Incubation temperature and social context affect the nest exodus of precocial ducklings

The environments that animals experience during development have important fitness consequences. In birds, parents influence the developmental environment of their offspring through incubation. Subtle changes in incubation temperature affect offspring morphology and physiology, such as growth, immune function, and thermoregulation, yet little is known about how it may affect critical early-life behaviors. Because expression of behavior can be influenced by the social environment, the effect of incubation temperature on behavior may be context-dependent. We investigated whether incubation temperature and social context influence a critical early-life task in wood ducks (Aix sponsa). Wood ducks nest in tree cavities and, shortly after hatching, ducklings must jump and climb out of the cavity. Failure to exit the nest is fatal. In 2 experiments, we incubated eggs at different mean temperatures and examined the nest exodus of ducklings individually and in mixed-incubation temperature pairs. When tested individually, ducklings incubated at 35.8 °C and 37.0 °C were ~2.5 times more successful at exiting the nest, and jumped and climbed more often, than those incubated at 35.0 °C. However, in an experiment conducted the following year, we found that social interactions mitigated these effects and there was no difference in nest exodus success when ducklings incubated at 35.0 °C and 36.0 °C were tested together in pairs. This may be because, when in pairs, ducklings incubated at the low-temperature experience social enhancement whereas those incubated at the high temperature maintain similar behaviors. These results advance our understanding of how parental effects influence offspring behaviors and performance within different social contexts. Poor conditions during development lead to suboptimal offspring behaviors, but this can be mitigated by social interactions. Shortly after wood duck ducklings hatch, they must jump out of their nest in a tree cavity. Failure to exit is fatal. Ducklings that hatch from eggs incubated at low temperatures are less successful at exiting the nest than those incubated at higher temperatures when tested individually, but success is similar when ducklings experience social interactions in pairs.