Pre- To Post-Fledging Carryover Effects ReflectTrade-Offs that Explain Life History Variationamong Altricial Songbirds

Phenotypic traits acquired in one life history stage cancarryover and affect survival in subsequent stages. Suchcarryover effects are particularly relevant in young ani-mals, as early life stages are thought to be critical withrespect to animal life history evolution and populationdynamics. In juvenile songbirds, carryover effects fromthe pre- to post-fledging period may be critical for sur-vival, population viability, and life history evolutionbut remain poorly understood. To assess potential fac-tors driving life history variation in songbirds, our re-search tested whether wing development carries over toinfluence patters of post-fledging survival within andamong species. Our initial efforts focused on a sin-gle species, the Dickcissel (Spiza americana), where wefirst documented carryover effects of wing developmentduring the early post-fledging period. Subsequently, we broadened our study to examine carryover effectsamong 20 co-existing species of an avian communityin east-central Illinois, USA. We found evidence forpre- to post-fledging carryover effects at both the intra-and interspecific level, by which species and individualswithin a given species that fledged at earlier ages hadless developed wings, exhibited poorer flight ability,and experienced higher rates of mortality after fledging.Fledging age was ultimately the result of trade-offs withpredation risk, with higher nest mortality rates favor-ing shorter nestling periods and less developed wings.Ultimately, our results show how morphological traits,locomotor performance, and age-specific mortality cantrade-off and interact across juvenile life stages to shapeanimal life histories.