SURVIVAL AND PESTICIDE EXPOSURE OF NORTHERN BOBWHITES (COLINUS-VIRGINIANUS) AND EASTERN COTTONTAILS (SYLVILAGUS-FLORIDANUS) ON AGRICULTURALFIELDS TREATED WITH COUNTER (R) 15G

During 1988 and 1989 northern bobwhites (Colinus virginianus) and east ern cottontails (Sylvilagus floridanus) were radiotagged and their dai ly survival monitored on six study sites treated with the organophosph orus insecticide-nematicide Counter(R) 15G (terbufos), at the rate of 1.45 kg a.i. per hectare, and on three reference sites. Nonlethal bloo d samples were collected at the time of capture and during subsequent recaptures to determine exposure to terbufos through blood ChE analysi s. Survival rates of radiotagged eastern cottontails and blood plasma ChE activities were not different between treated and reference sites in either year. Gastrointestinal (GI) tracts of two cottontail carcass es found in 1988 contained traces of terbufos in concentrations <0.046 ppm. No terbufos was detected in GI tracts in 1989. There were no dif ferences in survival rates of radiotagged northern bobwhites among tre atments. Mean blood plasma ChE activities of northern bobwhites were s ignificantly lower (P< 0.05) on treated sites than on reference sites both years, including sublethal exposure to the test chemical. No GI t ract residues were detected in bobwhites in 1988, and GI tract residue s were detected in trace amounts (<0.046 ppm) in only one bobwhite car cass in 1989.