Family New World Blackbirds (Icteridae)

Least Concern

Brown-headed Cowbird (Molothrus ater)


French: Vacher à tête brune German: Braunkopf-Kuhstärling Spanish: Tordo cabecipardo

Oriolus ater


, 1783,

Carolina, USA


Race obscurus intergrades with artemisiae in Sierra Nevada (California). Proposed race californicus (described from L Buena Vista, Kern County, in SC California) subsumed into obscurus. Three subspecies recognized.

Subspecies and Distribution
  • M. a. obscurus (J. F. Gmelin, 1789) – Pacific seaboard from S Alaska (rare) S (E to the Cascades and Sierra Nevada) to NW & N Mexico (N Baja California, also on mainland S to Oaxaca); N populations migrate to S parts of breeding range, in Mexico extending to S Baja California.
  • M. a. artemisiae Grinnell, 1909 – W Canada (interior British Columbia E to SC Manitoba) S in W USA (E from the Cascades and Sierra Nevada) to California, Nevada and New Mexico; migrates S to Mexico (S to Michoacán).
  • M. a. ater (Boddaert, 1783) – SE Canada (S Ontario E to Newfoundland) S throughout E USA to C Texas, Gulf Coast and C Florida, and in E Mexico S to Tamaulipas; winters in Florida and in Mexico S to Oaxaca.
  • Also breeds in Yukon (NW Canada); race undetermined, possibly artemisiae.

    Descriptive notes

    Male 18–20 cm, female 16–18 cm; male 43·1–57·3 g and female 32·3–42·3 g (nominate), male average 47·5 g and female... read more


    Male song, from perch, consists of two low-pitched warbles (or a series of clicks) followed by thin... read more


    Found in almost all open habitats, such as grasslands, pastures, woodland edge, agricultural fields... read more

    Food and feeding

    Feeds on insects and other arthropods; also on seeds of both wild and cultivated plants. Forages on ground, often around grazing mammals,... read more


    Season mid-Apr to mid-Jul, with some local variations. Mating system variable, from monogamy to promiscuity. A generalized brood parasite,... read more


    Short-distance to medium-distance migrant. W race obscurus migrates S into Baja California... read more

    Status and conservation

    Not globally threatened. Common to locally abundant in most of range. At end of 20th century, estimated global population was 20,000,000–40,000,000 individuals. Before... read more

    Recommended citation

    Fraga, R. & Garcia, E.F.J. (2020). Brown-headed Cowbird (Molothrus ater). In: del Hoyo, J., Elliott, A., Sargatal, J., Christie, D.A. & de Juana, E. (eds.). Handbook of the Birds of the World Alive. Lynx Edicions, Barcelona. (retrieved from on 25 February 2020).