Funding for this research was provided by:
Nederlandse Organisatie voor Wetenschappelijk Onderzoek (040.11.573/ 1798, 040.11.468)
Stichting voor de Technische Wetenschappen (14723)
Text and Data Mining valid from 2019-08-15
Received: 8 February 2019
Revised: 17 July 2019
Accepted: 29 July 2019
First Online: 15 August 2019
Compliance with ethical standards
: The authors declare that they have no conflict of interest.
: This study is purely observational and did not involve captive animals or experimental manipulations, only analyses of video material. The video recordings of the flocks and falcons were taken from hundreds of meters distance in an urban environment and did not cause any disturbance to the birds.