Ecological importance of the thermal emissivity of avian eggshells

Breeding birds have to divide their time between egg incubation and foraging. Particularly in cases when only one parent incubates the eggs, and especially in cold climates, the cooling of the eggs during absence from the nest may be problematic. In the present study we find that the thermal emissivity of eggshells may be ecologically important, and that an evolutionary pressure towards lower emissivity for exposed eggs in cold climates exists. We plan to experimentally compare emissivities among species in a future study.

► Cooling rate of bird eggs depends on eggshell thermal emissivity.
► Lower emissivity allows parents to leave nest longer for feeding.
► Emissivity is likely to adapt to behavior and climate.