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Bronzed Cowbird

Molothrus aeneus ORDER: PASSERIFORMES FAMILY: ICTERIDAE

IUCN Conservation Status: Least Concern

A Central American bird, the Bronzed Cowbird makes its way to the United States only in the border states and Louisiana. Like other cowbirds, the female does not make a nest, but instead lays her eggs in the nests of other bird species.

At a GlanceHelp

Measurements
Both Sexes
Length
7.9 in
20 cm
Wingspan
13 in
33 cm
Weight
1.9–2.5 oz
55–70 g
Other Names
  • Red-eyed Cowbird
  • Vacher bronze (French)
  • Tordo ojirojo (Spanish)

Cool Facts

  • Nest success for brood parasites (birds that lay eggs in the nests of other bird species) usually is best when only one parasite egg is laid in a given nest. Host nests frequently contain multiple Bronzed Cowbird eggs. Some female cowbirds peck the other cowbird eggs before laying their own eggs, effectively reducing the number of cowbird eggs in the nest.
  • The maximum number of Bronzed Cowbird eggs found in one nest was 14 in an abandoned nest.
  • The oldest recorded Bronzed Cowbird was a male, and at least 8 years old when he was found in Texas.

Habitat


Town

Open fields, pastures, scrubby areas, tropical semideciduous forest, tropical deciduous forest, tropical scrub, lawns, golf courses, and agricultural areas.

Food


Insects

Seeds and arthropods.

Nesting

Nesting Facts
Egg Description
Unmarked bluish green.
Condition at Hatching
Helpless with sparse gray down.
Nest Description

None. Lays eggs in nests of other bird species.

Nest Placement

Tree

Behavior


Ground Forager

Forages as it walks on ground; rarely in vegetation, frequently in association with cattle; forages in flocks, often with other blackbirds.

Conservation

status via IUCN

Least Concern

Populations of bronzed Cowbird are stable, but may have declined slightly between 1966 and 2014, according to the North American Breeding Bird Survey. Partners in Flight estimates a global breeding population of 9 million with 10% breeding in the U.S., and 73% spending part of the year in Mexico. They rate a 6 out of 20 on the Continental Concern Score and are not on the 2014 State of the Birds Watch List. Settlement of North America by Europeans has undoubtedly permitted expansion by Bronzed Cowbird into areas converted into agricultural habitats. Management concerns are more likely for host species than for the cowbird. Bronzed Cowbird parasitism has been assumed to be a factor (along with habitat loss) responsible for decreasing populations of Altamira Orioles and Audubon's Orioles in southern Texas.

Credits

Range Map Help

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

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