Simultaneous Crypsis and Conspicuousness in Color Patterns: Comparative Analysis of a Neotropical Rainforest Bird Community

Abstract

Understanding how animals achieve simultaneous conspicuousness to intended receivers and crypsis to unintended receivers requires investigating the distribution, size, and spectral characteristics of color patches. Here we characterize plumage patterns of 40 rainforest bird species living in understory or canopy. Visual signals maximizing (or minimizing) detection are expected to differ between these contrasted light habitats, making rainforests appropriate to test hypotheses of color signal evolution. Using spectrometry and comparative analyses, we show that canopy and understory act as distinct selective regimes that strongly influence bird coloration. Birds reduce detectability by displaying countershaded patterns, by matching background color and contrast, and by reducing in size the most conspicuous patches. More intense on males than on females, selection for conspicuousness acts on large patches by increasing contrast on ventral parts likely to be seen by conspecifics. It also operates on small patches by focusing visual contrast on chest, head, and tail in understory and on wing and tail in canopy, by increasing local brightness contrast compared to general contrast in canopy, and by exploiting different wavelengths for contrast (short in canopy and long in understory). These results are of general interest to understanding the evolution of color patterns for all organisms living in contrasted light environments.

Keywords: color pattern; countershading; light environment; signal evolution; visual communication.