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Shiny Cowbird

Molothrus bonariensis ORDER: PASSERIFORMES FAMILY: ICTERIDAE

IUCN Conservation Status: Least Concern

A common bird throughout much of South America, the Shiny Cowbird only recently spread through the Caribbean and into the United States. A nest parasite like other cowbirds, its spread has imperiled a number of endangered bird species in the Caribbean and raised conservation concerns in the United States.

At a GlanceHelp

Measurements
Both Sexes
Length
7.1 in
18 cm
Weight
1.1–1.4 oz
31–40 g
Other Names
  • Vacher luisant (French)
  • Tordo renegrido, Tordo vaquero, Tordo lustroso (Spanish)

Cool Facts

  • The Shiny Cowbird first reached the United States in 1985 when a single male was seen in the Florida Keys. By the early 1990s they were considered permanent residents in southern Florida. In the next few years individual Shiny Cowbirds were seen as far away as Maine and Nova Scotia.
  • The Shiny Cowbird began expanding its range out of South America around 1900. Its spread was assisted by the removal of natural forest cover on Caribbean islands.
  • The Shiny Cowbird is a widespread species in South America, and seven different subspecies have been described. The northern form, the one that made it to Florida, is the smallest.

Habitat


Grassland

Open or semiopen habitats, especially agricultural areas with patches of trees and shrubs. Suburbs, lawns, and at bird feeders.

Food


Insects

Insects, spiders, and grain.

Nesting

Nesting Facts
Egg Description
White or pale gray. May be marked with brownish spots.
Condition at Hatching
Helpless with sparse pale gray down.
Nest Description

None. Lays eggs in nests of other bird species.

Nest Placement

Tree

Behavior


Ground Forager

Forages while walking on ground, scratches ground with one foot, feeds in trees, or with large animals. Often feeds in mixed flocks of other blackbirds.

Conservation

status via IUCN

Least Concern

Shiny Cowbird's range is expanding. Partners in Flight estimates a global breeding population of 200 million, with almost all birds living in South America, though Shiny Cowbird have been recorded in Southeastern states and along the East Coast and Gulf of Mexico in the U.S. They rate a 4 out of 20 on the Continental Concern Score and are not on the 2014 State of the Birds Watch List. Though there are no immediate conservation concerns about Shiny Cowbird, there is concern about the effect expanding ranges that these cowbirds may have on their hosts. Parasitism by Shiny Cowbirds may have caused declines in endangered Yellow-shouldered Blackbird and Puerto Rican Vireo populations in Puerto Rico.

Credits

Range Map Help

Shiny Cowbird Range Map
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bird image Blue-winged Warbler by Brian Sullivan

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