Common birds endemic to Western Ghats see steep decline in past 25 years

This steep decline was worryingly found even in common species such as Crimson-backed Sunbird and Yellow-browed Bulbul.
Common birds endemic to Western Ghats see steep decline in past 25 years
Common birds endemic to Western Ghats see steep decline in past 25 years
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In what is the first comprehensive assessment of the distribution, abundance and conservation status of bird species in India, a study, titled the State of India’s Birds 2020, has found that the birds in the Western Ghats have seen a steep decline in number in the last 25 years. 

The study was conducted by collaboration between 10 research and conservation organisations within the country, spanning governmental and non-governmental institutions, including World Wide Fund for Nature India (WWF-India) and Ashoka Trust for Research in Ecology and the Environment (ATREE). They collected data uploaded by over 15,000 birders. These birdwatchers, spread across two lakh locations, uploaded data on the eBIrd India platform in Laboratory Ornithology at Cornell University. 

The analysis showed that the 12 species endemic to the Western Ghats – for whom long-term data could be found – are almost 75% lower in abundance today than the year 2000. This steep decline was worryingly found even in common species such as Crimson-backed Sunbird and Yellow-browed Bulbul.

The 12 species, taken into account for long-term analysis, were Malabar Grey Hornbill, Malabar Barbet, Malabar Parakeet, Malabar Woodshrike, White-bellied Treepie, Nilgiri Flowerpecker, Crimson-backed Sunbird, Flame-throated Bulbul, White-bellied Blue Flycatcher, Dark-fronted Babbler, Yellow-browed Bulbul and the Square-tailed Bulbul. In the last five years, however, there appears to be a stabilising trend in these species, said Ashwin Viswanathan, a researcher at the National Conservation Foundation who also worked on the report.

Half of these 12 reported a strong decline, that is, a long-term decline of over 50% and annual decline of more than 2.7%. The other half reported a moderate decline – an overall decline of more than 25%, and annual decline of more than 1.1%.

The long-term trend was measured by observing trends over 25 plus years, while the current annual trend was recorded over the past five years. Apart from these two, a third index of Distribution Range Size (i.e. how widespread the bird’s presence in India is, measured in sq km), along with the International Union of Conservation of Nature (IUCN) Red List, were used to classify 867 species of birds accounted for in the report, based on conservation concerns. The IUCN Red List was established in 1964 and is considered the world’s most comprehensive inventory of conservation status of biological species, which shows the risk of extinction.

Shrinking habitats

The Western Ghats bird species mentioned in the report were classified by their habitat. The overall pattern among habitat specialist birds (more migratory in nature) was that of substantial long-term decline.

“Of these, forest species have declined the most, followed by grassland/scrubland species, and then wetland species. Despite having greater habitat flexibility, generalist species, including Tawny-bellied Babbler and Nilgiri Flowerpecker, also show a clearly discernible decline. This indicates that there may be features other than habitat that is affecting their populations,” the study says.

The endemicity of the Western Ghats birds makes them all the more vulnerable. The study stated that many of the Western Ghats birds depend on the shola forests – tropical montane (ecosystems found in mountainous regions) forests found in valleys between rolling grasslands in the higher mountainous regions of south India, including the Western Ghats.

The species that depend on the shola forests include the Nilgiri Sholakili, White-bellied Sholakili, four laughingthrushes, two flycatchers (including the spectacular Black-and-orange Flycatcher) and the shy and little-known Nilgiri Thrush. Others like Nilgiri Pipit, Broad-tailed Grassbird and an endemic subspecies of Golden-headed Cisticola are almost entirely restricted to shola grasslands, the study says.

The Nilgiri Thrush and Nilgiri Pipit, which are significantly found in Kerala and Tamil Nadu, also showed a distribution range of “restricted” (less than 42,500 sq km), with the current trend (in the last five years) being “very restricted”, that is, less than 7,500 sq km. The Broad-tailed Grassbird – though significant in Karnataka, Kerala and Maharashtra – was also “restricted” in the distribution range index.  

What puts these species at risk is that over the past century, shola grasslands in both central and southern parts of Western Ghats have increasingly disappeared to give way to tea plantations and exotic species like Eucalyptus and wattle, which are now naturally going on to expand further into the grasslands. This has resulted in shrinking habitats for the species that depend on them.

“Aside from Palani laughingthrush, which has adapted well to fragmented habitats and tea plantations, other endemics like Nilgiri Pipit and Nilgiri Thrush show recent declining trends,” the report says.

Good news for house sparrows, peacocks

In some good news though, the Indian house sparrow, despite the perception that the numbers have been going down, was found to have stabilised. The study said that it has been fairly stable in the last 25 plus years, though there has been a gradual decline from urban centres and cities like Bengaluru, Chennai, Delhi, Hyderabad, Kolkata and Mumbai. 

“However, the extremely large range of the species across the country, and the lack of evidence for either long-term or current countrywide decline results in it being classified as of Low Conservation Concern,” the report states.

Interestingly, the Indian peafowl or peacock, which thrives in drier regions, has also seen a long-term as well as the current trend of general increase. Apart from an increase in population wherever it is present, the study postulates that the increase is a result of the species’ expansion into Kerala, where it was formerly absent.

“The reasons for this pattern have not been investigated in detail, but expansion into Kerala may be associated with an overall drying trend, and expansion into the Thar desert appears to have accompanied the spread of canals and irrigation,” the study says.

101 species in High Concern Category

Of the 867 species considered for the study, 101 were found to be in the High Conservation Concern category. High Conservation Concern is based on the distribution of the species, its ability to survive in a forest area for a period of time, its decline and abundance trends, status in the IUCN Red List and other factors. In the study, 59 species were classified into the high concern segment based on their distribution range size, and 42, by their IUCN Red List status. 

However, 26% of the species that are in the high concern category (of the study) are in ‘least concern’ classification per the IUCN Red List 2019. The ‘least concern’ tag means the species do not qualify as threatened, near threatened or dependent on conservation.

Further, seven species considered by IUCN in the ‘near threatened’ or ‘vulnerable’ were found to be of low conservation concern by the study. These are the Ferruginous Duck, Black-tailed Godwit, Woolly-necked Stork, Oriental Darter, Black-headed Ibis, Alexandrine Parakeet and Long-tailed Parakeet.

Further, the report said, “Of the 261 species, for which long-term trends could be determined (i.e. not Uncertain or Data Deficient), 52% have declined since the year 2000, with 22% declining strongly. In all, 43% of species showed a long-term trend that was stable and 5% showed an increasing trend. Only 14% show an increasing current annual trend,” it adds. 

The experts who conducted the study have called for immediate conservation action to identify causes of decline as well as measures to halt and reverse the trend for these species.

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