Accurate calculation of the content volume, density and original weight of museum curated eggs

Worldwide museums hold collections of eggshells representing material for descriptive studies. However, an obstacle to this is the lack of information about the original contents and weight of the entire egg (W). This study aimed to fill this gap though development of a methodological mechanism for calculating the volume of the egg interior (Vi), its density (Di) and W. To determine Vi, it is sufficient to measure four geometric dimensions of the egg and shell thickness. The Di value depends on the surface area-to-volume ratio (S/V) and can be calculated from an empirical relationship. For its derivation, data on 454 eggs from 447 avian species, 95 families and 13 orders were used. Imputing data on the contents and shell weight (Ws), we proposed a theoretical relationship for calculating W. We found a negative correlation between Di and S/V (which reflects the egg metabolism level) and suggest that a female in most species maintains the duration of egg incubation at a constant level that has practically an unchanged value for the respective species. A mathematical algorithm for calculating the Di value depending on the S/V ratio provides the missing link in calculating W of a whole egg from archived collection material.