Dwindling Bird Populations are an Indication of Biodiversity Loss

A majority of bird species in India are on the decline – an alarming indication of biodiversity loss and anthropogenic pressures on the environment, a new report assessing bird diversity and population stability in the country has found.

Birds perform a number of important ecosystem services, aiding in seed dispersal and pollination, as well as acting as predators and scavengers. But around 60 percent of birds assessed in the report have declined over the long term of 30 years, which conservationists have termed a matter of deep concern. Around 40 percent were found to be declining currently, over the last eight years.

“It’s a two way link. The number of declines could be because of declining ecosystem functioning, or resource availability, or habitat decline itself. But one can also imagine consequences in the other direction. The decline in raptors, for example, could result in changes in populations of rodent communities, which may see a boom,” said Ashwin Viswanathan, Research Associate at the Nature Conservation Foundation, one of the organisations that contributed to the assessment. “A lot of this is speculation. We need to find out how ecosystems are adapting to changing bird numbers,” he added.

The findings were captured in the State of India’s Birds 2023 report, which was released August 25 by a consortium of 13 government and non-profit conservation organizations, and based on 30 million bird sightings. The report identifies 178 birds of high conservation priority which need urgent action plans for their conservation and deeper research to understand the factors leading to their decline. Some of these species include the sarus crane, the Indian courser, the Andaman serpent eagle, and the Nilgiri laughingthrush.

Habitat ‘specialists’ are especially vulnerable, while ‘generalists,’ or birds that have adapted to a variety of landscapes, have been stable in comparison. Some species, like the ashy prinia, rock pigeon, Asian koel, and Indian peafowl “have increased dramatically,” over the years the report finds.

Overall, however, the results are grim and call for a re-classification of 14 species by the International Union for Conservation of Nature (IUCN) to its Red List of threatened species.

Birds in open habitats particularly vulnerable

The report released last week is the second edition of the SoIB, the first of which was released in 2020. The latest report assesses 942 bird species, up from 867 in 2020, and was based on 30 million sightings recorded on the eBird portal by 30,000 citizen birdwatchers. Such citizen science “which may be less or more coordinated, is the only way in which information can be generated for biodiversity assessments at the required scale,” the report says.

“We were surprised to see that, even with a more robust statistical analysis, more data, and more observations than last time, bird populations are declining. This indicates its a more serious problem that we previously realised,” said Rajah Jayapal, a senior scientist with the Sálim Ali Centre for Ornithology and Natural History (SACON), which also contributed to the report.

The declining trajectory of bird populations in India follows global trends, where 48 percent of birds have declined, according to the 2022 State of World’s Birds report. India hosts around 1,350 of the world’s bird species, of which 78 are found only within India.

Birds inhabit all kinds of ecosystems, from coasts and wetlands to high altitudes and tropical rainforests. But birds that occupy open natural ecosystems (ONEs), particularly grasslands and semi-arid landscapes, are especially vulnerable, with such species declining by 50 percent, the report says.

A well known example is the great Indian bustard, which is on the brink of extinction because of land use changes and habitat loss. But there are other species that are seeing steep declines too. “Of particular note is great grey shrike, because it has suffered a particularly worrisome long-term decline of more than 80%. This species and other grassland specialists like chestnut-bellied sandgrouse have done better in regions rich in ONEs compared to the country as a whole, indicating the importance of conserving ONEs,” the report says.

Birds that live in wetlands as well as in wooded areas, such as forests and plantations, have also declined more than generalist species, “indicating a need to conserve natural forest habitats so that they provide habitat to specialists.”

Birds feed on a variety of sources, such as meat (vultures and other raptors), fruits and nectar (barbets and sunbirds), seeds (sparrows and doves), and invertebrates (warblers and flycatchers). Bird populations could also be influenced by limited or contaminated food resources.

“In India, birds that feed on vertebrates and carrion have declined the most, suggesting that this food resource either contains harmful pollutants or is declining in availability, or both. Strong evidence from other countries shows that agrochemicals lower survival rates in some raptors,” the report says, adding, “We find that birds that feed on invertebrates (including insects) are declining rapidly. This needs to be taken together with recent findings that insect populations worldwide have reduced, and that pesticides are thought to be a main contributor to massive declines in European insectivorous birds.”

Over 40 percent of the world’s insect population has been on the decline and is likely to go extinct in the coming years. Scientists in India suspect similar trends are playing out here, but data is limited.

Fruit and nectar feeding birds are doing well, “maybe because these resources are readily available even in heavy-modified rural and urban landscapes,” the study says.

The report also notes the widespread decline of both resident and migratory ducks, but says there is little understanding of why this otherwise flocking species is reducing in number. “One of the main recommendations is to support research as much as possible, because the data leaves us with so many unanswered questions. We know certain birds and groups of birds are declining, and we now have information to focus research into why,” said Viswanathan.

Threats and recommendations

Even though India has Protected Areas and laws like the Wildlife Protection Act, which awards special protection for certain species, these measures are not sufficient to stop the declining populations of birds in India, whose ranges span from hundreds to thousands of kilometers.

The report locates declining bird populations within eight broad threats, such as environmental pollutants, forest degradation, urbanisation, avian disease, illegal hunting and trade and climate change. The spread of monocultures through commercial plantations or afforestation programmes have reduced biodiversity. “Plantations lack vertical and horizontal vegetation complexity because they maintain even-aged stands of a single tree species for ease of harvest. This usually leads to loss of large-sized trees and reduction in canopy shade and shrubbery,” says the report. The result is fewer bird species occupying these areas compared to rainforest habitats.

Another threat is the expansion of renewable energy infrastructure, such as wind mills. Rotating wind turbines can result in fatal collisions, displacement, or barriers to migration for birds. According to the report, 60 species from 33 families of birds are affected by collisions and electrocution at power lines in India.

“Open habitats are the ones which are immediately available for infrastructure, developmental, and renewable energy projects,” said Jayapal. The report comes at a time when India is rapidly expanding renewable energy and changing its forest policies to accommodate more plantations, while granting more exceptions for the diversion of virgin forests.

“In the face of diverse developmental pressures, maintaining the size and integrity of natural habitats is crucial. Beyond this, where habitats have degraded over time, restoration efforts will be vital: not planting trees in monocultures, but rather ecological restoration of multiple habitats including non- forest habitats like grasslands,” says the report, adding, “One particular challenge will be to mitigate the considerable negative effects of even small-scale infrastructure such as wind energy, often thought of as ‘green energy’.”

Some of the recommendations made by the report include conducting “targeted, systematic, periodic monitoring of bird populations, using consistent methods, over long periods of time. Moreover, monitoring changes in other factors such as disturbance, climate, and land-use is also crucial to building a deeper understanding.”

In 2020, the Indian government announced a 10 year Visionary Protection Plan for the conservation of avian diversity, ecosystems, habitats and landscapes. The Plan outlined steps to be taken in the near, middle, and long term to effectively monitor and raise awareness about bird conservation. The SACON is one of the focal institutes supporting the VPP. According to Jayapal, 17 states and union territories have initiated work on their own VPPs, while five — Uttarakhand, Delhi, Telangana, Andhra Pradesh, and Meghalaya — have completed the process. “By 2030, we expect states to pay more attention to bird conservation issues and work to mitigate priority areas,” he said.

Says Viswanathan, “The amended Wildlife Protection Act took into consideration some of the findings from the SoIB 2020 report, and so we’re hopeful that some policy interventions will follow this one. We’re hopeful that a simple intervention, like recognising open landscapes as open, and not allowing plantation and afforestation activities there will be done.”

This story was first published on Mongabay India