Wildlife & Biodiversity

Bird species in northeastern India shifting to higher elevations, face threat of extinction

Researchers say certain bird species shifting to degraded forest systems for climate change adaptation may go extinct  

By Himanshu Nitnaware
Published: Monday 08 January 2024
Photo for representation: iStock

Bird species in northeastern India have started shifting to higher elevations due to increasing temperatures owing to deforestation, a new study showed.

A team of researchers from the Indian Institute of Science (IISc) found that above-average temperatures in the logged forests and low humidity compared to primary (undisturbed) forests is ‘hastening the transition’.

The report published in the journal Global Ecology and Evolution also noted that birds with smaller sizes colonised the logged forests better because of their ability to tolerate higher temperatures. However, the density of larger bird species appeared to be showing increasing presence in the primary forests.

The primary forest was 2.3 degrees Celsius cooler than the logged forest and 14.6 per cent more humid with low densities of foliage-dwelling arthropods, the researchers found.

“Because large species have higher absolute energy requirements, a reduction in resource availability is likely to disproportionately reduce the abundance of large species,” they noted. 

Read more: Migratory birds arrive in Odisha’s Chilika before winter; is climate change to blame?

Researchers studied montane broadleaved forest located in Eaglenest Wildlife Sanctuary of Arunachal Pradesh of the Eastern Himalayas. Tropical montane forests are unique ecosystems that can start at about 150-200 metres and reach up to 3,500 m high up on mountains around the world.

From 2011-2021, the scientists captured 6,189 individuals from 130 species. “The final analysis included 4,801 understorey insectivores — insect-eating birds that live under the canopy of large trees — belonging to about 61 species,” said Umesh Srinivasan, assistant professor at Centre for Ecological Sciences (CES) and co-author of the study.

“While the separate impacts of habitat loss and climate change on biodiversity have been studied extensively, few studies have examined the influence of both these threats together, especially in the tropics and particularly in tropical mountains,” the authors of the research noted.

The report mentioned that bird populations in the examined sites at the cold-edge limit increased survival rates over time, while the others with warm-edge elevational range limit showed declines. 

“This suggests that species are adapting to climate change by tracking favourable conditions and shifting their ranges upslope,” the researchers noted.

But we observed that individuals of the same species were unable to maintain demographic vital rates in higher-elevation logged forests in response to climate change in the long-term, said Ritobroto Chanda, former project associate at CES, IISc and corresponding author of the study.

Chanda explained that it could be attributed to the lack of resource availability in the logged forest, impacting local biodiversity and bird demographics.

Read more: Birth rate of large, migratory birds declined due to climate change: Study

Srinivasan said the study highlights the need to safeguard primary forests in order to mitigate the effects of climate change on avian populations. “Logging managers should ensure that undisturbed forests across large elevational gradients are protected,” he added.

He explained that the move will allow species to shift their ranges upwards in response to climate change and maintain survival. “If species encounter degraded forest while they shift upwards, certain species will most likely go locally extinct,” he said. 

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