Analysing age structure, residency and relatedness uncovers social network structure in aggregations of young birds. (August 2020)

• Record Type: Journal Article
• Authors: Franks, Victoria R.; Ewen, John G.; McCready, Mhairi; Rowcliffe, J. Marcus; Smith, Donal; Thorogood, Rose
• Is Part Of: Animal behaviour. Volume 166(2020)
• Page Start: 73
• Page End: 84
• Publication Date: 2020-08
• Subjects: gang -- juvenile -- passerine -- social groups -- social networks; Animal behavior -- Periodicals; 591.5
• DOI: 10.1016/j.anbehav.2020.06.005
• Languages: English
• ISSNs: 0003-3472

Abstract

Abstract : Animal sociality arises from the cumulative effects of both individual social decisions and environmental factors. While juveniles' social interactions with parents prior to independence shape later life sociality, in most bird and mammal species at least one sex undergoes an early life dispersal before first-year reproduction. The social associations from this period could also have implications for later life yet are rarely characterized. Here, we derived predictions from available examples of juvenile groups in the literature (mobile 'flocks', spatially stable 'gangs' or adult-associated 'crèches') and then used three cohorts of juvenile hihi, Notiomystis cincta, a threatened New Zealand passerine, to demonstrate how multistate modelling and social network analysis approaches can be used to characterize group type based on residency, movement, relatedness and social associations. At sites where hihi congregated, we found that juveniles were resighted at a higher frequency than adults and associated predominantly with unrelated juveniles rather than siblings or parents. Movement between group sites occurred, but associations developed predominantly within the sites. We suggest therefore that juvenile hihi social structure is most similar to a 'gang', a group structure in which juveniles congregate without adults at predictable sites. Such gangs have previously only been described formally in ravens, Corvus corax . By combining spatial and social network analyses, our study demonstrates how social group structures can be described and therefore facilitate broader comparisons and discussion about the form and function of juvenile groups across taxa. Highlights: Early life social behaviour once young leave parents is poorly understood. We characterize group structure and social associations in a passerine bird. Juveniles associated with unrelated juvenile peers rather than siblings or parents. Social structure resembled 'gangs' which have few empirical examples. Describing social structure can help us understand early life social environment.