The male monal has distinctive green, blue and copper plumage

A sharp increase in human activity is having an impact on the way a Himalayan bird lives and communicates, two studies by Indian researchers have found.

The monal, a pheasant native to Himalayan mountain forests, is deeply woven into the region's cultural, folklore and identity. The eye-catching monal - the male has distinctive green, blue and copper feathers - is the state bird of India's Uttarakhand state and the national bird of Nepal, reflecting its cultural significance across the Himalayas.

But studies show that infrastructure development and tourism are squeezing its habitat, while increasing noise is altering how it communicates with potential mates and rivals.

Researchers from Uttarakhand conducted two separate studies over five years which flagged key threats to the bird.

One study found that the birds are forced to move higher in the mountains as their natural habitat in the alpine meadows above the tree line get crowded. The other says the monal is changing its pitch to cut through human noise in a busy valley.

"These two studies give a useful warning for other more vulnerable species - if the monal is forced to change both its voice and its address, how are the more sensitive species responding?" says Vishal Singh, an environmental practitioner working on ecology and climate issues in the Himalayas.

Dr Rajeev Lochan, lead researcher of both studies, told the BBC that they chose to study the monal as the bird has a narrow habitat range - it moves seasonally between the lower montane zone - an ecological belt found on the lower slopes of the mountains - and high-elevation alpine zones. This, he says, makes it a key indicator of ecosystem health in the north-western Himalayas.

"If the species is facing issues on this particular landscape, there might be a chance that the ecological disturbances are affecting other birds too," said Lochan.

Found high in the Himalayas, the monal lives in alpine meadows above the forests

The monal, researchers say, can be seen as a stand-in for the health of a fragile Himalayan ecosystem pushed to a tipping point due to unregulated tourism and heavy urbanisation.

While the region has always drawn tourists, trekkers and researchers given its scenic landscape and biodiversity, rapid infrastructure expansion in the past decade has made more places accessible, increasing footfall and disrupting the wildlife. This, coupled with mounting human pressures, suggests that climate change is emerging as another major threat to the region's already vulnerable biodiversity.

"There are a lot of factors at play but at a broader level, the problem is that the economic development of the region is not aligned to its ecological integrity," Singh said.

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According to the first study, climate change is projected to continue shrinking and destabilising the Himalayan monal's habitat across the Indian Himalayas through 2100 under multiple climate scenarios.

Currently, the birds are found in alpine meadows, located high in the mountains above the forests, which form some of the Himalayas' most important seasonal grazing and biodiversity-rich habitats.

The researchers modelled how climate change could shift the monal's suitable habitat across the Indian Himalayan region in the states of Uttarakhand and Himachal Pradesh. It was based on the kind of global climate models and emissions scenarios used for assessments by the Intergovernmental Panel on Climate Change (IPCC), the UN's climate science unit.

"These birds are now slowly moving upwards in the Himalayas as the snow is melting and vegetation is growing, making the area accessible to them. They are anyway being pushed upwards as their natural habitats in alpine meadows are being encroached upon by humans," Lochan said.

The model assumes that the bird needs the current climate set-up that exists in alpine meadows in the future too, a reasonable but not certain assumption.

The birds' seasonal migration may become increasingly difficult as changes in climate may force them to move to higher elevations on hills, to smaller and fragmented areas. Their population would be scattered in disconnected pockets, which reduces chances of breeding between groups and increases their risks of long-term decline or local extinction, which is already a threat, the study says.

A male Himalayan monal displays its iridescent plumage during a courtship ritual aimed at attracting a female

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.