Brown-headed Cowbird
(Molothrus ater)


Picture of bird
© Jukka Jantunen (
For additional photos and vocalizations, visit Dendroica. (Link opens in a new window.)

The Brown-headed Cowbird is an abundant bird of open prairie and agricultural land, with a breeding range that reaches from the west to the east coast of Canada. Results from the Breeding Bird Survey show that populations have decreased significantly at the national level since about 1970. However, in the Prairie Potholes Bird Conservation Region, the core of the species' range in Canada, the population has shown little overall change. As Canada's only true brood parasite, the species has been suspected of harming host species' populations, and has therefore been subjected to control programs, primarily in the United States (Lowther 1993). This species has been identified as a priority for conservation and/or stewardship in one or more Bird Conservation Region Strategies in Canada.


Main designations for the species
DesignationStatusDateSubspecies, population
IUCN (Global)Least concern2018 
Wild Species (Canada)Secure2015 
Bird Conservation Region StrategyPriority Species2013 

Population status

Geographic area or populationPopulation change relative to ~1970ReliabilityStatus in relation to goal
CanadaModerate DecreaseHighAt an Acceptable Level

Population estimate

Geographic area or populationPopulation estimate
Canada5,000,000 - 50,000,000 adults

Distribution maps


Migration strategy, occurrence

Short-distance migrant

Responsibility for conservation

Geographic areaResponsibility based on % of global population

General nesting period in Canada

Nesting period starts between early May and early June and ends between late July and early August, depending on the region. Before or after this period, the probability of an active nest is lower.

Conservation and management

European settlement of North America, with the subsequent opening up of forested areas for agriculture, greatly benefited the Brown-headed Cowbird and facilitated its range expansion eastward (Lowther 1993). In its historical range in the Prairies, the population has remained stable, but elsewhere, populations have decreased substantially. Conservation concern is currently greater for the sensitive host species that it parasitizes in the United States, such as Kirtland's Warbler, Black-capped Vireo, and Least Bell's Vireo. Cowbird control programs have been used in the United States to protect Kirtland's Warbler (Lowther 1993).


Bird conservation region strategies

Environment and Climate Change Canada and partners have developed Bird Conservation Region Strategies in each of Canada’s Bird Conservation Regions (BCRs). In these strategies, selected species are identified as priorities for one or more of the following reasons:

  • conservation concerns (i.e., species vulnerable due to population size, distribution, population trend, abundance, or threats)
  • stewardship responsibilities (i.e., species that typify the regional avifauna or have a large proportion of their range or population in the sub-region)
  • management concerns (i.e., species that require ongoing management because of their socio-economic importance as game species, or because of their impacts on other species or habitats)
  • other concerns (i.e., species deemed a priority by regional experts for other reasons than those listed above or because they are listed as species at risk or concern at the provincial level)

Select any of the sub-regions below to view the BCR strategy for additional details.

BCRs, marine biogeographic units, and sub-regions in which the species is listed as a priority
RegionSub-region and priority type
Atlantic Northern ForestsAtlantic Northern Forests, sub-region and priority type: Atlantic, PE -- Other