Effects of visual stimuli, substrate-borne vibrations and air current stimuli on escape reactions in insect prey of flush-pursuing birds and their implications for evolution of flush-pursuers

Abstract

Insects use escape behaviors to avoid predators. Some insectivorous birds evolved a unique flush-pursue foraging technique that exploits their insect prey escape responses. Flush-pursers use visual stimulation from spreading of tails and wings and from pivoting body movements as well as plumage contrast to trigger escapes in prey. The escaping prey is subsequently pursued in aerial chases. By simulating approaches of one such flush-pursuer, the painted redstart (Myioborus pictus), to moths, flies, and homopteran insects we studied the effect of visual stimulation as well as possible effects of subtle air-currents from pivoting element of flush-displays and the effect of substrate borne vibrations that might be produced by moving bird. We confirm the importance of visual stimulation in triggering the prey escape behavior by flush-displaying birds. Effect of air currents was only important for relatively strong experimental air-puffs, which may approximate a situation of a bird displaying by moving its open tail and wings at a close distance to its prey. Substrate-borne vibrations positively contributed to the visually elicited escape reaction of moths. The results suggest that the visual predator-to-prey signal used by extant flush-pursuers for exploitative foraging could be aided in certain situations by substrate-borne vibrations or air currents produced by flush-displaying birds. Hypothetical role of non-visual stimuli in the initial evolution of flush-pursue strategy is discussed.