干旱区生态环境知识资源中心

The evolution of egg mimicry by parasites and the recognition of foreign eggs by hosts are important components of the coevolutionary arms race between brood parasites and their hosts, which is one of the most behaviorally complex of all host-parasite interactions. To examine cues used by the Yellow Warbler (Setophaga petechia), a non-ejecter that buries or deserts eggs laid by parasitic Brown-headed Cowbirds (Molothrus ater), we added model eggs of different sizes and colors to nests. We also reviewed the literature to investigate the effects of model egg surface color (background and maculation) and size on the response of hosts that eject. We predicted that size would be more important for Yellow Warblers as they likely use tactile cues to bury or desert parasitized clutches and color cannot be assessed tactilely. In Yellow Warblers, rejection frequency increased as size and color diverged more from real warbler eggs. Egg size was not generally used as a criterion for egg rejection, however, across different species that eject parasitic eggs. Color was the only model egg parameter, out of color and size, that significantly affected rejection in these ejecter hosts. Tactile cues are therefore not used by ejecters but are more important in a host that uses methods of rejection that do not require egg discrimination, such as burial and desertion. Of metrics that took into account the ultraviolet range, achromatic Just Noticeable Differences (brightness) in Yellow Warblers better predicted rejection of model eggs based on color than chromatic Just Noticeable Differences (hue). The high costs of burial and desertion may have led to multiple (size and color) egg discrimination abilities in the Yellow Warbler.