Blackbirds (Icteridae)
Brown-headed Cowbird
Molothrus ater. Seeds and insects taken on the ground.
Blackbirds (Icteridae)Brown-headed CowbirdMolothrus ater
- Scientific name
- Molothrus ater
- Length
- 7.5–8.7 in
- Weight
- 1.3–1.8 oz
- Nest
- Builds no nest — lays eggs in the nests of other species
- Entrance hole
- Does not use nest boxes
- Clutch
- Up to 36 eggs per season, one per host nest
- Incubation
- 10–12 days
- Broods
- —
Identification
- Male glossy black with a chocolate-brown head
- Female plain grey-brown
- Short, thick finch-like bill
Voice
Bubbly gurgling whistles from the male; a harsh chatter from flocks.
Diet and feeding
Seeds and insects taken on the ground.
Brown-headed Cowbirds by state and province
| Region | Status | Nesting |
|---|---|---|
| Alabama | Year-round resident | March–July |
| Alberta | Year-round resident | May–July |
| Arizona | Year-round resident | March–July |
| Arkansas | Year-round resident | April–July |
| British Columbia | Year-round resident | May–July |
| California | Year-round resident | March–July |
| Colorado | Year-round resident | April–July |
| Connecticut | Year-round resident | April–July |
| Delaware | Year-round resident | April–July |
| Florida | Year-round resident | March–July |
| Georgia | Year-round resident | March–July |
| Idaho | Year-round resident | April–July |
| Illinois | Year-round resident | April–July |
| Indiana | Year-round resident | April–July |
| Iowa | Year-round resident | April–July |
| Kansas | Year-round resident | April–July |
| Kentucky | Year-round resident | April–July |
| Louisiana | Year-round resident | March–July |
| Maine | Year-round resident | May–July |
| Manitoba | Year-round resident | May–July |
| Maryland | Year-round resident | April–July |
| Massachusetts | Year-round resident | April–July |
| Michigan | Year-round resident | April–July |
| Minnesota | Year-round resident | May–July |
| Mississippi | Year-round resident | March–July |
| Missouri | Year-round resident | April–July |
| Montana | Year-round resident | May–July |
| Nebraska | Year-round resident | April–July |
| Nevada | Year-round resident | April–July |
| New Brunswick | Year-round resident | May–July |
| New Hampshire | Year-round resident | May–July |
| New Jersey | Year-round resident | April–July |
| New Mexico | Year-round resident | April–July |
| New York | Year-round resident | April–July |
| North Carolina | Year-round resident | April–July |
| North Dakota | Year-round resident | May–July |
| Northwest Territories | Summer breeder | May–July |
| Nova Scotia | Year-round resident | May–July |
| Ohio | Year-round resident | April–July |
| Oklahoma | Year-round resident | April–July |
| Ontario | Year-round resident | May–July |
| Oregon | Year-round resident | April–July |
| Pennsylvania | Year-round resident | April–July |
| Quebec | Year-round resident | May–July |
| Rhode Island | Year-round resident | April–July |
| Saskatchewan | Year-round resident | May–July |
| South Carolina | Year-round resident | March–July |
| South Dakota | Year-round resident | April–July |
| Tennessee | Year-round resident | April–July |
| Texas | Year-round resident | March–July |
| Utah | Year-round resident | April–July |
| Vermont | Year-round resident | May–July |
| Virginia | Year-round resident | April–July |
| Washington | Year-round resident | April–July |
| West Virginia | Year-round resident | April–July |
| Wisconsin | Year-round resident | May–July |
| Wyoming | Year-round resident | May–July |
| Yukon | Summer breeder | May–July |
Frequently asked
What do cowbirds eat?
Seeds and insects taken on the ground. At feeders: millet, cracked corn, mixed seed.
How big is a Brown-headed Cowbird?
7.5–8.7 in long and 1.3–1.8 oz.
Do cowbirds use birdhouses?
No. Builds no nest — lays eggs in the nests of other species.
Sources
- Brown-headed Cowbird — All About Birds, Cornell Lab of Ornithology
- Brown-headed Cowbird life history — Cornell Lab of Ornithology
- Brown-headed Cowbird — Audubon Guide to North American Birds
Timing reflects typical patterns for the region as a whole; local dates vary with elevation and year. Check the linked eBird bar charts for your county.