Northern bobwhite chick mortality caused by red imported fire ants

Northern bobwhite (Colinus virginianus) populations have declined throughou t their range during the last 30 years. Change in land management is though t to be a primary cause of this decline, but the invasion of northern bobwh ite habitats by the red imported fire ant (Solenopsis invicta) also may be involved. We compared hatching success and subsequent survival of wild nort hern bobwhite chicks on the Coastal Prairie of Texas in 1997 and 1998 betwe en broods that hatched under natural conditions or following fire ant suppr ession treatments. In 1997, the fire ant suppression treatment resulted in a 70% reduction in the number of red imported fire ants on baits placed in treated nests on the day after hatch. Using 2 fire ant suppression treatmen ts in 1998 reduced the number of red imported fire ants on baits by >99%. N o year or treatment x year interaction effects were detected for hatching s uccess or survival, and no treatment effect was detected for hatching succe ss (P > 0.10). However, the proportion of chicks surviving to 21 days was h igher (P = 0.010) for treated nests (n = 18) than control nests (n = 25; pr oportions of broods surviving: 53.5 +/- 8.6% [(x) over bar +/- SE] vs. 24.7 +/- 6.6%; chick survival: 60.1 +/- 7.6% vs. 22.0 +/- 6.2%). The probabilit y of chick survival decreased (P < 0.001) as our index of red imported fire ant activity in the nest increased. These results indicate northern bobwhi te chicks can suffer high levels of mortality due to red imported fire ants , which could explain declines in some northern bobwhite populations follow ing infestations by red imported fire ants. Current methods for controlling red imported fire ants are expensive and may last <3 months. Thus, strateg ies for mitigating the effect of red imported fire ants to northern bobwhit e populations in this area should probably focus on reducing other mortalit y factors or increasing productivity.