Variation in Egg Size of the Hooded Crow Corvus corone cornix

Abstract

Variation in egg size of a population of the Hooded Crow Corvus corone cornix was studied at Trondheim in Central Norway, during the period 1979-1982. No significant differences in egg volume were found neither from one year to another nor within different sized clutches, nor with laying date. The hatchability of small sized eggs and of eggs laid late in the laying order was lower than that of large sized eggs and of eggs laid early in the laying order. For all clutch sizes, a decrease in egg volume was found with increasing order of laying. All the last laid eggs (n = 39) had a smaller volume than the mean for the same clutch. The relative size of the first laid eggs (deviation from the mean for the same clutch) decreased with increasing clutch size. A significant positive correlation existed between the body weight of the hatchling and the volume of the egg from which it hatched. Both male and female hatchlings hatched from eggs of similar size, and had roughly the same body weights at hatching.