Shiny Cowbird Molothrus bonariensis - some photos and notes

Shiny Cowbird Molothrus bonariensis

Shiny Cowbird, Rio Grande do Sul, Brazil, August 2004 - click for larger image

The Shiny Cowbird was originally found only in South America where it is widespread in most habitats except forest and mountains. However, it has been spreading northwards through Central America and island hopping across the Caribbean. It reached the Florida Keys in 1985, mainland Florida in 1987 and is now found in several states of the US. See the distribution map at xeno-canto.

The male is shiny purplish black while the female, seen in the middle of the second photo is dull browny-grey.

It is a brood parasite and, according to Jaramillo & Burke it has been reported as having parasitised 201 species of which 53 successfully. It lays one egg in the host nest from which it removes one of the host's eggs. It also outcompetes the other nestlings bringing further grief to the host species.

Male Shiny Cowbird, Laguna de Laja N. P., Chile, November 2005 - click for larger image

It derives its name from the habit of foraging near cattle and often feeding on ticks from the cattle's skins.

Photos 5 and 6 from the Cauca Valley, Colombia are of the sub-species M. b. cabanisii while photo 7 from western Ecuador is of M. b. aequatorialis which is the largest and most purple of all the sub-species.

Female or Juvenile Shiny Cowbird, Laguna de Laja N. P., Chile, November 2005 - click for larger image

Male Shiny Cowbird, Los Cerritos, Risaralda, Colombia, April 2012 - click for larger image

Male Shiny Cowbird, Rio Silanche, Pichincha, Ecuador, November 2019 - click for larger image

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