New Delhi, Feb 19 (IANS): The birders in Delhi-NCR, as well as across India, are keenly awaiting the annual 'Big Bird Day' on Sunday, when they spend the entire day bird watching and recording the number of species sighted.

The Big Bird Day was initially started by the DelhiBird group, created by Nikhil Devasar and Bikram Grewal, as an informal event to be held in February or March. The first Big Bird Day was held on February 22, 2004, when 236 species of birds were spotted across Delhi.

In 2021, 244 species were recorded, 253 in in 2020, 247 in 2019, and 237 in 2018.

"Over the last 20 years, the number of bird watchers has increased exponentially. As a result of that, the number of species that are sighted has increased. But overall, the number of birds is going down," Devasar told IANS.

There were barely 15 birders in Delhi 20 years ago, and less than 100 in the whole country.

"Today, Delhi alone has 25,000 birders," he claimed.

The Big Bird Day is also observed by birders across India now. Self-organised volunteer birders under the guidance of chosen group leader(s) cover the fields and wetlands from early morning until late in the day to spot bird species.

Over the years, the data collected has revealed the changing trends in habitat condition, bird diversity, migration and related ecological issues.

A variety of factors have contributed to the decline in the number of birds found in and around Delhi, loss of habitat being the foremost.

Yamuna's increasing filth over the decades too is among the reasons, as Delhi's birders used to easily count about 30,000 ducks in winters earlier; now the numbers are less than 10,000.

"The number of sparrows has also gone down as the modern buildings do not have chajja/niches where these sparrows used to build their nests," he said.

In 2013, the Big Bird Day went truly national with over 160 teams comprising over 1,000 birders coming together to celebrate the first pan-India Big Bird Day. In 2017, six international teams participated in the Big Bird Day.