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Shiny Cowbird | Molothrus bonariensis
Glanskoevogel | Tordo renegrido | Chupim
The Shiny Cowbird is the most widespread cowbird of South America and a brood parasite that lays its eggs in the nests of more than 250 bird species. With deforestation and the spread of farmland it has expanded strongly since the twentieth century, reaching the Caribbean and the south-eastern United States. In the guide area it occurs in all four mainland countries.
Voice
The male's song is a flowing series of bubbling, whistled notes ending in a high whistle, delivered with feathers puffed out. The call is a high chip; in flight a thin whistle.
Recording: Cristian Pinto Fernandez — CC BY-NC-SA 4.0 · xeno-canto
Identification
17–21 cm; the male is larger than the female. The male is entirely black with a strong purplish-blue gloss, the female greyish brown, slightly paler below, with a faint pale supercilium. The bill is fairly short, pointed and black; the eye is dark. Juveniles resemble the female, but are finely streaked below.
Confusion species
Bronzed Cowbird Molothrus aeneus is bulkier, with a red eye, a bronzy gloss and, in the male, a ruff on the nape. Screaming Cowbird Molothrus rufoaxillaris has a shorter, thicker bill and a bluer gloss. Giant Cowbird Molothrus oryzivorus is much larger, with a small head and a long tail. Females can be confused with Greyish Baywing Agelaioides badius, which has rufous wings. Great-tailed Grackle Quiscalus mexicanus is much larger, with a long, keeled tail and a yellow eye.
Habitat
Open and semi-open country: pastures, fields, rice paddies, scrub, forest edges, parks and villages, from the coast to about 2500 m and locally higher. It forages in flocks on the ground for seeds and insects, often near cattle. It builds no nest; the female lays her eggs in the nests of many other songbirds, such as Rufous-collared Sparrow Zonotrichia capensis.
Where the bird is most at home, classified by the vegetation units of the Andes and the west coast.
Range and movements
In Colombia in the lowlands on both sides of the Andes and in the Andean valleys. In Ecuador in the western lowlands, the Andean valleys and the eastern lowlands. In Peru along the coast, in the Andean valleys and in the Amazonian lowlands. In Bolivia widespread in the lowlands and valleys. Not established on the Galápagos. Outside the guide area from Panama and the Caribbean to Argentina and Chile.
- Resident
- dark = core range, pale = thinly spread
How and when to look
Look near cattle in pastures and along rice fields; flocks of males and females forage together on the ground and fly up together to a tree or wire.
Conservation status
Least Concern. The species benefits from deforestation and agriculture; through brood parasitism it can locally reduce the breeding success of rare host species.
Scientific name
Molothrus bonariensis | (Gmelin, 1789)
Gmelin described the species in 1789 as Tanagra bonariensis; because it was later moved to another genus, the author and year stand in brackets. The genus Molothrus was introduced in 1832 by Swainson. The genus name comes from Greek mōlos, 'struggle', and thrōskō, 'to impregnate', referring to the brood parasitism of cowbirds. The species name refers to Buenos Aires in Argentina. The specimen the first description was based on came from Buenos Aires, Argentina.