Magazine article Natural History

Ol' Blue Eyes

Magazine article Natural History

Ol' Blue Eyes

Article excerpt

Peacock tail feathers, with their iridescent, multicolored eyespots, have long fascinated scientists. They vexed but also inspired Charles Darwin while he was formulating his theory of sexual selection, and they certainly catch peahens' attention during male courtship displays. But how exactly do eyespots affect males' success with the females?

Known as ocelli, the eyespots have a purple-black center surrounded by a blue-green ring and an outer bronze-gold ring. Those colors arise as light is refracted through a complex nanostructure of keratin and melanin inside the hairlike barbules that make up each ocellus. Behavioral ecologists Roslyn Dakin and Robert Montgomerie from Queen's University in Ontario, Canada, wondered whether the most successful males differed from other males in some aspect of their coloration.

The team captured and banded birds in three feral, park-dwelling North American populations. To compare the size and coloration of the ocelli in different birds, they clipped off the eyespots from the five longest feathers in each male's train. Choosing one feather per bird, they used a spectrometer inside a darkroom to calculate thirty-six color variables for each eyespot color patch, taking into account the angles of incident light that would strike feathers as males display facing females, the known sensitivity of the peafowl eye, and the various components of color such as hue, saturation, and brightness. Displaying males were also photographed to count the number of eyespots in their trains, which ranged from 127 to 162. …

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