaks, often ending in a high-pitched, ascending whistle.

Reference call, compare with what you heard
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Rec. Cristian Pinto Fernandez · ChileCC BY-NC-SAXeno-canto

Field notes

  • It is an obligate brood parasite, documented laying eggs in the nests of over 250 different host bird species.
  • Females often engage in 'egg-pecking,' where they puncture or remove host eggs to reduce competition for their own chicks.
  • The species displays strong sexual dimorphism; males are a silky, iridescent purple-black, while females are a duller grayish-brown.
  • Egg appearance is highly polymorphic, ranging from immaculate white to heavily spotted, likely an adaptation to mimic diverse host species.
  • Originally native to South America, it successfully colonized the West Indies and reached the southeastern United States by the 1980s.
Habitat
Open fields, pastures, agricultural lands, forest edges, and suburban gardens.
Range
Widespread across South America, the Caribbean, and the southeastern United States.

Similar & commonly confused birds

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