Aerial displays of starlings (Sturnus vulgaris ) at their communal roosts are complex: they consist of multiple flocks of thousands of individuals which are continually changing shape and density, while splitting and merging. To understand these complex displays both empirical data and models are needed. Whereas detailed empirical data were recently collected of flocks of thousands of starlings, there are as yet no models that generate these complex patterns. Numerous computer models in biology, however, suggest that patterns of single groups of moving animals may emerge by self-organisation from movement and local coordination (through attraction, alignment and avoidance of collision). In this talk, we show that to generate in a model most of the empirical patterns measured in real starlings we have to extend the usual rules of local coordination with a few specifics of starling behaviour, namely 1) their aerial locomotion and in particular rolling during turning, 2) a low and constant number of interaction-partners and 3) preferential movement above a sleeping site. Our model provides new hypotheses about the mechanisms underlying these displays and of swarming patterns in biological systems in general.
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