Pairs of 1st-year breeding bobwhites were fed constant or decreasing concentrations of monocrotophos for 15 days. In addition, a control diet was used in a pair-fed group matched with the pairs in the constant group. Dietary concentrations for the constant group were logarithmically spaced at .100, .178, .316, .562, 1.000 ppm of actual insecticide and also at 0 ppm (control) for five pairs at each concentration. The beginning concentrations for the decreasing pairs were identical to the constant group but regularly decreased to reach 25% of the starting concentrations by Day 13. Food consumption, egg production, hatchability of eggs under artificial incubation, and survival of hatched chicks for 2 weeks were recorded pairwise during 15-day treatment and 14-day posttreatment periods. Mortality was high at the greatest constant concentration and in the associated pair-fed group. Food consumption and egg production rates were negatively dose-related during the treatment period in the constant and decreasing groups. The laying rate of pair-fed hens was reduced to the same extent as in the constant group. Reproductive inhibition was not permanent, and pairs resumed laying after a dose-related recovery interval. No dose-related effects on hatchability or chick survival were detected. There was no evidence of a pesticide effect on reproduction other than that exerted through pesticide-induced anorexia.
