- The Himalayan rivers are increasingly threatened by habitat destruction, hydropower projects, pollution and climate change, which significantly impact the riverine birds.
- A recent study reports a decline in the populations of five riverine bird species by 5-10%, with the trends of three species matching the national bird population trends.
- Specialist riverine birds can be key indicators of river habitat quality in montane headwaters, thus contributing to the conservation of riverine biodiversity in the Indian Himalayas.
- The views in the commentary are that of the author.
The Himalayan rivers are a source to almost all the major rivers that inundate the northern plains in India. These upland rivers are amongst the most dramatic landscape features in the country. Trickling droplets from mountain glaciers form numerous streams which carve through ancient gorges and steep valleys, leaping over rock faces, cascading over boulders. The Himalayan rivers are unique.
It does not take much time for keen eyes to discover that the banks of these icy cold torrents are thriving with life too. The cascading white waters are home to feathery creatures that have adapted to these torrential mountain rivers for their survival. Unlike their colourful showy cousins who live in the forests, these birds live in extremely hostile conditions. The Himalayas harbour some of the highest diversity of specialist riverine birds.
Understanding river bird populations and habitat associations
In times of large-scale anthropogenic alterations, rivers and their riparian zones in the tropics stand among the most threatened ecosystems of the world. Rivers are the lifelines of the Himalayas, sustaining both wildlife and human communities. However, these fragile ecosystems are increasingly threatened by habitat destruction, hydropower generation, pollution, and climate change. Among the most affected and the least known are the river birds that rely on the flowing waters for food, shelter, and breeding.
A team of researchers, including the commentary author, have conducted field surveys to document riverine bird abundances convoyed by a detailed riverine habitat assessment, which bring closer attention to this obscure riverine group. The team monitored Bhagirathi river basin, an important headstream of the Ganga between 2014 and 2019, during the summer and autumn months. Repeat surveys charting the wide diversity of the riparian habitats, encompassed the major settlements of Rishikesh, Devprayag, New Tehri, Uttarkashi and Gangotri enroute the Bhagirathi river. Bird populations were estimated for 12 bird species including kingfishers, dippers, wagtails and redstarts, statistically adjusting for variation in detectability across different species in field surveys. Key riverine habitat elements such as the width of the river channel, the river flow character, elevation and riparian vegetation, influenced their numbers.
Several important facts about the Himalayan river birds and catchment characters emerged from this study enabling a clearer understanding of their importance as indicators of river ecosystems.
The occurrence of more than 31 species using riverine resources point to the fact that the Himalayan river beds are highly productive. River bird distribution reflects the condition of the riparian stretch, bringing forth the significance of the river channel character, bank morphology, aspects of river flow and land use patterns in shaping the survival strategies of these birds. Some small birds, like the brown dipper, plumbeous water redstart, white-capped redstart, little forktail, spotted forktail known as ‘songbirds’ to birders are only found along river stretches that are least modified characterised by faster flows, exposed bedrocks, banks with pebbles, boulders with more intact riverine forests. There were others, like the grey wagtail, white wagtail, river lapwing, and common sandpiper who visited riverbanks exclusively in summer to breed.
Population status of the Himalayan riverine birds
Findings from the five-year period studying river birds in the Himalayas revealed a worrying trend — five species showed population declines of 5-10% over the study period. Species such as the brown dipper and plumbeous water redstart, which depend heavily on river habitats, were particularly affected. This pattern mirrors national bird population trends, suggesting that the threats impacting the Himalayan rivers have widespread consequences for biodiversity.
However, not all species showed declines. Some birds, like the blue whistling thrush, appeared to be thriving, possibly due to their ability to adapt to changing environments. The study also found that higher elevation rivers supported more bird species, highlighting the importance of preserving these pristine habitats. River stretches affected by hydropower development did not show any signs of breeding activity in the specialist species. Dams alter the natural flow of the river creating pools that are deeper and wider and are avoided by all the river bird species that prefer clear, fast flowing river stretches. Birds nesting and feeding on riverbanks are vulnerable to loss of riparian habitats, besides the danger of nest flooding during sensitive periods of their annual cycles, such as breeding.
River birds can also be devised as key indicators of riverine ecosystem health. Their declines signal deeper problems within Himalayan rivers — problems that could eventually affect water quality, underlying prey populations of fish, aquatic and semi-aquatic insects, and even human communities that depend on these rivers.
The Himalayan river birds study design provides a blueprint for long-term riverine bird monitoring, providing the first ever systematic population count of Himalayan riverine birds which can be replicated in other mountain river systems worldwide.
Why does this matter?
In India, although rivers form significant components of inland waters they are not well protected by the law. The Indian Himalayas has one of the highest densities of proposed hydroelectric projects, proposed locations of dams correlating with zones of high species diversity. The effect of direct and indirect impacts of dams and other human modifications on riverine avifauna remains under-researched, thus hindering our ability to predict future trends. There is a dire need to put good science-based policy in the conservation of riverine ecosystems in India in place of the widely used ‘environmental flows’ as the best practice yet. It is important to look beyond the iconic species like the river dolphin, gharial and mahseer all of which are difficult and labour-intensive to monitor on the ground, to tell the tale of the ‘riverine nemesis’.
Birds specialised to live along rivers are conspicuous, popularly monitored through citizen scientist platforms, relatively easy and cost-effective to census across large spatial and temporal extents. Infrastructure for flood mitigation, irrigation, water supply and functioning of ecosystems will be an integral part of managing river systems in the Himalayas. Better management of hydropower projects, pollution control, and habitat restoration can help protect these species and the delicate ecosystems they inhabit. The conundrum between balancing our interminable needs to conserving these critical habitats, stands towering.
The author is a postdoctoral fellow at the University of Sheffield.
Citation:
- Sinha, A., Chatterjee, N., Ormerod, S. J., Adhikari, B. S., & Krishnamurthy, R. (2019). River birds as potential indicators of local-and catchment-scale influences on Himalayan river ecosystems. Ecosystems and People, 15(1), 90-101.
- Sinha, A., Chatterjee, N., Ormerod, S. J., & Krishnamurthy, R. (2025). Population variability and apparent recent decline of river birds in the Indian Himalaya. Biotropica, 57(2), e70017.
Banner image: Brown Dipper, a specialist Himalayan riverine bird. Dippers are the most studied riverine birds around the world. They are excellent indicators of water quality and riparian conditions. Image by Nilanjan Chatterjee.
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