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Himalayan birds at higher risk of losing unique traits: Study

The global extinction crisis will lead to widespread losses of morphological diversity above that expected by species loss alone

The satyr tragopan is a pheasant found across the Himalayas. Photo: iStock The satyr tragopan is a pheasant found across the Himalayas. Photo: iStock

Himalayan birds are more likely to lose traits that are unique to them than other birds inhabiting other parts of the world, a new study has estimated.

The loss of vultures might play some role in lowering the diversity in morphological traits such as beak and body size, shape, and structure in the Himalayan region, according to the findings.

Vultures, which are large-bodied and rely solely on the meat and flesh of dead or decaying organisms for food, are the most imperilled group of birds, Emma Hughes, a bird researcher at the University of Sheffield, United Kingdom, told Down To Earth.

She added that these birds fill distinct areas of morphospace, a mathematical representation that shows how diversity in bird shape and size evolves.

“Vultures provide vital ecosystem services by removing decaying carcasses, which otherwise could increase the direct transmission of infectious diseases and increase populations of opportunistic scavengers (dogs and rats) that spread rabies and bubonic plague,” she said.

Globally, birds are already facing extinction threats due to climate change. Species loss could further lower diversity in morphological traits among remaining birds, the study published in Current Biology found.

“Losing endangered species leads to species being more similar to each other in terms of their morphology,” Hughes said. Hughes and her colleagues collected data on morphological traits from museum collections of 8,455 bird species.

They used statistical modelling to determine whether extinction decreases structural diversity among remaining birds. The model predicted that loss in structural diversity could impact birds showing extreme features such as the smallest and the largest birds.

These birds are more at risk of extinction. “We find strong evidence to support the hypothesis that the largest and smallest species are likely to be most at risk of extinction,” she added.

Species threatened with extinction tend to possess more extreme trait combinations than those not at risk of extinction, the researchers speculated.

“These species are likely to be those of large body size and more specialist in their habits,” Hughes said. Specialist birds have a limited diet and can dwell in only specific habitats, according to researchers.

In forests with low morphological diversity, we might expect, on average, to see more seed-eating or generalist species that have a more ordinary beak shape and are medium to small in size, she noted. 

Mynas or house sparrows are likely to dominate. They are generalist birds, known to have a more flexible diet and can inhabit a range of habitats.

Some regions could see a greater loss in morphological features than others. “The Himalayan mountains and foothills are at particular risk and it’s likely that the loss of trait diversity will be considerable,” Hughes said.

East Asia and the moist forests of South Vietnam and Cambodia are also vulnerable, the study found.

“The global extinction crisis doesn’t just mean that we are losing species. Species extinctions will lead to a major loss of ecological strategies and functions, with important ramifications for humans as ecosystem services are lost,” Hughes said.

The global extinction crisis will lead to widespread losses of morphological diversity above that expected by species loss alone, she added.

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