Use of Extinguish PlusTM to Reduce Red Imported Fire Ants and Increase Northern Bobwhite Abundance
Authors: James Caldwell
Populations of northern bobwhite (Colinus virginianus) have been declining throughout Texas since at least the 1970s. The red imported fire ant (RIFA, Solenopsis invicta) was introduced to the southern United States from South America around the 1920s and reached Texas by the 1950s. Previous studies have documented the negative effects of RIFA on northern bobwhite populations through both direct predation and indirect reduction of small invertebrates; a major food source for bobwhites.
In 2013 and 2014, large areas of the Attwater Prairie Chicken National Wildlife Refuge (APCNWR) in Colorado County, Texas were aerially treated with Extinguish PlusTM, a chemical pesticide and reproductive inhibitor which targets ants. My study took place on this refuge and my objectives included evaluation of the impacts of (1) RIFA treatment on RIFA abundance, (2) RIFA treatment on invertebrate abundance, (3) RIFA treatment on northern bobwhite nest success, and (4) invertebrate abundance on northern bobwhite brood survival. I trapped, banded, and radio-collared northern bobwhites in areas treated and not treated with Extinguish PlusTM from May 2014 through May 2015. I also collected RIFA and invertebrate abundance data on areas treated and not treated during the 2014 and 2015 northern bobwhite nesting seasons. These data allowed for the assessment of northern bobwhite brood survival, RIFA abundance, and invertebrate abundance across treated and non-treated areas of the refuge. iii
Treatment with Extinguish PlusTM reduced the presence of RIFA on the refuge. However, significantly (P = 0.019) lower mean invertebrate biomass per sample was found in treated areas and no significant (P = 0.219) difference in mean numbers of individuals per sample were found between treated and non-treated areas. Additionally, data collected suggested that non-treated areas had higher bobwhite brood survival than did treated areas.
My data suggest that treatment with Extinguish PlusTM did not increase northern bobwhite abundance on the APCNWR during the 2014 nesting season. My results differ from previous studies and this may be due to time since treatment and differences in environmental factors between treated and non-treated areas. It also is possible that northern bobwhites are adapting to the presence of RIFA.