Brown-headed cowbird
Molothrus ater
ITIS Species Code:   179112         NatureServ Element Code:   ABPBXB7030
NatureServe Global Rank: 
NatureServe State (NC) Rank: 
Federal Status: 
NC State Status: 
Southern Blue Ridge:  11 Southern Piedmont:  13 South Atl. Coastal Plain:  10
Land Unit

US Fish & Wildlife Service
US Forest Service
US National Park Service
US Department of Defense
NC State Parks
NC University System
NC Wildlife Res. Com.
NC Forest Service
NC Div. of Coastal Mgmt.
Local Governments
Non-Governmental Org.
Other Public Lands
Private Lands

GAP Status 1-2
All Protected Lands




% of Dist. on
Prot. Lands

12.2 %
37.7 %
15.1 %
6.9 %
5.2 %
4.0 %
12.9 %
1.8 %
0.9 %
2.0 %
2.0 %
0.5 %
< 0.1 %

39.2 %
% of Dist. on
All Lands

1.0 %
3.1 %
1.3 %
0.6 %
0.4 %
0.3 %
1.1 %
0.2 %
< 0.1 %
< 0.1 %
0.2 %
< 0.1 %
91.8 %

3.2 %
Uncommon to common throughout the state (Potter et al. 1980).

Require short grass for foraging, and the presence of other nesting songbirds (Nicholson 1997). Commonly inhabit wooded areas, agricultural lands, residential areas (Fussell 1994), and especially forest edges (Simpson 1992).

Do not build a nest or care for young; instead, lay eggs in the nests of various other species. Primarily forage for seeds on the ground with conspecifics and flocks of other blackbirds, but will eat fruit, and also insects attracted to livestock (Skutch 1996).


BREEDING: Woodland, forest (primarily deciduous), forest edge, city parks, suburban gardens, farms, ranches. Before European settlement of the eastern U.S., cowbirds were apparently limited to the open grasslands of the United States, mostly west of the Mississippi River. However, because the cowbirds need suitable perches for searching for nests to parasitize, the species was probably limited in the breeding season to prairie riparian corridors (Mayfield 1965).

The main reason for cowbird expansion outside of the Great Plains appears to be the fragmentation of once unbroken forest tracts into small pieces of forest interspersed with fields, pastures, roads, and towns (Mayfield 1977b, Kerlinger and Doremus 1981). Cowbirds often are associated with forest-field edge habitat and clearings in forests.

Feedlots, pastures, and fields with livestock also attract cowbirds, especially in predominately forested areas. In the Sierra Nevada of California, cowbirds feed in horse corrals, meadows with herds of cattle, and at bird feeders in towns, and few cowbirds are found more than 10 km from these food sources (Verner and Ritter 1983). In this same area, the number of cowbirds in meadows decreases as the distance of the meadow from pack stations and horse corrals increases.

NON-BREEDING: In migration and winter, occurs also in open situations, cultivated lands, fields, pastures, and scrub.

Occupied Landcover Map Units:
Code NameDescription NC Natural Heritage Program Equivalent
124 Maritime Scrubs and Tidal Shrublands Coastal shrubs including wax-myrtle, swamp rose, alder, yaupon, and greenbriar. Maritime Shrubs, Salt Shrub
371 Maritime Grasslands Dune grass community consisting of sea oats and beach grasses. Dune grass, Maritime dry grassland
121 Maritime Pinelands Loblolly forests and woodlands of the outer coastal plain. Estuarine Fringe Loblolly Pine Forest
17 Maritime Forests and Hammocks Maritime forests and woodlands dominated by live or sand laurel oak. Estuarine Fringe forests dominated by loblolly pine. Coastal Fringe Evergreen Forest, Maritime Deciduous Forest, Maritime Deciduous Forest
173 Coastal Plain Riverbank Shrubs Shrub dominated riverbanks, commonly dominated by willows and/or alders. Sand and Mud Bar
158 Coastal Plain Nonriverine Wet Flat Forests Loblolly pine - Atlantic white-cedar - red maple - swamp tupelo saturated forests as well as forests dominated by loblolly, sweetgum, and red maple in non-riverine flats. Non-riverine Wet Hardwood Forest
41 Peatland Atlantic White-Cedar Forest Dense stands of Atlantic white cedar with saturated hydrology. Can include swamp tupelo, red maple, and pond pines with a moderate shrub and herb layer. Peatland Atlantic White-Cedar Forest
15 Seepage and Streamhead Swamps Includes extensive peat flats in the coastal plain, dominated by swamp tupelo, maples, and Atlantic white cedar alliances. In the sandhills includes streamhead pond pine and bay forests alliances. Saturated hydrology. Bay Forest, Small Depression Pocosin, Streamhead Atlantic White Cedar Forest, Streamhead Pocosins
63 Coastal Plain Mesic Hardwood Forests Beech dominated forests with white oak and northern red oak as possible co-dominants. Dry-mesic to mesic forests on slopes and small stream bottoms in the coastal plain. Mesic Mixed Hardwood Forest, Basic Mesic Forests
138 Coastal Plain Dry to Dry-Mesic Oak Forests Oak dominated forests of the coastal plain. Includes white oak forests with water oak or northern red oak and hickories as co-dominants. Dry Mesic Oak Hickory Forest, Basic Oak Hickory Forest, Dry Oak Hickory Forest
87 Pocosin Woodlands and Shrublands Includes pond pine woodland, low pocosin and high pocosin shrub dominated areas. Canebrakes and bay forests may be present. Pond Pine Woodlands, Peatland Canebrake, Small Depression Pocosin
67 Wet Longleaf or Slash Pine Savanna Wet flatwoods and pine savannas, typically dominated by longleaf pines, but slash or pond pines may be the dominant pines. Wet Pine Flatwoods
97 Mesic Longleaf Pine Longleaf pine woodlands without a major scrub oak component. Slash or loblolly pines may be present as well. Mesic Pine Flatwoods
42 Xeric Longleaf Pine Sandhills including a range of longleaf pine density from predominantly wiregrass, scrub oak dominated to true longleaf pine woodland. This does not include mesic or saturated flatwood types. Xeric Sandhill Scrub, Pine/Scrub Oak Sandhill, Coastal Fringe Sandhill
46 Xeric Oak - Pine Forests Mixed forest dominated by yellow pines with white or northern red oaks co-dominating. Pine Oak Heath
232 Xeric Pine-Hardwood Woodlands and Forests Mixed forest dominated by yellow pines with drier oaks including southern red, post, and chestnut oaks. Dry Oak Hickory Forest
239 Piedmont/Mountain Emergent Vegetation Emergent vegetation of all wetland hydrologies. Sites would commonly support species such as tussock sedge, rushs, and cattail alliances. Rocky Bar and Shore (in part)
267 Riverbank Shrublands Riverside shrubs with temporarily flooded hydrologies. Found in the both the Mountains and Piedmont. Containing dominants such as smooth alder and a Carolina or black willows. Sand and Mud Bar
269 Floodplain Wet Shrublands Saturated shrublands of the Piedmont, includes buttonbush, swamp-loosestrife, decodon and alders. Piedmont/mountain Semipermanent Impoundment
230 Piedmont Mesic Forest American Beech - Red Oak - White Oak Forests. Mesic Mixed Hardwood
383 Piedmont Mixed Successional Forest Generally loblolly mixed with successional hardwoods. Sweetgum, tulip poplar and red maple are common co-dominants in these successional forests. No equivalent
228 Piedmont Dry-Mesic Oak and Hardwood Forests Primarily oak dominated forests, white oak is often dominant, with co-dominants including . Also represented by sweetgum and tulip poplar dominated forests. Dry Mesic Oak Hickory Forest, Basic Oak Hickory Forest, Dry Oak Hickory Forest
222 Piedmont Dry-Mesic Pine Forests Loblolly dominated forests resulting from succession following clearing. This type occurs on all moisture regimes following disturbance with the exception of the extremely xeric sites. No equivalent
382 Dry Mesic Oak Pine Forests Mixed forests of the coastal plain and piedmont. Includes loblolly pine with white, southern red and/or post oak and loblolly with water oak. On basic sites of the piedmont, eastern red cedar may co-occur with post, black, and blackjack oaks. Dry Mesic Oak Hickory Forest, Xeric Hard Pan Forest, Chestnut Oak Forest, Dry Mesic Oak Hickory Forest, Dry Oak Hickory Forest
220 Piedmont Xeric Pine Forests Dry to xeric pine forests dominated by Virginia pine, shortleaf pine or Eastern Red Cedar. Pine Oak Heath
226 Piedmont Xeric Woodlands Generally post and blackjack oak dominated woodlands. White ash and pignut hickory can be found in combination with Eastern red cedar on glades. Xeric Hardpan Forest
20 Coniferous Regeneration Regenerating pine stands. Predominantly loblolly pine, but slash and longleaf stands occur as well. No equivalent
21 Coniferous Cultivated Plantation (natural / planted) Managed pine plantations, densely planted. Most planted stands are loblolly, but slash and longleaf occur as well. No equivalent
51 Deciduous Cultivated Plantation Planted deciduous trees. Includes sweetgum and sycamore plantations. No equivalent
36 Successional Deciduous Forests Regenerating deciduous trees with a shrub stature. Commonly dominated by sweetgum, tulip poplars and maples. No equivalent
180 Agricultural Crop Fields Farm fields used for row crops. No equivalent
205 Agricultural Pasture/Hay and Natural Herbaceous Farm fields used for pasture grass or hay production, as well as old fields dominated by native and exotic grasses. No equivalent
202 Residential Urban Includes vegetation interspersed in residential areas. Includes lawns, mixed species woodlots, and horticultural shrubs. Vegetation accounts for between 20 - 70% of the cover. No equivalent
522 Northern Hardwoods High Elevation forests including yellow birch, American beech, and yellow buckeye. Includes forests with Hemlock and Yellow Birch. Northern Hardwoods Forest, Boulderfield Forest
525 Appalachian Oak Forest A variety of oak forest types including Black, White, Scarlet Oaks in dry to mesic situations. Includes forests historically co-dominated by American Chestnut. High Elevation Red Oak Forest, Montane White Oak Forest
526 Appalachian Cove Forest Mixed Mesophytic forests of the mountains. Includes tuliptree, basswood, yellow buckeye and surgar maple. This class is mapped to include cove forests dominated or co-dominated by hemlock. Rich Cove Forest, Acidic Cove Forest
530 Appalachian Xeric Deciduous Forest Deciduous forests in the mountains dominated by Xeric Oak species. Species include, white, Southern red, black, and rock chestnut. High Elevation Red Oak Forest, Montane White Oak Forest
View Entire Landcover Legend
Additional Spatial Constraints:
Exclude all area outside of known range.
Limited to elevation range: less than 3500 ft.
Mayfield, H.F. 1977. Brown-headed Cowbird:agent of extermination. American Birds 31:107-113.

Kerlinger, P., and C. Doremus. 1981. Habitat disturbance and the decline of dominant avian species in pine barrens of the northeastern United States. American Birds 35:16-20.

Trail, P. W., and L. F. Baptista. 1993. The impact of brown-headed cowbird parasitism on populations of the Nuttall's white-crowned sparrow. Conservation Biology 7:309-.

Thompson, F.R., III. 1994. Temporal and spatial patterns of breeding Brown-headed Cowbirds in the midwestern United States. Auk 111:979-990.

Friedmann, H. 1929. The cowbirds:a study in the biology of social parasitism. Charles C. Thomas, Publisher, Springfield, Illinois.

Simpson MB Jr. 1992. Birds of the Blue Ridge Mountains. Chapel Hill and London: University of North Carolina Press.

Fussell, J.O. III. 1994. A birderís guide to coastal North Carolina. Chapel Hill and London: The University of North Carolina Press.

Nicholson CP. 1997. Atlas of the breeding birds of Tennessee. Knoxville: University of Tennessee Press.

Weatherhead, P. J. 1989. Sex ratios, host-specific reproductive success, and impact of brown-headed cowbirds. Auk 106:358-366.

Bent, A.C. 1958. Life histories of North American blackbirds, orioles, tanagers, and their allies. U.S. National Museum Bulletin 211. Washington, DC.

Scott, D. M., and C. D. Ankney. 1983. The laying cycle of brown-headed cowbirds:passerine chickens? Auk 100:583-592.

Verner, J., and L.V. Ritter. 1983. Current status of the Brown-headed Cowbird in the Sierra National Forest. Auk 100:355-368.

Woodward, P.W. 1983. Behavioral ecology of fledgling Brown-headed Cowbirds and their hosts. Condor 85:151-163.

Mayfield, H.F. 1965. The Brown-headed Cowbird, with old and new hosts. Living Bird 4:13-28.

Harrison, C. 1978. A field guide to the nests, eggs and nestlings of North American birds. Collins, Cleveland, Ohio.

Harrison, H.H. 1979. A field guide to western birds' nests. Houghton Mifflin Company, Boston. 279 pp.

Potter, E. F., J. F. Parnell, and R. P. Teulings. 1980. Birds of the Carolinas. Univ. North Carolina Press, Chapel Hill. 408 pp.

Terres, J.K. 1980. The Audubon Society encyclopedia of North American birds. Alfred A. Knopf, New York.

American Ornithologists' Union (AOU), Committee on Classification and Nomenclature. 1983. Check-list of North American Birds. Sixth Edition. American Ornithologists' Union, Allen Press, Inc., Lawrence, Kansas.

Friedmann, H., and L.F. Kiff. 1985. The parasitic cowbirds and their hosts. Proceedings Western Foundation of Vertebrate Zoology 2(4). 78 pp.

Fleischer, R.C., S.I. Rothstein, and L.S. Miller. 1991. Mitochondrial DNA variation indicates gene flow across a zone of known secondary contact between two subspecies of the brown-headed cowbird. Condor 93:185-189.

Glahn, J.F., et al. 1991. Impact of roost control on local urban and agricultural blackbird problems. Wildlife Society Bulletin 19:511-522.

Ball, R. M., Jr., and J. C. Avise. 1992. Mitochondrial DNA phylogenetic differentiation among avian populations and the evolutionary significance of subspecies. Auk 109:626-636.

10 March 2005
This data was compiled and/or developed by the North Carolina GAP Analysis Project.

For more information please contact them at:
NC-GAP Analysis Project
Dept. of Zoology, NCSU
Campus Box 7617
Raleigh, NC 27695-7617
(919) 513-2853