Bronzed Cowbird

Bronzed Cowbird, adult male; S. Padre, TX

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1. Cool Facts
2. Description
3. Similar Species
4. Sound
5. Range
6. Habitat
7. Food
8. Behavior
9. Reproduction
10. Conservation Status
11. Other Names

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.

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.

Description

• Size: 20 cm (8 in)
• Wingspan: 33 cm (13 in)
• Weight: 55-70 g (1.94-2.47 ounces)

• Medium-sized songbird.
• Medium-long tail.
• Bill stout and pointed.
• Male shiny black with red eyes.
• Female dull gray-brown.

• Male with conspicuous ruff that can be erected on back and sides of neck.

Sex Differences

Male all black, female grayish brown.

Male

Blackish overall. Bronzy iridescence on back and rump. Can erect ruff of feathers on neck. Bill black. Eyes red in breeding season, brownish orange in nonbreeding season. Legs black.

Female

Overall dull black or grayish brown. Lacks ruff. Eyes brownish orange.

Immature

Similar to female, with indistinct dark streaks on breast and belly.

Similar Species

• Brown-headed Cowbird is smaller, has shorter bill, smaller head, longer tail, and dark brown eyes. Male has brown hood contrasting with black body.
• Shiny Cowbird has thinner bill, and lacks red eyes and neck ruff.
• Brewer's Blackbird female darker brown, has dark around the eyes, and has a thinner, more pointed bill.

Sound

Song short gurgling whistles. Call a harsh "chuck."

Range

Range Map

© 2004 Cornell Lab of Ornithology

About the map

Summer Range

Breeds from very southern California to Louisiana, southward to northern South America.

Winter Range

Winters from very southern United States to South America.

Habitat

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

Food

Seeds and arthropods.

Behavior

Foraging

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

Reproduction

Nest Type

None. Lays eggs in nests of other bird species.

Egg Description

Unmarked bluish green.

Condition at Hatching

Helpless with sparse gray down.

Conservation Status

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.

Other Names

Vacher bronze (French)
Tordo ojirojo (Spanish)
Red-eyed Cowbird (English)

Sources used to construct this page:

Lowther, P. E. 1995. Bronzed Cowbird (Molothrus aeneus). In The Birds of North America, No. 144 (A. Poole and F. Gill, eds.). The Academy of Natural Sciences, Philadelphia, and The American Ornithologists? Union, Washington, D.C.