Methods for artificial incubation of passerine eggs.

Climate change is leading to higher and more variable temperatures worldwide, and these changes are likely to have consequences on the incubation stage of egg-laying organisms. Artificial incubation can be used to address a variety of mechanistic, ecological, and conservation questions related to the development of egg-laying animals in a warming climate. Artificial incubation of passerine eggs remains rare because their eggs can be highly sensitive to incubation conditions, causing it to be challenging to successfully incubate their eggs to hatch in captivity. The goal of this study was to describe a protocol to artificially incubate eggs of house sparrows (Passer domesticus), a widespread model species, and to provide a framework that can be used to develop protocols for artificial incubation of other passerine species. Since sufficient egg mass loss is necessary for proper development and can be related to hatching success, we monitored mass loss of eggs in natural nests in the field and used this information to inform and modify artificial incubation conditions. We found that eggs in our study population lost an average of 11.34% of their original mass across the incubation period, and that mass loss was greater later in incubation. To identify conditions promoting high hatching success, we tested incubation conditions of 36.9°C-37.4°C, 40-50% relative humidity (RH), and automatic and hand egg turning. We achieved 100% hatching success of artificially incubated eggs using a rocking incubator with automatic turning (90°/hour) and three 180° hand turns per day, incubation conditions of 37.36°C and 42.6% RH, and hatching conditions of 36.73°C and 57.9% RH. These conditions and the framework we provide to develop incubation protocols for other passerine species can be applied to better understand how changing environmental conditions are affecting the development of egg-laying organisms.