Commentary

Why bird decline in India should worry all of us

Dipping avian populations are a direct indicator of environmental degradation.

Abdul Jamil Urfi*

doi:10.1038/nindia.2020.34 Published online 20 February 2020

When bird populations go down, they indicate imbalances in our immediate environment.

© S. Priyadarshini

What is the status of biodiversity in the face of deteriorating environment — this is an important question, not just for conservationists but also for policy makers and planners. The findings of a report The State of India’s Birds 2020 published this week (17 February 2020) at the 13th Conference of Parties to the Convention on Migratory Species held at Gandhinagar, Gujarat, India demonstrate once again how valuable birds are as pointers towards an all-round degrading environment.

Broad trends

The report indicates that while 48 per cent of common bird species of India have remained stable or increased in the long term, 79 per cent have been on decline in the last five years. In all, 101 species have been classified as of 'high conservation concern'. The species which appear to have suffered the highest declines in the past quarter century are the White-rumped Vulture, Richard's Pipit, Indian Vulture, Large-billed Leaf Warbler, Pacific Golden Plover and the Curlew Sandpiper. Some of these are globally threatened species.

Interestingly, the species which have increased the most in the same period are Rosy Starling, Feral Pigeon, Glossy Ibis, Plain Prinia, Ashy Prinia and Indian Peafowl. Raptors, migratory shorebirds, and species endemic to the Western Ghats have also declined considerably. Common species like Small Minivet, Common Greenshank and Oriental Skylark have declined. Birds that eat invertebrates have declined as a group.

The analysis throws up some surprises too, one of which concerns the House Sparrow, numbers of which were believed to be declining at an alarming rate. A number of factors such as changes in housing styles in urban and rural areas and in their environment, including radiation discharge from mobile phone towers, were suspected to be responsible for this though no study has ever managed to demonstrate conclusively any cause-effect relationship between the two (or for that matter, the suspected decline). However, this study shows that House Sparrow populations seem to be roughly stable across the country as a whole, though in the major cities a declining trend is observed. Species close to our hearts, like the Indian Peafowl, seem to be doing well.

Populations of the House Sparrow are believed to be declining at an alarming rate.

© Ritika Mukherji

Some globally ‘near threatened’ species, including Black-headed Ibis and Oriental Darter, have stable or increasing populations and therefore are classified as of ‘low conservation concern for India’.

Flight ahead

Though falling short of offering conservation solutions for each specific case, the report has plenty of food for thought to ponder over what is happening to our immediate environment and how different species of birds are responding to it. 

There are some important suggestions for researchers and policy makers. Not all of them are new or unique as they have been floating around for a while. The broad suggestions include promoting collaborations between researchers and the public at large, initiation of efforts to better understand neglected species, investigating reasons for decline, filling information gaps in areas with less bird watching, and initiation of more regional monitoring efforts. 

Crowd sourced science

The huge effort to map India's bird populations is an outcome of  a collaborative venture of ornithologists affiliated to ten Indian research and conservation organizations, both governmental and non-governmental (Ashoka Trust for Research in Ecology and the Environment (ATREE), Bombay Natural History Society (BNHS), Foundation for Ecological Security (FES), National Biodiversity Authority (NBA), National Centre for Biological Sciences (NCBS-TIFR), Nature Conservation Foundation (NCF), Sálim Ali Centre for Ornithology and Natural History (SACON), Wetlands International South Asia (WI-SA), Wildlife Institute of India (WII) and World Wide Fund for Nature India (WWF-India). The report is among one of the most rigorous exercises to assess the status of the common birds of India, using innovative methods and a unique data base.

Species such as the feral pigeon have seen an increase in numbers.

© S. Priyadarshini

Typically, conservation monitoring exercises of this nature require data across large spatial and temporal scales. Structured countrywide programmes involve monitoring for different species in various habitats by volunteers in the field. Though highly desirable, such exercises can prove to be costly, time consuming and overbearing, and so it is easier and practical to use alternate data sets — those generated by crowd sourced methods.  Birds are convenient and easy to monitor this way because of their immense popularity, as witnessed by the involvement of birdwatchers in all manner of bird recording programmes in recent years in India.

Indian birdwatchers have in the past participated in a structured countrywide programmes of counting waterbirds, the Asian Waterfowl Census (AWC), operational since 1987. The State of India’s Birds 2020 report makes use of a semi-structured program known as eBird. Managed by the Cornell Lab of Ornithology eBird began with a simple idea — that every birdwatcher has unique knowledge and experience. It gathers this information in the form of checklists of birds, archives and curates it, and shares it freely to power new data-driven approaches to science, conservation and education. 

Currently, eBird is the world’s largest biodiversity-related citizen science project, with more than 100 million bird sightings contributed each year by eBirders around the world. In India, many birdwatchers began to use this platform in a concerted manner in 2014 for uploading their observations.

Rigorous methodology

The report used a diligent method to analyse data. The population status of each species of bird was measured against three indices: 1) long-term trend, percentage change in frequency of reporting in 2018 when compared to pre-year-2000 levels; 2) current annual trend, mean percentage annual change in frequency of reporting in the last 5 years, from 2014 to 2018 and; 3) occupied range size in the last 5 years, 2014 to 2018.

Birdwatchers, while out in the field made checklists of species seen in a particular locality. Each checklist contained extremely valuable information, such as date (which gives an idea of season), place (from which geographical coordinates can be extracted) and presence or absence information about a given species. 

The report assesses the status of 867 Indian birds using the massive database of information contributed over 15,000 by birdwatchers on e-bird. The team of ornithologists who drafted this report used a number of filters (for instance, excluding all records not marked for public output, all pelagic checklists (outside the Indian land boundary), all checklists with specified travel distance greater than 50 km) and marked all species occurrences in standard grids (such as 100x100 km, 50x50 km). 

Population status indices for each species were developed and the report discusses the mechanisms to minimize the influence of sampling bias in considerable detail. A number of parameters for each species such as observed range sizes, trends and occupancy were calculated. All usable data from checklists were placed into ten time-periods (10 temporal bins or time intervals) to analyse the trends.

The last major effort to document and collate conservation related information on Indian birds was the publication of reports on Important  Bird Areas (IBA) of India, an collaborative exercise between BNHS and several international agencies. This new report, based on a rigorous method of data analysis, is a significant next step.

(*The author is an Associate Professor in the Department of Environmental Studies, University of Delhi.)