Variable fledging age according to group size: Trade-offs in a cooperatively breeding bird

N. J. Raihani*, A. R. Ridley

*Corresponding author for this work

    Research output: Contribution to journalArticlepeer-review

    33 Citations (Scopus)

    Abstract

    Group living can provide individuals with several benefits, including cooperative vigilance and lower predation rates. Individuals in larger groups may be less vulnerable to predation due to dilution effects, efficient detection or greater ability to repel predators. Individuals in smaller groups may consequently employ alternative behavioural tactics to compensate for their greater vulnerability to predators. Here, we describe how pied babbler (Turdoides bicolor) fledging age varies with group size and the associated risk of nestling predation. Nestling predation is highest in smaller groups, but there is no effect of group size on fledgling predation. Consequently, small groups fledge young earlier, thereby reducing the risk of predation. However, there is a cost to this behaviour as younger fledglings are less mobile than older fledglings: they move shorter distances and are less likely to successfully reach the communal roost tree. The optimal age to fledge young appears to depend on the trade-off between reduced nestling predation and increased fledgling mobility. We suggest that such trade-offs may be common in species where group size critically affects individual survival and reproductive success.

    Original languageEnglish
    Pages (from-to)624-627
    Number of pages4
    JournalBiology Letters
    Volume3
    Issue number6
    DOIs
    Publication statusPublished - 22 Dec 2007

    Keywords

    • Fledging age
    • Group size
    • Nestling development
    • Pied babbler
    • Predation
    • Trade-off

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