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The second study, also conducted by Lochan, Dinesh Kumar Sharma and Anand Kumar, who work at the Hemvati Nandan Bahuguna Garhwal University, focuses on the bird's behavioural changes. They conducted the study in two valleys in Kedarnath Musk Deer Sanctuary in Uttarakhand - at Chopta, a tourist spot with busy traffic and visitors, and the largely quiet Madmaheshwar.
They recorded more than 700 monal calls across both sites using microphones and passive recording devices and then measured pitch, call length and background noise levels for a year from April 2023.
Birds in noisy environments consistently produced calls with significantly higher peak frequencies compared with those in quieter habitats, the study said.
The researchers found subtle changes in the monal's pitch that could be picked up by recording devices but might go unnoticed by the human ear.
"This does not mean that the species has undergone a permanent or evolutionary change in its vocal frequency; rather, our findings suggest behavioural flexibility in response to different acoustic environments," Lochan said.
Compared with the birds in Madmaheshwar valley, the monal in Chopta also produced shorter call durations likely to cut through low-frequency human noise from traffic and tourist footfall.
Bird calls are one of the most sophisticated forms of sound-based communication in the natural world, and significant changes can interfere with, among other things, their mating success.
"When a species must raise its pitch to be heard over tourist traffic, or climb higher as meadows turn crowded, it reveals how human pressure is rewriting the rules of life in the Himalaya," says Anjal Prakash, a public policy professor at FLAME University and contributor to IPCC reports.
Lochan says he and his team consider this a preliminary study and hope to expand the scope and depth of it.
The research comes with the caveat that it is not conclusive on ecological consequences, and more research is needed. But together, the two studies signal broader ecological stress across the Himalayas.
"In listening to the monal, we hear the Himalayas asking for space, silence and care," says Prakash.
