Effect of nutritional deficiency on ruffed grouse condition and reproductive success

Maternal body fat condition (i.e., percent carcass fat) is often a focal point in determining reproductive success in female galliforms. Previous research has centered around habitat-related nutritional parameters affecting body condition and the influence on reproductive capacity. Past studies have shown that ruffed grouse (Bonasa umbellus) maintain higher mean body fat levels throughout the Appalachians and variation in body condition exceeds that found in northern grouse. In the Appalachians, ruffed grouse with diets devoid of energy-rich hard mast have lower body fat condition. It has been hypothesized that females in poorer condition will have lower productivity in the Appalachians. We conducted a 2-year study of captive Appalachian ruffed grouse (subspecies Bonasa umbellus monticola) to assess the effects of 4 treatment rations varying in dietary energy and crude protein on female body condition throughout the pre-breeding and reproduction periods using total body electrical conductivity (TOBEC) technology. Females on low protein rations maintained higher carcass fat levels than females on high protein treatments, although high protein treatments led to less fat loss during reproduction. High-energy rations produced females with higher fat levels prior to reproduction; however, adult females on high-energy treatments lost more fat during reproduction than low-energy treatments. We posit that the presence of low-protein, high-energy feed items in diets of Appalachian ruffed grouse potentially lead to higher percent body fat, whereas high-protein diets support leaner grouse. We also determined the effect of body fat condition on onset of laying, egg quality, clutch size, and chick mass at hatch. Our experimental treatment rations stratified females into differing fat condition classes, ranging from 3.9--43.5% body fat. Although egg composition differed among condition classes, we found no evidence of a relation between fat condition and egg composition. Female grouse were capable of producing comparable eggs, clutches, and chicks across varying planes of body fat condition. Our results suggest that the effect of increased fat reserves in Appalachian ruffed grouse does not directly influence fecundity. We propose that any influence female condition has on fecundity and chick survival is enacted after the nesting effort is complete