Avian eggshell conductance varies with life-history

Credit: Pixlab.co.za. Image cropped.

Embryo survival in birds depends on a controlled transfer of water vapour and respiratory gases through the eggshell, and this exchange is critically sensitive to the surrounding physical environment. As birds breed in most habitats around the world, it has been proposed that variation in eggshell conductance has evolved to optimise the viability of embryonic development under different breeding conditions. Our aim was to evaluate how climate and life-history influence eggshell conductance of after accounting for the effects of adult body mass and phylogeny.

Our study uses whole egg water vapour conductance data of 364 bird species sampled across avian phylogeny. All eggs used in laboratory experiments were obtained from the Natural History museum, Tring. Eggs were filled with water through a small hole made in the shell, then placed in a chamber at 0% humidity. Each egg was weighed every 24 hours to assess water loss through the eggshell over time. These measures were compared across species using phylogenetic comparative methods to assess the importance of life-history and phylogeny. The manuscript is currently under review, but we’ll tell you the results once it is published.

Whole eggs filled with water were placed inside a sealed chamber filled with silicone crystals to measure the amount of water lost every 24 hours. Credit: Marie Attard

IN PRESS

Attard MRG and Portugal SJ (In Press) Climate variability and mode of development influence gas exchange across avian eggshells. Proceedings of Royal Society B.