Animalia > Chordata > Aves > Passeriformes > Icteridae > Molothrus > Molothrus ater

Molothrus ater (Brown-headed Cowbird)

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Wikipedia Abstract

The brown-headed cowbird (Molothrus ater) is a small obligate brood parasitic icterid of temperate to subtropical North America. They are permanent residents in the southern parts of their range; northern birds migrate to the southern United States and Mexico in winter, returning to their summer habitat around March or April.
View Wikipedia Record: Molothrus ater


Invasive Species

Molothrus ater is a small blackbird that can be found in almost every habitat, open woodlands, fields and marginal habitats in between. It is commonly associated with agriculture (cattle pastures, feed lots) and is migratory, spending time year-round in the southern United States, but occurring only during the breeding season in the northern and mountainous regions of the United States. Molothrus ater has undergone a rapid range expansion with habitat alterations, due to forest clearing, domestic cattle grazing, urbanisation and conversion of forested habitats to agricultural land.
View ISSG Record: Molothrus ater

EDGE Analysis

Uniqueness Scale: Similiar (0) 
 Unique (100)
Uniqueness & Vulnerability Scale: Similiar & Secure (0) 
 Unique & Vulnerable (100)
ED Score: 2.46419
EDGE Score: 1.24248


Adult Weight [1]  43 grams
Birth Weight [3]  2 grams
Female Weight [1]  38 grams
Male Weight [1]  49 grams
Weight Dimorphism [1]  28.9 %
Breeding Habitat [2]  Generalist, Agricultural
Wintering Geography [2]  Southern U.S./Mexico
Wintering Habitat [2]  Generalist, Agricultural
Diet [4]  Carnivore (Invertebrates), Granivore
Diet - Invertibrates [4]  40 %
Diet - Seeds [4]  60 %
Forages - Mid-High [4]  10 %
Forages - Understory [4]  10 %
Forages - Ground [4]  80 %
Female Maturity [3]  1 year
Male Maturity [3]  1 year
Clutches / Year [3]  1
Global Population (2017 est.) [2]  130,000,000
Incubation [3]  11 days
Maximum Longevity [3]  17 years


Protected Areas

+ Click for partial list (100)Full list (281)


Biodiversity Hotspots

Name Location Endemic Species Website
California Floristic Province Mexico, United States No
Caribbean Islands Anguilla, Antigua and Barbuda, Aruba, Bahamas, Barbados, Cayman Islands, Cuba, Dominica, Dominican Republic, Haiti, Grenada, Guadeloupe, Jamaica, Martinique, Montserrat, Netherlands Antilles, Puerto Rico, Saint Kitts and Nevis, Saint Lucia, Saint Vincent And The Grenadines, Trinidad and Tobago, Turks And Caicos Islands, Virgin Islands - British, Virgin Islands - U.S. No
Madrean Pine-Oak Woodlands Mexico, United States No
Mesoamerica Belize, Costa Rica, El Salvador, Guatemala, Honduras, Mexico, Nicaragua, Panama No

Prey / Diet

Prey / Diet Overlap




Parasitized by 
Cardiofilaria pavlovskyi <Unverified Name>[7]
Ceratophyllus diffinis[8]
Porrocaecum ensicaudatum[7]

Institutions (Zoos, etc.)

Institution Infraspecies / Breed 
Columbus Zoo and Aquarium

Range Map


North America; Western Michigan University’s Asylum Lake;

External References


Play / PauseVolume
Provided by Birds Of A Feather on Myxer



Attributes / relations provided by
1Mulvihill, R. S., Leberman, R. C. & Leppold, A. J. Relationships among body mass, fat, wing length, age and sex for 170 species of birds banded at Powdermill Nature Reserve. (Eastern Bird Banding Association Monograph no.1) Hellertown, PA: Eastern Bird Banding Association, 2004, 184 p.
2Partners in Flight Avian Conservation Assessment Database, version 2017. Accessed on January 2018.
3de Magalhaes, J. P., and Costa, J. (2009) A database of vertebrate longevity records and their relation to other life-history traits. Journal of Evolutionary Biology 22(8):1770-1774
4Hamish Wilman, Jonathan Belmaker, Jennifer Simpson, Carolina de la Rosa, Marcelo M. Rivadeneira, and Walter Jetz. 2014. EltonTraits 1.0: Species-level foraging attributes of the world's birds and mammals. Ecology 95:2027
5Study of Northern Virginia Ecology
6Jorrit H. Poelen, James D. Simons and Chris J. Mungall. (2014). Global Biotic Interactions: An open infrastructure to share and analyze species-interaction datasets. Ecological Informatics.
7Gibson, D. I., Bray, R. A., & Harris, E. A. (Compilers) (2005). Host-Parasite Database of the Natural History Museum, London
8International Flea Database
Ecoregions provided by World Wide Fund For Nature (WWF). WildFinder: Online database of species distributions, ver. 01.06 WWF WildFINDER
Biodiversity Hotspots provided by Critical Ecosystem Partnership Fund
Abstract provided by DBpedia licensed under a Creative Commons License
Audio software provided by SoundManager 2