used attraction, alignment and avoidance and extended this with a number of traits of real starlings: first, birds fly according to fixed wing aerodynamics, while rolling when turning (thus losing lift); second, they coordinate with a limited number of interaction neighbours of 7 (like real starlings); third, they try to stay above a sleeping site (like starlings do at dawn), and when they happen to move outwards from the sleeping site, they return to it by turning; fourth, they move at relative fixed speed. The authors showed that the specifics of flying behaviour as well as large flocksize and low number of interaction partners were essential to the creation of the variable shape of flocks of starlings.