Social organisation of thornbill-dominated mixed-species flocks using social network analysis
Date
2013
Authors
Farine, D.R.
Milburn, Peter J
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Publisher
Springer
Abstract
Mixed-species associations are a widespread phenomenon, comprising interacting heterospecific individuals which gain predator, foraging or social benefits. Avian flocks have traditionally been classified as monolithic species units, with species-wide functional roles, such as nuclear, active, passive, or follower. It has also been suggested that flocks are mutualistic interactions, where niches of participating species converge. However the species-level perspective has limited previous studies, because both interactions and benefits occur at the level of the individual. Social network analysis provides a set of tools for quantitative assessment of individual participation. We used mark-resighting methods to develop networks of nodes (colour-marked individuals) and edges (their interactions within flocks). We found that variation in flock participation across individuals within species, especially in the buff-rumped thornbill, encompassed virtually the entire range of variation across all individuals in the entire set of species. For example, female, but not male, buff-rumped thornbills had high network betweenness, indicating that they interact with multiple flocks, likely as part of a female-specific dispersal strategy. Finally, we provide new evidence that mixed-species flocking is mutualistic, by quantifying an active shift in individual foraging niches towards those of their individual associates, with implications for trade-off between costs and benefits to individuals derived from participating in mixed-species flocks. This study is, to our knowledge, the first instance of a heterospecific social network built on pairwise interactions.
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Keywords
Keywords: behavioral ecology; foraging behavior; individual variation; mark-recapture method; quantitative analysis; social network; social organization; songbird; trade-off; Acanthiza reguloides; Aves Foraging niche; Group living; Individual variation; Mixed-species flock; Social network analysis
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Source
Behavioral Ecology and Sociobiology
Type
Journal article
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Restricted until
2037-12-31
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