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Demographic causes and social consequences of adult sex ratio variation
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  • Published: 06 April 2026

Demographic causes and social consequences of adult sex ratio variation

  • Zitan Song  ORCID: orcid.org/0000-0001-9739-02331,2,
  • András Liker3,4,
  • Yang Liu  ORCID: orcid.org/0000-0003-4580-55185,
  • Robert P. Freckleton  ORCID: orcid.org/0000-0002-8338-864X6 &
  • …
  • Tamás Székely7,8,9 

Nature Communications , Article number:  (2026) Cite this article

We are providing an unedited version of this manuscript to give early access to its findings. Before final publication, the manuscript will undergo further editing. Please note there may be errors present which affect the content, and all legal disclaimers apply.

Subjects

  • Behavioural ecology
  • Coevolution
  • Sexual selection

Abstract

The adult sex ratio plays a crucial role in shaping breeding systems and traits linked to sexual selection. Recent studies associate adult sex ratio with mate choice, pair-bonding, and parenting, as the rarer sex gains advantages in mate selection and parental investment. However, the causal relationships between the demographic factors that generate adult sex ratio bias and its broader implications remain debated. Skewed adult sex ratios can result from sex-biased mortality and maturation, which influence mating and parental behaviours. Conversely, the costs of these behaviours may further drive sex differences in mortality and maturation, reinforcing adult sex ratio biases. Here, we compile demographic and behavioural data from 261 bird species across 69 families to examine these associations within a phylogenetic framework. Our analyses confirm that demographic traits are associated with adult sex ratio and reveal links between adult sex ratio, pre-copulatory sexual selection, and parenting. Phylogenetic path analyses further demonstrate that sex differences in mortality and maturation drive adult sex ratio biases, which subsequently influence mating and parenting rather than the reverse. This study provides a comprehensive analysis of the interplay between demography, social environment, and breeding systems, highlighting adult sex ratio as a crucial link. Our findings underscore the need for further research on the demographic underpinnings of social behaviour and reproductive strategies.

Data availability

The data used in this study are available in Figshare (https://doi.org/10.6084/m9.figshare.31490812)79. The Figshare repository includes the dataset used in the analyses and the phylogenetic trees used for phylogenetic mixed models and for generating Fig. 2. Data underlying Figs. 3 and 4 are provided in Table 1 and Supplementary Table 5. Source Data are provided for Fig. 5 and Supplementary Fig. 4. Source data are provided with this paper.

Code availability

The code used for data preparation, statistical analyses, and figure generation is available in Figshare (https://doi.org/10.6084/m9.figshare.31490812)79.

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Acknowledgements

We thank Bálint Kovács for extracting some of the data used in the analyses. This work was supported by the National Research, Development and Innovation Office of Hungary to TS (HUN-REN–Debrecen University Reproductive Strategies Research Group, Ref. 1102207, ADVANCED 150852, HU-RIZONT-2024-00109). RPF and TS were supported by the Hungarian Academy of Sciences Guest Professorship scheme 2024-47. AL received funding from the HUN-REN TKI Hungarian Research Network (HUN-REN–PE Evolutionary Ecology Research Group, Ref. 16007) and was also supported by the National Research, Development and Innovation Office of Hungary (ADVANCED 150703).

Author information

Authors and Affiliations

  1. Co-Innovation Center for Sustainable Forestry in Southern China, College of Life Sciences, Nanjing Forestry University, Nanjing, China

    Zitan Song

  2. Comparative Socioecology Group, Department for the Ecology of Animal Societies, Max Planck Institute for Animal Behavior, Konstanz, Germany

    Zitan Song

  3. HUN-REN-PE Evolutionary Ecology Research Group, University of Pannonia, Veszprém, Hungary

    András Liker

  4. Behavioral Ecology Research Group, Center for Natural Sciences, University of Pannonia, Veszprém, Hungary

    András Liker

  5. State Key Laboratory for Biocontrol, School of Ecology, Sun Yat-sen University, Shenzhen, China

    Yang Liu

  6. School of Biosciences, University of Sheffield, Sheffield, UK

    Robert P. Freckleton

  7. Milner Centre for Evolution, Department of Life Sciences, University of Bath, Bath, UK

    Tamás Székely

  8. HUN-REN-DE Reproductive Strategies Research Group, Department of Evolutionary Zoology and Human Behaviour, University of Debrecen, Debrecen, Hungary

    Tamás Székely

  9. Department of Ethology, Eötvös Loránd University, Budapest, Hungary

    Tamás Székely

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  1. Zitan Song
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  2. András Liker
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  3. Yang Liu
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  4. Robert P. Freckleton
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  5. Tamás Székely
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Contributions

T.S. and Z.S. developed the concept of the study and wrote the first draft, Z.S. and A.L. prepared the data, Z.S. analysed the data, supported by A.L. and R.P.F., Y.L. provided feedback on the study design and manuscript, and all authors contributed to revising the manuscript.

Corresponding authors

Correspondence to Zitan Song or Tamás Székely.

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Song, Z., Liker, A., Liu, Y. et al. Demographic causes and social consequences of adult sex ratio variation. Nat Commun (2026). https://doi.org/10.1038/s41467-026-71230-4

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  • Received: 08 May 2025

  • Accepted: 17 March 2026

  • Published: 06 April 2026

  • DOI: https://doi.org/10.1038/s41467-026-71230-4

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