Differences in color vision make passerines less conspicuous in the eyes of their predators - PubMed (original) (raw)

Comparative Study

. 2005 May 3;102(18):6391-4.

doi: 10.1073/pnas.0409228102. Epub 2005 Apr 25.

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Comparative Study

Differences in color vision make passerines less conspicuous in the eyes of their predators

Olle Håstad et al. Proc Natl Acad Sci U S A. 2005.

Abstract

Sexual selection often favors brighter and exaggerated traits, which also increase the risk of detection by predators. Signals that are preferentially conspicuous to conspecifics would reduce the predation cost of signaling and, therefore, might facilitate the evolution of stronger sexual and social signals. This selective signaling is possible if predators and prey have differently tuned sensory systems. By using a retinal model to compare reflectance from the plumages of Swedish songbirds to the reflectance of their natural backgrounds, we found their color badges to be significantly more conspicuous to other songbirds (which have a UV-tuned visual system) than to raptors and corvids (which have a violet-tuned system) in both coniferous and deciduous forests, consistent with an adaptive private communication system.

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Figures

Fig. 1.

Fig. 1.

Average ambient light in the middle of foliage of sun-exposed trees. The solid line indicates coniferous forest, and the dashed line indicates deciduous forest.

Fig. 2.

Fig. 2.

Differences in the visibility of songbird plumage colors when viewed by another songbird or an avian predator against coniferous (A and B) or deciduous (C and D) forest backgrounds. Pc, blue tit (P. caeruleus) yellow chest (see Fig. 3); x, colors differing <2 σ from the background (excluded from analysis). Solid line indicates equal distances from the background for both vision systems. Points below the line are more different from the background to songbirds than to their predators. Box plots show medians and quartiles, and the whiskers show the most extreme data points but no more than 1.5 times the interquartile range from the box.

Fig. 3.

Fig. 3.

Spectrogram of a blue tit's yellow chest (Fig. 2_D_, point Pc), an example of a color that is cryptic to avian predators but conspicuous to songbirds.

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