Differential influence of weather on regional quail abundance in Texas

Although weather variables are known to influence quail abundance in some habitats, most studies have addressed only limited geographic areas and indices to weather conditions. The few replicated studies addressed relatively similar climate zones. We used 21 years (1978-98) of quail abundance data collected by the Texas Parks and Wildlife Department (TPWD) biologists to address the relationship between both simple precipitation and Palmer drought indices and Northern Bobwhite (Colinus virginianus) and Scaled quail (Callipepla squamata) abundance in 6 ecological regions of Texas. Three 12-month Palmer indices were more highly correlated with changes in Northern Bobwhite abundance in the South Texas Plains ecological region than was raw precipitation alone. The 12-month Modified Palmer Drought Severity Index (PMDI) was correlated (r(s) greater than or equal to 0.78, P less than or equal to 0.001) with the mean number of Northern Bobwhites visually observed per sun ey route in the Rolling and South Texas Plains ecological regions, while a le-month, raw precipitation index was correlated (r(s) = 0.64, P = 0.002) with Northern Bobwhite abundance in only the South Texas Plains. The PMDI and raw precipitation were correlated (r(s) greater than or equal to 0.67, P less than or equal to 0.001and r(s) greater than or equal to 0.57, P less than or equal to 0.007, respectively) with the mean number Scaled Quail observed per survey route in the Edwards Plateau, South Texas Plains, and Trans-Pecos Mountains and Basins ecological regions. There was no relationship (P greater than or equal to 0.437) between changes in quail abundance and the PMDI or raw precipitation in the Gulf Prairies and Marshes physiographic region, where precipitation was relatively high. The monthly PMDI was a better indicator of changes in both northern bobwhite and Scaled Quail abundance among years than was monthly precipitation alone. Both monthly and 12-month precipitation-based weather indices were more correlated with changes in Northern Bobwhite and scaled quail abundance among years in relatively dry as opposed to wet ecological regions. Our approach should help wildlife biologists and managers better account for annual variability in quail productivity in semi-arid environments so that long-term populations trends can be better elucidated.