Washington: Until recently no one could say whether the stunning tail feathers of peacocks actually drew the eyes of peahens.
Now scientists, strapping cameras onto the heads of the female birds, have obtained evidence of what it is about peacock tails that attracts the opposite sex, the Washington Post reported.
The technology known as eye-tracking is beginning to provide answers.
Eye-tracking research has been conducted in the laboratory for more than a century. Once the necessary cameras became light enough for humans to wear, scientists conducted studies outdoors. For instance, wearable eye-trackers developed by New York-based Positive Science with funding from the US Naval Research Laboratory could be used to learn how combatants detect camouflaged targets.
For the peacock experiment, Positive Science collaborated with evolutionary biologist Jessica Yorzinski, then a graduate student at the University of California at Davis, to develop eye-trackers small enough for peahens.
Scientists from UC Davis and Duke University then rigged 12 birds with headgear equipped with two cameras - one aimed at one of the bird`s eyes, the other at the scene in front of the animal.
A wireless transmitter mounted on the bird`s back sent video from both cameras to a recorder nearby, and when those feeds were combined, a yellow dot would mark exactly where the bird`s gaze was directed.
Gradual daily training accustomed the peahens to wearing the apparatus. First, researchers fit each peahen with an empty backpack, then slowly added filler until it approximated the weight of the battery and transmitter.
Then, each bird was fitted with a soft plastic helmet. Finally, the cameras were added to the helmet, and the transmitting apparatus was put into the backpack.
In experiments, each peahen was placed alongside two peacocks in an outdoor enclosure. The males vied for attention with elaborate shows, shaking their wings and rattling their train of plumes, hooting and dashing toward peahens if the females appeared ready to mate.
The scientists weren`t surprised when they saw that the peahens looked at each peacock when it fanned its tail feathers upward. But, intriguingly, the females focused nearly completely on the bottom part of the train, close to the ground. They mostly ignored the conspicuous upper fan.
However, the peahens did pay attention to the upper feathers when the lower train was obscured - as it might be if the males were relatively far away and partially hidden by the dense vegetation of the birds` natural habitat in India.
This suggests that the flashy upper train is mostly a long-distance attraction signal, but the lower feathers are more important to close-up courtship.
The study is published in the Journal of Experimental Biology.