Robotic predators induce consistent collective escape responses and may trigger massive displacements of avian prey

Avian collective behaviours, arising from associations of similarly behaving individuals in flocks, can create conflicts with human activities, resulting in safety hazards, hygienic issues and economic losses. Many methods have been developed to disperse birds or prevent their gathering from specific locations, with variable effectiveness but usually high habituation rate. Recently, a new promising method has been proposed. It consists of a flying, remotely controlled robotic predator (RobotFalcon), mimicking the hunting behaviour of a bird of prey, which can be flown towards bird flocks. Taking advantage of the deeprooted escape response of many avian prey species to aerial predators and it being completely controllable, the RobotFalcon is expected to be highly effective and not affected by habituation. We used a robotic peregrine falcon (Falco peregrinus) to assess type and consistency of the escape response of two highly gregarious species, feral pigeons (Columba livia var. domestica) breeding and feeding in a cattle farm (ca. 500 individuals) and black-headed gulls (Chroicocephalus ridibundus) roosting in a wastewater treatment plant (ca. 8000 individuals). We repeatedly exposed flocks to the RobotFalcon and analysed their collective escape behaviour across multiple daily flight sessions (pigeons: n = 10 and gulls: n = 5) using video-recordings. The escape responses and the presence around the roost before, during and after the deterrence actions of black-headed gulls were also monitored by radar. Our results show that robotic predators induce consistent collective escape response in both species without signs of short-term habituation and that it may displace even huge flocks from their gathering sites.