Effect of Eggshell Thinning on Water Vapor Conductance of Malleefowl Eggs

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Abstract
The water vapor conductance of eggs of mound-nesting Malleefowl (Leipoa ocellata) increases about three-fold during the 60-day incubation period. As the embryo absorbs calcium from the inside of the eggshell, mainly from the shoulder and equator the pore length decreases about 21% and the narrowest part of each pore is lost. Because the inner 21% of a pore accounts for about 85% of the resistance to gas diffusion in unincubated eggs, its loss greatly increases conductance. The increase in conductance of Malleefowl eggs is greater than that recorded for eggs of other birds, and appears to be a requirement for successful gas exchange in an underground environment.