Prey killing by Eurasian Kestrels: the role of the foot and the significance of bill and talons

The technique used by birds of prey to kill their quarry has rarely been described in detail. Although it is common to watch a raptor hunting, distance and natural obstacles normally prevent the observer from observing what actually happens to the prey after being grasped by the bird. Therefore, we studied the predatory sequence and killing technique displayed by a sample of ten wild Eurasian Kestrels temporarily held in captivity because of various injuries. They were offered individually either a laboratory mouse or young laboratory rat. Direct observation was complemented by necropsy of the prey confirming that bill strikes frequently observed after grasping the prey are not used to kill it but merely to damage its central nervous system thereby minimising escape attempts. Furthermore, talons are not used as weapons al all, but only as tools that elongate the toes to hold the quarry more firmly. In contrast, several signs indicating death by suffocation were regularly found and these were confirmed by inspection of rodents sacrificed by CO2. We also discuss a hypothesis explaining the adaptive and evolutionary significance of the kestrel's use of toe pressure to kill the prey rather than using its obvious weapons.