India is a land with rich biodiversity, being one of the 17 megadiverse countries and home to 7-8% of the world's recorded species. It also houses four of the world's 34 biodiversity hotspots: the Himalayas, Indo-Burma, Western Ghats, and Sundaland. India is also home to a vast array of plant and animal life, with over 47,000 plant species and 96,000 animal species. However, unchecked development, habitat loss, and climate change have driven several species to extinction. The region’s birds, especially, are declining rapidly, necessitating urgent measures to conserve their populations.
The State of India's Birds 2023 report by a team of researchers from Nature Conservation Foundation, Bengaluru, National Centre for Biological Sciences-TIFR, Bengaluru, State of India's Birds Partnership, Indian Institute of Science (IISc), Bengaluru, Indian Institute of Science Education and Research (IISER) Tirupati, Sálim Ali Centre for Ornithology and Natural History, Coimbatore, Wildlife Institute of India, Dehradun, and Azim Premji University, Bengaluru, offers a comprehensive health check for India's avian residents, revealing critical insights into their long-term survival.
The report paints a concerning picture for many of India's bird species. Out of the 942 bird species they assessed, a staggering 204 showed significant long-term declines, and 142 continue to experience declines today. The study revealed that birds whose diets consist mainly of other vertebrates or invertebrates (like insects) have suffered the most rapid long-term declines, while those that feast on fruits and nectar have managed to remain stable. This suggests a potential link between the health of insect populations and the well-being of many bird species.
Furthermore, the report highlighted that birds specialising in grassland habitats have declined more rapidly than those in other environments, underscoring the urgent need to prioritise the conservation of India's grasslands. On a brighter note, a few species, such as the Glossy Ibis and Indian Peafowl, have shown remarkable increases in their numbers.
However, the overall trend for many iconic birds, particularly vultures, remains grim. Most vulture species in India are in a state of continued rapid decline, with the Indian Vulture showing the steepest decline. Similarly, many wetland birds, including various duck species and shorebirds, are experiencing significant declines in their populations. The study also found that migratory birds, particularly those that visit India during the winter, are declining at a faster rate than resident birds, with Arctic-breeding shorebirds being among the most severely threatened. Even some species found only in specific regions, like the Western Ghats, are facing steeper declines than other endemic or non-endemic birds.
To gather the massive amount of information and turn it into meaningful insights, the researchers turned to citizen science. Instead of relying solely on traditional, resource-intensive surveys, the researchers leveraged data uploaded by thousands of everyday birdwatchers to a platform called eBird. The platform is like a massive, collaborative digital bird-spotting diary where people record the birds they see, where they are seen, and when.
Did You Know? eBird, the citizen science platform used in this study, receives millions of bird observations every month from birdwatchers around the world, making it one of the largest biodiversity databases! |
However, this semi-structured data, collected by hobbyists who aren't always following strict scientific protocols, comes with its own set of challenges. To overcome these biases, the research team developed a SoIB Pipeline – a series of successive steps to clean, organise, and analyse the data. They started by carefully preparing the raw eBird data, removing duplicates and observations that were unsuitable. Regular calendar years were converted into migratory years (from June 1st to May 31st), which better captures the full cycle of migratory birds.
Instead of relying on reported birdwatching duration or distance, they found that list length–the number of unique species reported on a checklist–was a more reliable measure of effort. They also developed a systematic process to identify and exclude vagrant records (birds spotted far outside their usual range), ensuring that population estimates were accurate for a species' expected distribution. Critically, they implemented a rigorous review of checklist completeness, relabeling many as incomplete if they didn't meet strict criteria for thorough observation.
Once the data was cleaned, they used statistical models to estimate the frequency of reporting for each species – essentially, how likely a birdwatcher was to report a particular species given their effort and location. With this data, they looked at Long-term Change (LTC), comparing current numbers to pre-2000 levels, and Current Annual Trend (CAT) for recent changes (2015-2022). To understand how widely distributed each species was, they estimated Distribution Range Size (DRS) using an occupancy framework that accounts for birds that might be present but weren't detected. Finally, by combining these three metrics, they assigned a conservation priority status (high, moderate, or low) to each species, taking into account their global IUCN Red List status.
By creating a robust framework for analysing semi-structured citizen science data, the researchers have shown that it's possible to assess the status of a much larger number of species than previously thought. The detailed methodology, including the careful curation of eBird data, systematic removal of vagrants, spatial subsampling to reduce biases, and sophisticated statistical modelling, significantly improves the reliability of citizen science reporting, opening up new avenues for data collection.
However, the study acknowledges its limitations. Due to the nature of citizen science data, it cannot provide precise estimates of actual population sizes or detailed demographic trends (like birth and death rates), which require dedicated, long-term monitoring programs. Certain bird groups, such as nocturnal birds or mountain pheasants, are also underrepresented in citizen science data, making it more difficult to assess their trends.
Ultimately, this research provides an invaluable tool for conservation. By clearly identifying which bird species are declining, where they are declining, and why, it directly informs conservation actions and policies in India. For example, the findings on declining grassland birds can inform efforts to protect these vital ecosystems, and the insights into the decline of insect-eating birds can prompt investigations into the use of pesticides.
More importantly, this framework also serves as a blueprint for other countries in the Global South with active birdwatching communities but limited resources for traditional surveys, enabling them to conduct their own State of Birds assessments. By integrating these regional findings with global conservation efforts, the study can even influence international conservation priorities, such as the IUCN Red List status of migratory birds that span continents. In essence, this collaborative, data-driven approach empowers both scientists and citizens to work together to safeguard India's incredible avian diversity for future generations.
This article was written with the help of generative AI and edited by an editor at Research Matters