Innate plasticity of a predatory behavior: nonlearned context dependence of avian flush-displays

摘要

If a foraging adaptation comprises a signal for sensory exploitation of prey, does the behavior and its use develop through learning, like many foraging behaviors or does it depend on nonlearned stereotypical motor actions, like many signals for sensory exploitation? We asked whether the visually conspicuous motor pattern of body pivoting with spread tail and wings used by the painted redstart (Myioborus pictus) to flush insect prey is a nonlearned phenotypic trait. The motion pattern and the increase in these displays under branches (context dependence based on physical properties of the habitat) help the wild birds in foraging because prey that rest on substrates is visually stimulated, flushed into the air, and consequently chased in aerial pursuits. In unrewarded conditions in the aviary, both the foraging-experienced adults and the foraging-naive hand-raised fledglings increased the frequency of flush-displays at locations with substrates above birds, recreating the pattern of foraging observed in adults in their natural habitats. The results imply that parent–offspring cultural transmission or learning during foraging is not required for the development of both the display motion pattern and the adaptive context-dependent increase in display frequency. Such a nonlearned context dependence based on physical properties of the habitat is remarkable considering that avian foraging context-dependent plasticity is often based on learning. We hypothesize that this innate character of the signals may be a result of evolution to exploit universal properties of visually triggered escape behaviors of various insects that are predictably flushed from their resting sites in the habitat.