Effects of foliar insecticides on survival of northern bobwhite quail chicks

Reduced survival of chicks may result from exposure to insecticides and may explain declines in northern bobwhite quail (Colinus virginianus) populations on agricultural landscapes. To determine the risk insecticides pose to quail, we quantified exposure rates and hazard. Exposure rate depends on quail habitat use in relation to insecticide applications, whereas hazard depends on susceptibility to a toxin and the dose an individual receives. Because providing early-successional vegetation around row-crop fields is a typical habitat management recommendation, we determined rates of exposure of quail and their broods to insecticides applied to soybean fields with and without vegetated field borders. Radiocollared quail (n = 69) used soybean fields extensively (64% of telemetry locations) at the time of year insecticides were applied. Quail used soybean fields twice as often when vegetated borders surrounded crop fields (P = 0.04). Ten of 18 broods monitored by telemetry were located in soybean fields 88% of the time. In 1993, 4 of 6 broods 0.49). However, ChE activity was depressed (P < 0.001) and body mass was lower (P = 0.02) in chicks exposed to methyl parathion, which historically (pre-1980) received significant use in production of row crops in North Carolina. Our results, along with data on use and toxicity of other insecticides applied to row crops, collectively suggest direct affects to survival of quail chicks from use of foliar-applied insecticides does not explain reduced quail densities on agricultural landscapes.