Factors Influencing Survival of Radiotagged and Banded Northern Bobwhites in Georgia

Abstract: Numerous studies of behavior and ecology of northern bobwhites (Colinus virginianus) have depended on radiotagging and telemetry for data collection. Excluding the presumably short-term effects of trapping, handling, and attaching radiotransmitters, researchers often assume that little bias is associated with estimating survival and behavioral parameters associated with this technique. However, researchers have not adequately examined these effects on organisms being investigated and have thus assumed demographic information obtained from such methods are valid. In light of this conjecture, it is imperative to evaluate methodological assumptions to ensure research is statistically valid and biologically meaningful. Therefore, we used Burnham's model and program MARK to analyze survival estimates of individually banded and radiotagged bobwhites during an 8-year period (1997–2004) consisting of 6,568 individuals (2,527 radiotagged) via combined analysis of mark—recapture, dead recovery (via harvest), and radiotelemetry data to test the effects of radiotransmitters on bobwhite survival. We also compared band—recapture survival estimates to Kaplan—Meier survival estimates, and we examined the effects of various other factors (e.g., temporal, spatial) on bobwhite survival. Based on Akaike's model selection criterion, the best model including the radiotransmitter covariate (Akaike's Information Criterion adjusted for small sample size bias and overdispersion relative value = 0.72) did not explain more of the variation in survival than models without this effect. Thus, we found the effect of radiotransmitters as negligible. Bobwhite survival varied relative to spatial (e.g., site), temporal (e.g., yr and season), and gender effects. Average annual survival for the 8-year period was 22.76% (1.50 SE) for banded-only and 21.72% (1.49 SE) for radiotagged birds. Survival rate varied annually, ranging from 12.42% (7.51 SE) to 37.16% (8.27 SE), and seasonally, ranging from 23.82% (2.71 SE) to 65.06% (3.23 SE); however, between group (banded-only, radiotagged) survival differences were still inconsequential. We conclude that for our study, radiotelemetry provided reliable survival estimates of an intensively managed bobwhite population, where supplemental food was provided, and this information provided useful data to make practical habitat management decisions. We believe that future radiotelemetry studies would benefit as a whole if researchers conducted similar analyses prior to presenting their results from radiotelemetry data, especially for populations that are more food limited.