Range Extent CommentsBREEDING: central Iowa, southeastern Minnesota (rarely), southern Wisconsin, southern Michigan, extreme southern Ontario, southern New York, and southern Massachusetts, south to southern Mexico (San Luis Potosi, Hidalgo), southern Texas, Gulf Coast, southern Florida and west to eastern Nebraska (formerly), eastern Kansas, central Oklahoma, west-central Texas, and Coahuila (AOU 1998). NON-BREEDING: central Texas, the Gulf states, and extreme southeastern Virginia (Dismal Swamp) south to Guatemala, Belize, and northwestern Honduras (casually to western Panama); also in Bermuda, Bahamas, Jamaica, Cuba, Cayman Islands, Puerto Rico, and St. John (Hopp et al. 1995, AOU 1998). RESIDENT: Bermuda (subspecies BERMUDIANUS) (Hopp et al. 1995). Casual north to North Dakota, southern Manitoba, southern Minnesota, northern Michigan, southern Quebec, Maine, and Nova Scotia, west to California, Utah, Arizona, Colorado, southern New Mexico, Chihuahua, and south to Costa Rica, Panama, Puerto Rico (including Mona Island) and the Virgin Islands (St. John); sight report for Socorro (Revillagigedo Islands) (AOU 1998).
Threat Impact CommentsPREDATION: Potential predators of nests and fledglings include snakes (e.g. Rat Snakes, ELAPHE OBSOLETA), Blue Jays (CYANOCITTA CRISTATA), mice (PEROMYSCUS sp.), Eastern Chipmunks (TAMIAS STRIATUS), Raccoons (PROCYON LOTOR), Virginia Opossums (DIDELPHIS MARSUPIALIS), and Striped Skunks (MEPHITIS MEPHITIS). Short-tailed Hawks (BUTEO BRACHYURUS) are confirmed predators (Ogden 1974). In Bermuda, fledglings sometimes get entangled in golden-silk spider webs (NEPHILA CLAVIPES; Forbush and May 1939 cited in Hopp et al. 1995). NEST PARASITISM: Observed rates of Brown-headed Cowbird nest parasitism vary from 40% in Louisiana (Goertz 1977), to 48.9% in Virginia (Hopp et al. 1995), to 83% in Illinois (Graber et al. 1985). Parasitized host nests typically fledge only cowbird young (Hopp et al. 1995). OTHER: During migration, large numbers are sometimes killed during severe weather. An estimated 1800 individuals were killed by thunderstorms and a tornado in Louisiana during spring migration (Weidenfeld and Weidenfeld 1995). Migrating individuals are killed by colliding with towers (Crawford 1978, Taylor and Anderson 1973, Taylor and Kershner 1986).