Eq. 3
Where is the daily water loss, C is a conversion constant (155.52*107/R*T, where R is the ideal gas constant:6.24*104cm3*Torr/mol*°K, and T is absolute temperature in °K), is the diffusion coefficient of water in air at a given temperature (in °C), Ap/L is porosity, and the difference in pressure across the eggshell. From this using equation 3.5 water vapour conductance of whole eggs at 25 and 0% humidity was calculated and compared with the results reported by Calder (1978) and Silyn‐Roberts (1983) for Brown Kiwi, and with the values reported by Ar et al. (1974) for other avian species.
The water vapour conductance was calculated by using the daily water loss calculated from equation (3) in equation (1). Finally, to compare our results with allometric predictions we calculated the water vapour conductance for those eggs based on Ar et al. (1974):
\(G_{H_{2}\text{O\ \ }}=0.432*W^{0.780}\) Eq. 4
Where W is the fresh weight of the egg, in this case we used the arrival weight of the eggs since there was no way to know the fresh egg weight. In this measurement only Brown Kiwi eggs were used as were the only ones that were weighed before hatching so the water loss could be determined.