Eggshell water vapor conductance (GH₂O), shell thickness (T), and effective pore area (Ap) of eggs from pigeons (Columba livia) nesting under extreme conditions (high ambient temperatures and low humidity) were compared with those of urban pigeons and pure rock doves breeding in mesic conditions. Heat-acclimated pigeons had eggshells characterized by ∼30%-40% lower than predicted GH₂O. A significantly reduced Ap and higher than predicted shell thickness accounted for the observed reduction in GH₂O. We conclude that these pigeons were physiologically adapted to successfully breed under extreme conditions prevailing in their original colony.
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Arad et al. (1988) studied this question.