Raptors such as the short-toed snake eagle (Circaetus gallicus) are under threat in India.Credit: David Allemand/Nature Picture Library

Hundreds of bird species in India are in decline, according to the country’s first major report on the state of bird populations. Birds of prey and waterbirds seem to have been hit particularly hard owing to habitat destruction, hunting and the pet trade.

But it’s not all bad news. Species such as the house sparrow seem to be doing better than previously thought.

The State of India’s Birds report, released on 17 February, relied on more than 10 million observations from birdwatchers recorded in the online repository of worldwide bird sightings, eBird.

The report’s authors — researchers from 10 government and non-profit research and conservation groups — used eBird data to analyse long-term trends for 261 bird species. That is, the proportional change in the frequency of reported sightings of since 1993. They found that more than half of those species have declined since 2000. The group also looked at the current annual trends in 146 species; nearly 80% have declined in the past 5 years.

The researchers classified 101 species as of high conservation concern, and another 319 species as of moderate conservation concern, on the basis of declines in their abundance and range, and their status on the International Union for Conservation of Nature’s Red List.

Populations of several raptors, including species of eagles and harrier, have decreased, but vultures most severely. Of the nine species of vulture found in India, seven have been declining in numbers since the early 1990s, largely because of poisoning by the livestock anti-inflammatory drug diclofenac. “The extent of decline in raptor population is very alarming,” says Farah Ishtiaq, who studies avian diseases at the Tata Institute for Genetics and Society in Bengaluru, India.

Numbers of migratory shorebirds, including species of sandpipers, gulls and plovers, have declined most strongly among waterbirds in the long term, the report found, although many resident species of ducks, geese and terns also show sharp declines.

Populations of the yellow-crowned woodpecker (Leiopicus mahrattensis) are in decline in India.Credit: Kane Lew/Shutterstock

Despite the gloom, sightings of the country’s national bird, the Indian peafowl, have increased, and the species seems to be expanding its range. The common house sparrow, which was presumed to be in decline, still shows a downward trend in the big cities in India, such as Bengaluru, Delhi and Mumbai, but across the country, its population seems stable.

"The strength of this effort is that it provides perhaps the first India-wide assessment of trends in bird populations. This is a remarkable achievement," says V. V. Robin, an evolutionary ecologist at the Indian Institute of Science Education and Research in Tirupati.

Although the volume of data being collected by citizen scientists on eBird is massive, historical data on many Indian birds are lacking, and current data on some very restricted, endemic species is insufficient to understand their status, says Robin. There is very little citizen-science data, historic and present, for species such as the white-bellied sholakili (Myiomela albiventris), which lives on a mountaintop that not many people visit, he says.

Robin says that for some species, conventional, long-term field research is needed, rather than only data from citizen birdwatchers.