From flocking propensity to within-flock association: A two-stage framework for mobile interaction networks in mixed-species bird flocks

Whole-body plumage dichromatism showed no clear effect, although body-part-specific analyses revealed a localized positive effect of forewing achromatic dichromatism. At the second stage, within-flock association strength was greater among species that were more similar in body size and HWI, shared diet and foraging stratum, and were more closely related. HWI similarity was the most consistently supported predictor, with support in eight of ten local networks.

Whole-body plumage similarity showed no consistent effect, although localized body-part-specific signals emerged. Overall, the two stages showed partly distinct trait patterns: flocking propensity was associated primarily with body size and foraging stratum, whereas within-flock association strength was structured mainly by functional and phylogenetic matching. This two-stage framework, coupled with avian visual modeling, provides a general approach for understanding how mobile interaction networks assemble across taxa.