Plumage no sacrifice for peacocks

Peacocks are known for their long iridescent feathers which they use to attract a mate, but their display of love was also thought to be a sacrifice as it affected escape from predators. Not so say scientists from the University of Leeds, who filmed five Indian peacocks taking off using two high speed cameras to determine what price males pay for their attractive plumage. “These feathers can weigh about 300g and can exceed 1.5m so it is expected that the male birds would be making significant sacrifice in their flight performance for being attractive – possibly giving up their lives if the train restricts escape from predators such as tigers and leopards in their natural environment,” said Dr Graham Askew from the School of Biomedical Sciences. The same birds were filmed in 3D with and without their full plumage. Their feathers, which moult at the end of the breeding season, were cropped so allow scientists to judge the change in take-off performance between the two states. Scientists recorded the position of each bird’s centre of mass, wing motions and movement of the train in take-off before calculating the amount of power used by the birds to accelerate and gain height over the first two wing beats. Results, published in the Journal of Experimental Biology, were essentially the same – there was no difference whether the train was present or not. “Intuitively you expect that the train would detrimentally affect flight performance and so not finding a detectable effect was a bit surprising,” Askew said. “These birds do not seem to be making quite the sacrifices to look attractive we thought they were.” “The train of the peacock is one of the most iconic examples of sexual selection in the animal kingdom. It has been though that such elaborate ornamentation carries a functional cost for the bearer,” Askew added. “These results therefore have broader ramifications for evolutionary biology’s understanding of sexual selection.” Scientists also studied how much drag the train created by mounting a detached train in a wind tunnel. Although drag doubled, birds only used a small amount of power to overcome it, therefore the impact of the feathers during take-off is negligible. But Askew said there are some disadvantages; the train might adversely affect flight stability or the  ability to run. Even creating the plumage is costly, with males investing 3% of their daily metabolic energy to train growth. The elaborate plumage in peacocks is not such a drag