India, Oct. 14 -- Stand on the trail above Chopta on a spring morning and you may catch it: a sharp, ringing whistle from the slope, followed by a flash of colour as a male monal bursts out of the rhododendrons. In the right light, his feathers shift from emerald to sapphire to burnished copper, as if someone had dipped him in molten metal. Locals in Garhwal have long treated the bird as part of the mountain itself. It is Uttarakhand's state bird and Nepal's national bird, and it appears in folk songs and village stories across the range.

But listen closely, and the monal in Chopta no longer sounds quite like it used to.

Singing over the traffic

Researchers at Hemvati Nandan Bahuguna Garhwal University spent a year, starting in April 2...