Proc. Natl Acad. Sci. USA http://doi.org/rxm (2014)

Credit: © 2011 ROYAL SOCIETY

Not content to simply lure females with their vibrant plumage, many male birds of paradise undertake complex mating rituals that resemble eccentric dances (for example, see http://go.nature.com/2a1Hyk). In the case of one species, Lawes' parotia (pictured; http://doi.org/bmr3tb), the reflectance spectra of the male's feathers might be tuned to the properties of the female's colour vision — the dance is then one of complex optical stimulation, as Bodo Wilts and co-workers now report.

Colouration in the feathers of the parotia is structural — the arrangement of melanin rodlets within the feather filaments reflects light directionally, so their hue ultimately depends on the viewing angle. The silver feathers appearing on the nape of the male's neck reflect light unidirectionally. But the more complex morphology of its colourful breast feathers gives rise to 3D reflections, and feathers that can appear alternately orange, green or blue.

Wilts et al. modelled the light–matter interaction for both types of feather computationally and measured scattering patterns for comparison. A convolution of the assumed spectral sensitivities of females with the measured reflectance spectra suggested that the silver feathers activated all spectral photoreceptors simultaneously, whereas the colourful feathers selectively activated different receptors depending on the angle of incident light — providing males with a temporally variable way to dazzle potential mates.