A team of researchers from the Indian Institute of Science (IISc), Bengaluru, conducted the study in the Eastern Himalayas' Eaglenest Wildlife Sanctuary in Arunachal Pradesh over a period of 10 years, from 2011 to 2021. The research focused on insectivorous birds in the understorey regions below the forest canopies.
Key threats identified
The researchers found that avian species in the Himalayan regions are under threat due to habitat degradation. Anthropogenic changes were noted as threatening the survival of these avian species. Logged forests were consistently hotter and drier during the day and colder at night compared to primary forests, exposing birds to stressful fluctuations due to loss of forest canopy.
These conditions could intensify with climate change in the Eastern Himalayas, where bird species are thermal specialists uniquely adapted to stable climates.
Methodology and data collection
Scientists from the Centre for Ecological Sciences (CES) at IISc examined how changes in forest microclimates influenced the survival of wild bird populations.
They used a mark-recapture dataset, tagging birds with lightweight aluminium rings and revisiting the same sites annually to track survival and changes in body mass. This was paired with temperature-humidity loggers placed in both primary and logged forests to assess how insectivorous birds adapt to microclimatic changes.
“Using these long-term data sets, we can better understand why some species survive after logging while others decline strongly,” said Akshay Bharadwaj, co-author of the study.
The study, titled "Microclimatic niche shifts predict long-term survival and body mass declines in a warmer and more degraded world", was published on November 11, in the British Ecological Society Journal, under the open access publishing success: a guide for authors category.
Underlying mechanisms and global context
The report noted that while tropical species worldwide are exposed to and respond to the synergistic impacts of multiple global change drivers, such as climate change and habitat degradation, the underlying mechanisms shaping species' demographic and phenotypic responses to anthropogenic changes remained poorly understood.
“Species that can still find microclimates in logged forests similar to their original forest homes are surviving after selective logging. It is those which cannot match their old conditions that face steep declines,” Bharadwaj said.
Conservation recommendations
Based on the findings, the researchers suggested that conservation strategies should prioritise preserving primary forest across elevational gradients. In degraded areas, microclimatic remediation could be considered, such as creating shade covers or supplementing water sources to mimic original microhabitats and support vulnerable species.
“The impacts of forest degradation will impact food chains that are part of larger ecosystem processes. A drop in the number of insectivorous birds can lead to an increase in insect numbers, which in turn can affect ecological stability," the report pointed.
