Simple local interactions explain complex aerial displays of thousands of starlings

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 through video recordings and position measurements by stereo photography, there are as yet no models that generate these complex patterns. Recent 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 investigated whether this approach can be extended to generate patterns resembling these aerial displays of starlings. We show in a model that to generate these patterns we have to extend the usual rules of local coordination with a few specifics of starling behaviour, namely 1) their aerial locomotion, 2) a low and constant number of interaction-partners and 3) preferential movement above a ‘roosting area’. Most of the empirical patterns of real starlings in proximity of an urban roost emerged in our model. Our results provide new understanding of the mechanisms underlying these displays and of swarming patterns in biological systems in general. Our model can be used as a tool to increase our understanding of these displays.