Eberhart-Phillips, Luke J.Küpper, ClemensCarmona-Isunza, María CristinaVincze, OrsolyaZefania, SamaCruz-López, MedardoKosztolányi, AndrásMiller, Tom E.X.Barta, ZoltánCuthill, Innes C.Burke, TerrySzékely, TamásHoffman, Joseph I.Krüger, Oliver2018-08-172018-08-172018Eberhart-Phillips, Luke J., Küpper, Clemens, Carmona-Isunza, María Cristina, et al.. "Demographic causes of adult sex ratio variation and their consequences for parental cooperation." <i>Nature Communications,</i> 9, (2018) Springer Nature: https://doi.org/10.1038/s41467-018-03833-5.https://hdl.handle.net/1911/102468The adult sex ratio (ASR) is a fundamental concept in population biology, sexual selection, and social evolution. However, it remains unclear which demographic processes generate ASR variation and how biases in ASR in turn affect social behaviour. Here, we evaluate the demographic mechanisms shaping ASR and their potential consequences for parental cooperation using detailed survival, fecundity, and behavioural data on 6119 individuals from six wild shorebird populations exhibiting flexible parental strategies. We show that these closely related populations express strikingly different ASRs, despite having similar ecologies and life histories, and that ASR variation is largely driven by sex differences in the apparent survival of juveniles. Furthermore, families in populations with biased ASRs were predominantly tended by a single parent, suggesting that parental cooperation breaks down with unbalanced sex ratios. Taken together, our results indicate that sex biases emerging during early life have profound consequences for social behaviour.engThis article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder.Journal articles41467-018-03833-5https://doi.org/10.1038/s41467-018-03833-5