• Welcome to BirdForum, the internet's largest birding community with thousands of members from all over the world. The forums are dedicated to wild birds, birding, binoculars and equipment and all that goes with it.

    Please register for an account to take part in the discussions in the forum, post your pictures in the gallery and more.
Feel the intensity, not your equipment. Maximum image quality. Minimum weight. The new ZEISS SFL, up to 30% less weight than comparable competitors.

Shiny Cowbird - BirdForum Opus

Stub.png This article is incomplete.
This article is missing one or more sections. You can help the BirdForum Opus by expanding it.

Photo © by Steve G
Asa Wright Centre, Trinidad.
(Picture shows a bird much bluer than I have ever seen, possibly due to special light effects; use the gallery link below to see the variation in this species)
Molothrus bonariensis


Photo © by njlarsen
Congo Rd Shooting Swamp, Barbados
5 January 2013

Male: Shiny black with purple gloss, conical bill (See note under picture)
Female: Grayish brown upperside, lighter brown underside with slight spotting, faint supercilium
Eyes dark brown.

Similar Species

Photo © by Rodrigo Reyes
Via del Mar, Chile, 9 November 2005

Carib Grackle differs in having pale eye, longer bill, and keel-shaped tail, where tail of Shiny Cowbird is flat


Found from south east USA through the Caribbean and South America to Argentina. The spread north from South America started around 1900 and is still ongoing.

Strangely, the species initially did not become established in or completely circumvented some of the islands in the Lesser Antilles including e.g., Dominica, where it is only now starting to appear in numbers (2011-2012).



There are 7 subspecies[1]:

  • M. b. minimus

L Antilles (n to Martinique), Trinidad, Tobago, Guianas, n Brazil

  • M. b. cabanisii

Eastern Panama (Darien) to Colombia

  • M. b. venezuelensis

Tropical eastern Colombia and northern Venezuela

  • M. b. aequatorialis

Tropical southwestern Colombia to westrn Ecuador and Isla Puna

  • M. b. occidentalis

Extreme southwestern Ecuador (Loja) and w Peru (south to Lima)

  • M. b. riparius

Tropical eastern Peru (Río Ucayali) to lower Amazon Valley (Para)

  • M. b. bonariensis

Eastern Bolivia to Paraguay, Brazil, Uruguay and central Argentina


Favours open areas, mostly at lower elevations (at least in the Caribbean)



This species engages in nest parasitism where the female lays its eggs in the nest of other birds, with 250 different species known to have had eggs placed in their nest and almost 100 of these known to have raised young of Shiny Cowbird. In the Caribbean, there seems to be a preference for members of the icterids such as orioles and blackbirds, but in southern South America many different groups of birds are among the known hosts. Shiny Cowbird has caused a decline in several species, and is one of the reasons that the Yellow-shouldered Blackbird is endangered. During egg laying, it is common that Shiny Cowbird puncture or remove at least one host-species egg from the nest.


  1. Clements, J. F., T. S. Schulenberg, M. J. Iliff, S. M. Billerman, T. A. Fredericks, B. L. Sullivan, and C. L. Wood. 2019. The eBird/Clements Checklist of Birds of the World: v2019. Downloaded from http://www.birds.cornell.edu/clementschecklist/download/
  2. Neotropical Birds Online

Recommended Citation

External Links

GSearch checked for 2020 platform.1