Fig. 5.

Visibility in the dancing ritual and spectral tuning. (A) A female Western parotia, a close relative of Lawes’ parotia, observing from an elevated position the ballerina dance of a possibly interesting male (photo courtesy of Tim Laman). (B) Spectral sensitivities of the four photoreceptors of the pigeon peaking in the violet, blue, green, and red, respectively (after ref. 25). (C and D) Normalized integrated signals in each photoreceptor channel for the angle-dependent spectra of the occipital (C) and breast (D) feather, calculated by multiplying the barbule reflectance spectra (Figs. 2 and 3) with the photoreceptor spectral sensitivities. Each feather type has a unique optical signature, particularly important in the dancing ritual of the male bird-of-paradise (see Biological Implications and Connection to Bird Vision for details).