Attacking predators and fleeing prey : detection, escape and targeting behaviour in birds

Abstract: The aim of this thesis is to further our understanding of predator and prey behaviour and decision making in different attack situations. The thesis deals with escape strategies, predator detection ability and prey targeting behaviour. Thus the thesis includes several aspects of a predation event and it includes studies both on prey animals and predators. In the first paper we show that blue tits (Parus caeruleus), a small passerine bird, are highly flexible in their escape behaviour and adjust their escape to the detailed behaviour of an attacking predator. The predator’s attack height influenced the blue tits’ ascent angles whereas attack speed influenced the lateral course of the flight. These escape responses might reflect a turning gambit between prey and predator. To adjust escape behaviour might therefore be very important for survival. Our result from the second paper suggests that the evolution of flexible escape behaviour is influenced by habitat and life style. We found that open living bird species adjusted their escape behaviour to the behaviour of a predator to a higher degree than skulky, cover living bird species did. The third paper deals with how different aspects of foraging influence blue tits’ ability to detect predators and time till take-off. Detection ability in prey can heavily affect their likelihood to escape successfully. The body posture of the blue tits (head-up or head-down) did not affect their detection ability whereas their orientation did; detection was delayed when the attack came from behind. Foraging behaviour is often assumed to delay predator detection but we could not find any negative effect of an easy foraging task. A difficult task, on the other hand, severely delayed detection of the predator and time to take-off. In the last paper we investigate if sparrowhawks (Accipiter nisus) hunting opportunistically can discriminate between prey birds on the basis of vigilance state and preferentially target foraging birds for attack. The sparrowhawks showed no preference for foraging prey which is in contrast to predators which inspect their prey before attack. Thus our results suggest that predators may only have time to discriminate between individuals on the basis of vigilance state when stalking.