Brown-headed CowbirdMolothrus ater

adult male
Rick and Nora Bowers/VIREO
adult female
Rick and Nora Bowers/VIREO
juvenile
Rick and Nora Bowers/VIREO
adult male
Rob & Ann Simpson/VIREO
nest with 3 Veery eggs and 1 cowbird egg
Michael Patrikeev/VIREO
Brown-headed Cowbird
Brown-headed Cowbird

Description

6-8" (15-20 cm). Male black with glossy brown head; female plain gray-brown. Both have a finch-like bill.

Voice

Squeaky gurgle. Call is check or a rattle.

Listen

whistle call variants
whistles, chatter, and flight
male song
female chatter
male song and whistle call
male songs & female chatter (duets)

Habitat

Agricultural land, fields, woodland edges, and suburban areas.

Range

Breeds from British Columbia, central Saskatchewan, central Ontario, Quebec, and Newfoundland southward throughout United States except extreme Southeast and Florida. Winters in central and southern part of breeding range as well as in Florida.

Discussion

Cowbirds are brood parasites and promiscuous; no pair bond exists. In late spring the female cowbird and several suitors move into the woods. The males sit upright on treetops, uttering sharp whistles, while the female searches for nests in which to lay her eggs. Upon choosing a nest, she removes one egg of the host's clutch, and deposits one of her own in its place. Unlike parasitic Old World cuckoos, which lay eggs closely resembling those of a host species, cowbirds lay eggs in the nests of more than 200 other species, most smaller than themselves. Some host species eject the unwanted egg, others lay down a mew nest lining over it, but most rear the young cowbird as one of their own. The young cowbird grows quickly at the expense of the young of the host, pushing them out of the nest or taking most of the food. It has been suggested that cowbirds became parasitic because they followed roving herds of bison and had no time to stop to nest.

Nesting

4 or 5 white eggs, lightly speckled with brown, laid one at a time in the nests of other songbirds.

Similar Species

adult, breeding

European Starling

7 1/2-8 1/2" (19-22 cm). Smaller than a robin. A short-tailed, chunky, iridescent black bird; long pointed bill, yellow in summer and dark in fall and early winter.

adult male, breeding

Rusty Blackbird

9" (23 cm). In spring males are black, with a bluish and greenish iridescence; females are dark gray. In fall they are much more rust-brown, especially head, breast, and back.

adult male

Brewer's Blackbird

8-10" (20-25 cm). Robin-sized. Male is solid black with purplish-blue iridescent head and yellow eyes. Female is gray with dark eyes.

adult male, Eastern

Bronzed Cowbird

8 1/2" (22 cm). Male bronze-black with bluish-black wings and tail. Prominent red eye can be seen at close range. Female similar but duller.

adult male

Shiny Cowbird

7-8" (18-20 cm). Male purplish black glossed with blue above, shining purplish black below. Female grayish brown, paler below. Bill large, conical, and black. Eyes dark.

adult male

Boat-tailed Grackle

Males 16-17" (41-43 cm); females 12-13" (30-33 cm). Tail very long and keel-shaped. Male black, iridescent blue on back and breast; yellow or brown eyes. Female smaller, brown with paler breast.

adult male

Great-tailed Grackle

Male, 16-17" (41-43 cm); female, 12-13" (30-33 cm). Tail very long and keel-shaped. Male black, with iridescent purple on back and breast. Female smaller, brown with a pale breast.

adult male Coastal (Purple)

Common Grackle

12" (30 cm). Jay-sized. Long, wedge-shaped tail displaying a longitudinal ridge or keel when in flight.

Vireo

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