Effects of Calcium‐Loading on Egg Production in Ring‐Necked Pheasants

Abstract

Abstract: Ring‐necked pheasants (Phasianus colchicus) are able to store dietary calcium as medullary bone, which they may mobilize for future eggshell synthesis. We define this mechanism as calcium‐loading. Previous experiments on pheasants conducted to document the importance of calcium in limiting distribution did not account for calcium‐loading. We hypothesized that calcium‐loading could override experimental calcium treatments of the diet. We measured egg production, egg characteristics, and femoral mineral content for pheasants that were not calcium‐loaded on 7 diets differing in calcium from 0.2% to 4.5% and compared these results to a similar study on calcium‐loaded pheasants. We predicted that calcium‐loaded pheasants would produce more eggs than those that were not calcium‐loaded. We also predicted that there would be no significant difference between femur ash fractions in non‐calcium‐loaded pheasants, but that the ash fraction in calcium‐loaded pheasants would differ significantly between the beginning and end of the experiment. Egg production was higher in calcium‐loaded pheasants above 2% dietary calcium. Femur ash fraction was not different in non–calcium‐loaded pheasants but differed significantly before and after the experiment and between high (>2%) and low (<2%) dietary levels in calcium‐loaded pheasants. Calcium‐loading may account for short‐term persistence of captive pheasants introduced on calcium‐poor soils, followed by their eventual population failure. Managers may improve survival of captive pheasants before introduction by surveying habitat for adequate calcium and by calcium‐loading.