Is Foot Squeezing Pressure by Two Raptor Species Sufficient to Subdue Their Prey?

We quantified foot squeezing pressure exerted by Common Buzzards (Buteo buteo) and Eurasian Kestrels (Falco tinnunculus) while grasping a rodent. The birds were offered either a dead laboratory mouse, a fake mouse consisting of a laboratory mouse skin surrounding a rubber pipe connected to a pressure transducer, or a live laboratory mouse. Direct observations and necropsy of the depredated mice confirm death by suffocation from the raptor's grasp. The two raptor species differed in technique of constricting the fake mouse: the buzzard relied on strong, but very brief squeezing bouts, whereas the kestrel compensated for less squeezing strength by performing constriction with prolonged duration. When observed, bites to the head were consistent with immobilizing live prey but not killing it. In contrast, squeezing by thoracic compression is sufficient to kill the prey without the need to use beak or talons.