Northern bobwhite quail (Colinus virginianus L.) populations are declining throughout their range. One factor contributing to the decline in the southeastern United States may be the red imported fire ant (Solenopsis invicta Buren). Recent research in Texas has documented that red imported fire ants can have a significant impact on northern bobwhite quail. That research was conducted in areas where fire ants are predominately polygynous (multiple queen). Polygynous infestations have much higher mound densities than the monogynous (single queen) form. In most of the southeastern United States, fire ants are predominately monogynous. We determined if there was a relationship between the invasion of monogynous red imported fire ants and abundance trends in northern bobwhite quail in the southeastern United States. For Florida, Georgia, and South Carolina we compared average northern bobwhite quail abundance based on Christmas Bird Count data for each county before and after fire ant invasion, and conducted regression analyses on bobwhite quail abundance and year preinvasion, and abundance and year postinvasion. Regionally, northern bobwhite quail were more abundant before (0.067 ??0.018 bobwhite quail per observer hour) than after fire ants invaded (0.019 ?? 0.006; Z = -3.746, df = 18, P < 0.001). There was no significant regional population trend for northern bobwhite quail (r2 = 0.24; df = 9, P = 0.13) before fire ant invasion. Post-invasion, northern bobwhite quail populations significantly declined regionally (r2 = 0.76, df = 15, P < 0.001), and in Florida (r2 = 0.71, df = 15, P < 0.01) and South Carolina (r* = 0.50, df = 9, P = 0.01). The number of years that a county had been infested by fire ants explained 75% of the yearly variation in northern bobwhite quail abundance after invasion, despite >30-yr variation in invasion dates.