Don’t count your chicks before they hatch: reproductive allocation and nesting success in birds (#901)
Variation in parental effort is substantial across species and driven by life-history and ecology, however in birds this variation is mainly assessed at the egg stage. Thus, it remains unclear how reproductive effort is allocated across the stages of reproduction and ultimately translates into realized reproductive success. Using across-year data of 65 species, we examined the relationships between annual reproductive allocation, inter-annual variability in allocation and reproductive success across nesting stages. Controlling for phylogeny, life history and ecology, we found that the traits which account for differences in fecundity did not influence the realized reproductive success. Nest success, but not fecundity, was affected by the level of post-fledging parental care. In particular, extended parental care was related to lower reproductive success, demonstrating a trade-off between pre- and post-fledging parental investment. These findings highlight that variation in fecundity may not reflect variation in reproductive success, and that the factors selecting for each are distinct. Thus, fecundity, the focus of many avian life history studies, gives only partial insight into the evolutionary processes shaping life-history evolution; considering the allocation trade-offs between components of reproduction is required to fully understand these processes.