Are Birds the Primary Selective Force Leading to Evolution of Mimicry and Aposematism in Butterflies? An Opposing Point of View

Abstract

AbstractBirds are universally considered to be the primary selective force leading to the evolution of mimicry in butterflies and the evolution of aposematic coloration. This concept does not take into account the visual capabilities of birds. In this paper it is argued that the aerial hawker insectivorous birds, which are the primary predators of butterflies, are not able to differentiate the separate elements in the color patterns of flying butterflies. They cannot distinguish details in color of the markings or their shape, size, and distribution. As a consequence, birds cannot serve as a selective force for evolution of mimicry and aposematic coloration in these insects. Many aspects of vision, and especially vision in birds, on which my conclusions are based are discussed in detail. The different morphological and behavioral characteristics of butterflies, especially their flight characteristics, correlate with their profitability as a source of energy and nutrients. The flight pattern of the butterfly is the first stimulus that the bird sees, not the color pattern. It is this characteristic flight pattern, not the bright aposematic coloration pattern, that birds are able to recognize and then learn rapidly to associate visually with the profitability of the prey. The characteristic flight behavior signals to the bird whether the prey is energetically profitable or not, thus whether to attack or ignore a potential prey. The ability to distinguish prey types by flight pattern allows the bird to conserve energy and maximize its feeding efficiency.