Why are migratory birds giving India a miss?

The loss of habitats and other threats need to be countered by data-driven policy changes and aggressive monitoring to preserve their roosting sites.

A flock of northern pintail in flight as the sun rises over Nalabana Bird Sanctuary at Chilika Lake in Odisha on January 29, 2019. Over 10 lakh migratory birds visit the lake every winter. | Photo Credit: K.R. Deepak

It was a late winter evening in the early 1980s. One of us (T. Ganesh) was in a small patch of grassland near Hyderabad, counting harriers, a hawk-like bird that migrates to India in winter. There were hundreds of them, all flocking down to spend the night on the grassy meadow.

When we went back to the place some 15 years later, the grasslands had disappeared, replaced by trees planted in neat rows. The harriers were nowhere to be seen. More recently, in Tamil Nadu a large patch of grassland was lost to a tree plantation drive, robbing the harriers once again of their night roosting grounds. As we travelled across India looking for harriers, we found the same story repeated everywhere—as grasslands were diverted to other forms of use, harriers and other grassland dependent species stopped visiting. No wonder, harrier counts done by various birdwatchers and researchers across India indicated a steady decline in their numbers in the last 30 years. It is the same with many other species of migratory birds, which are rapidly losing their migratory quarters and wintering grounds.

WATCH:

Twice a year, thousands of birds migrate between their breeding and non-breeding grounds separated by thousands of kilometres. Research has found that more than half of these birds are endangered. | Video Credit: Text: Arjun Kannan, M.B. Prashanth and T. Ganesh; Visualisation by: Saatvika Radhakrishna

Twice a year, thousands of birds migrate between their breeding and non-breeding grounds separated by thousands of kilometres spanning mountains, deserts, and oceans. The long journeys are not without perils, but they still undertake it. There are examples of birds covering astounding distances while migrating. Birds like the Amur falcon, wandering albatross, Arctic terns, and the bar-tailed godwits are expert voyagers, with the latter known to undertake sea-crossings of more than 11,000 km non-stop.

The flyways

Why do birds do this? Research indicates several reasons behind the risky undertaking: the reduction in day length and temperatures in temperate regions during winter lowers food availability, making the birds move southwards to the warmer tropical regions for food. Another reason is to reduce competition with other related species.

Long-distance migratory birds have evolved to use certain flight paths for their journeys: called flyways, these span continents and oceans. A flyway includes not just migratory pathways but also breeding and wintering ranges. Broadly, there are eight migration flyways across the world. They were initially classified on the basis of the migration of the waterfowl, which journey in large flocks, but these paths are also used by other birds ranging from small songbirds (passerines) and tiny warblers to large birds of prey (raptors). Years of research that involved capturing the birds and marking them with coloured rings have helped discern these flyways. The rings have unique numerical and colour codes which help track the birds. While bird ringing has been practised for more than a century, researchers today have the option of tagging birds with transmitters and GPS loggers, which trace their migratory paths and map important stopover places, where they feed and replenish themselves.

A poster by Rohan Chakravarty for Bombay Natural History Society depicting migration journeys, ringing and recovery efforts undertaken for 25 species of birds. To the left is a map of the Indian subcontinent that shows birds ringed and recovered within India. To the right is a map of the Old World, showing rings and recoveries outside of the subcontinent. The icons that enclose the birds also depict their preferred habitat in ringing and recovery locations. The poster was displayed at the CMS COP 12 held in Manila in October 2017. | Photo Credit: BNHS/ Rohan Chakravarty 

There are three major flyways in Asia, namely the West Pacific flyway, the East Asian Australasian flyway, and the Central Asian Flyway (CAF). India falls within the CAF, which is spread across Eurasia from the Arctic Ocean to the Indian Ocean, and geographically spans 30 countries. This flyway is used by at least 400 species of birds, which breed in the central Asian region and migrate down south to the Indian subcontinent during winter. The topography and ecosystem diversity along the flyway include the high-altitude Himalayan plateau, deserts, lakes and marshes, and steppe/grassland habitats.

Long-term monitoring programmes to assess the populations of the migratory birds are still in their nascency in India, the main challenge being the large spatial scale with umpteen number of important habitats that make it difficult to monitor each of them continuously. Ecologically designed studies have been conducted only recently: before this, two decades of mid-winter waterbird counts across Asia and India were the only source of information on migratory birds. Efforts to monitor birds are more common now. In recent years, there have been several individual and group bird-watching programmes, where birdwatchers volunteer to systematically count birds at easily accessible locations (in areas close to cities). Bird Count India, an informal partnership of organisations and groups working together to increase the collective knowledge about bird distribution and population, has been instrumental in promoting small-scale monitoring programmes by individual birdwatchers.

Bleak picture

The State of India’s Birds report (SoIB), published in 2020, was the first comprehensive study on the distribution range, trends in abundance, and conservation status for most of the bird species that commonly occur in India. Based on crowd-sourced and citizen science data, uploaded in the eBird platform, the report presents a bleak picture for bird populations: 52 per cent of the 867 species assessed are on the decline. This includes long-distance migratory birds and birds associated with open ecosystems such as grasslands. For instance, species such as pallid harriers, steppe eagles and tawny eagles, all of which migrate to or within India from the central Asian steppes, are getting rarer. However, for most birds, the factors causing the decline are currently unknown.

A female Montagu’s harrier at Yenkathala grasslands near Hyderabad that has migrated from Kazakhstan. | Photo Credit: Dr. Nisarga 

This underlines the urgent need for country-wide bird monitoring and research programmes. The SoIB report pointed out that since most of the central Asian breeding regions are remote and uninhabited, much of the monitoring must be carried out in India. India can follow the example of other large countries in accomplishing this.

Europe and North America have been conducting long-term research on bird populations for almost half a century, generating valuable data. Insights from such programmes inform government policies for the conservation of birds and their habitats. Ringing programmes such as EURING have run for decades, mapping the migratory routes of more than 100 species of birds along the Eurasian-African flyways. Such programmes, strengthened by the advent of satellite telemetry, help delineate the breeding and resting sites during migration as well as the wintering sites of each species, even of individual birds. High resolution GPS trackers are now generating data at very fine spatial and temporal scales. Studies using such datasets have even been able to ascertain at which point of the migratory cycles there is a higher risk of mortality.

Bird ringing programmes have been going on in India for the last five decades. Although these programmes have provided fantastic information on large-scale migration patterns in the CAF, the proportion of ring recoveries is very low. Unless a ringed bird is captured at another site, we get no information regarding its movements. Thus for most species, we still do not have data on migration routes and breeding ranges.

Collared bar-headed geese originating from central and western Mongolia were sighted in Hadinaru lake, Mysuru, in 2017. | Photo Credit: Sighted and photographed by Vijayalakshmi Rao

Tracking technology is being increasingly used to provide information on how birds use the CAF. So, now we know about the high-altitude crossing undertaken by the bar-headed geese across the Himalaya, the long migratory flights of the Amur falcons, the loop migrations across and away from the Himalaya by the demoiselle cranes, and, more importantly, the movement and behaviour of threatened species such as the great Indian bustard and the lesser florican, which move within relatively smaller ranges in the arid part of the country. Raptors such as black-eared kites, harriers, and various species of vultures are also being tracked.

Local communities and citizen scientists have made immense contributions to long-term bird monitoring, with the collected data used for academic research. Citizen science bird monitoring initiatives launched in India in the last 10 years include the Common Bird Monitoring Programme of the Bombay Natural History Society, Bird Atlases in a few States conducted by Bird Count India, and the annual Asian water bird census that happens across all major wetlands in India. Quite often, it is a common migratory grey wagtail or a leaf warbler rather than a rarely occurring bird species that will have a story to tell.

Highlights

• Migratory birds are rapidly losing their migratory quarters and wintering grounds in India
• There are three major flyways in Asia, namely the West Pacific flyway, the East Asian Australasian flyway, and the Central Asian Flyway (CAF). India falls within the CAF.
• Long-term monitoring programmes to assess the populations of the migratory birds are still in their nascency.
• However, local communities and citizen scientists have made immense contributions to long-term bird monitoring.

Citizen efforts

Recently, the findings of a study of wintering water birds from southern Tamil Nadu spanning 10 winters was published by researchers from the Ashoka Trust for Research in Ecology and the Environment (ATREE). The study documented a decline in 28 per cent of the 50 species observed over 10 years while noting the role that large reservoirs and key wetlands along the Tamiraparani river play in the lives of wintering birds during droughts.

Birdwatchers take part in a bird and butterfly census in Salem in Tamil Nadu on February 16, 2020. In recent years, there has been a spurt in individual and group bird-watching voluntary programmes, where birdwatchers volunteer to systematically count birds at easily accessible locations (such as in areas to close to cities). The data uploaded by such programmes are invaluable for research. | Photo Credit: E. Lakshmi Narayanan 

The study was made possible by the support of citizen groups from Tirunelveli and Thoothukudi cities, as well as of student groups and volunteers across the two districts. ATREE has also started species-oriented monitoring initiatives such as the HarrierWatch programme, which not only monitors the migratory harrier populations but also collects vital information on the species’ diet through photographs and on their movements by ringing and GPS tagging them. It maps patches of grasslands across the country as well. Many more of such initiatives are enlisted in the Citizen Science India website. According to the Convention on Migratory Species (CMS), a United Nations initiative, the CAF has the least available information on migratory birds compared with the other major flyways.

Precise tracking information is available for less than 1 per cent of the bird species using the CAF. Reports indicate that a number of threats affect the birds on this route: habitat loss, prevalent practices of hunting, intensive agriculture, and lack of pesticide management. Unless more information on the migratory pathways and the network of habitats along the CAF is available, conservation programmes cannot be put in place.

Need of the hour

For this, countries along the CAF must collaborate. The CMS enacted the Central Asian Flyway Action Plan in 2020, which “provides the basis for the 30 Range States (Countries) to take individual and coordinated region-wide activities to conserve waterbirds and their habitats.”

This was followed up in a meeting (May 2 to 4) held by the Ministry of Environment, Forest and Climate Change in collaboration with the CMS in New Delhi, where range countries formalised the Central Asian Flyway initiative, agreeing to collaborate to strengthen conservation efforts for migratory birds and their habitats. The main challenge to the collection of date along the CAF are the various ongoing geopolitical conflicts and tensions in the region.

The focus of the CMS, although important, is still restricted to wetland birds and their habitats. There is an urgent need to monitor other migratory birds in the CAF as well, including eagles, falcons and songbird species that winter in key habitats across India.

Such coordinated studies are often limited by the fact that birds of forests, open habitat ecosystems and agricultural areas do not come their purview. For instance, the Raptors MoU signed by the government in 2016, aiming to promote research and monitoring of migrant and resident birds of prey, focusses on just the raptors, which, as top predators, form the flagship species. Birds lower down in the ecological chain deserve attention too.

Climate change in the course of the last few years is said to have altered the distributional ranges of birds worldwide. The need of the hour is not just to carry out research on how migratory birds along the CAF will respond to more of such unfavourable changes in the future, but also to implement policies to conserve ecosystems, which would keep the spectacular odysseys alive.

Arjun Kannan is a PhD researcher with ATREE, Bengaluru, who is working on the migration ecology of harriers in India. Prashanth M.B. studies birds in human-dominated landscapes and savanna grasslands, and works with citizen scientists to create inventories and map waterbirds. T. Ganesh is a senior fellow at ATREE.