Global Range: Breeding range extends from southeast Alaska, northern British Columbia, and southern Mackenzie to Newfoundland, and south to central Mexico, southern Texas, Gulf Coast, and southern Florida (AOU 1983, Lowther 1993). Winter range extends from northern California, southern New Mexico, Kansas, Great Lakes region, New England, and Nova Scotia south to southern Baja California, Oaxaca, central Veracruz, Gulf Coast, and southern Florida (AOU 1983, Lowther 1993). This species historically occurred in the Great Plains west of the Mississippi River and often was associated with bison that stirred up insects and uncovered seeds. In the 1700s and 1800s, European settlers fragmented the once unbroken expanse of eastern deciduous forest, leading to cowbird expansion throughout the eastern United States and Canada (Mayfield 1965, 1977). Fragmentation of forests and cowbird expansion occurred more recently in the western United States (Verner and Ritter 1983).