Vanishing chirps: Rapid urban growth pushes Bengaluru’s birds to the brink

Not too long ago, Bengalureans woke up to the chirping of sparrows or the plaintive call of the koel. Today, the honking of vehicles has replaced it. The city's rapid growth has taken a toll on biodiversity, particularly on birds.

Birds have always called our city home, especially in the early 80s and 90s, when the city was still known as a pensioners' paradise. The Annotated Checklist of the Birds of Bangalore, compiled in 1994, documents the presence of nearly 340 species within a 50 km radius of the city.

The list compiled by the Birdwatchers' Field Club of Bangalore included species such as the Barred Jungle Owlet (Glaucidium radiatum), reported from areas including Rajajinagar in 1979 and Doresanipalya in 1986. Today, this species is likely found only in patches of forest in Bannerghatta National Park or in other wooded areas on the fringes of the city.

The Lesser Florican (Sypheotides indicus), which was presumed extinct since 1911, was surprisingly resighted in 2012, at Hesaraghatta and has never been sighted since. The Malabar Whistling Thrush (Myophonus horsfieldii), regularly seen in the Nandi hills, was observed on the GKVK campus in early 1996 and has recently appeared on the IISc campus.

Researchers from Azim Premji University and the Nature Conservation Foundation used eBird data and examined the frequency of bird reports across the city. Using a subset of 67 aquatic species over five years, they found a drastic decline in reports of migratory birds and an increase in the number of resident birds. Species such as the Northern Pintail (Anas acuta), which were common in wetlands like Hebbal around 2010, declined sharply, while resident birds, such as Painted storks (Mycteria leucocephala), increased.

Indian grey hornbill a native bird seen in Bengaluru. Photo courtesy: Seshadri K S

These are just examples of how Bengaluru’s ecology changed during development. The biodiversity in the garden city’s natural areas is now either pushed out or has vanished.

However, birds have also tried to adapt to Bengaluru. The landscape, once largely open, has transitioned to densely planted areas, gardens, parks, and institutional campuses. New layouts that emerged across the city included home gardens, which continued to support bird life. The birdlife in the city has therefore persisted in the sea of buildings.

City’s toxic soup bowls

Platforms such as eBird, which collate data from birdwatchers, show there are 391 bird species in Bengaluru. Over the last year, 305 of those have been sighted. In a 2021 study, researchers examined how the waterbird population varied across the city. Larger wetlands supported larger populations, also because they offered better resources for food or refuge. But these were far from the city centre. What happened to the ones inside the city is a sad story.

Historically, wetlands would retain water during rain. But many wetlands within the city limits have been shrunk, built over, or converted into treated sewage storage pits, which we call lakes. In a quest to develop blue-green infrastructure, the city administrators resort to deepening the wetland, raising the bund, creating a walking track around it, and pitching the embankments with stones.

A soup-bowl design significantly changes the natural structure of a wetland. Pintail ducks would occupy the deeper water, while wading birds — such as sandpipers and stilts —would forage along the shallow edges. This cannot happen with a soup bowl design. The increase in resident species, such as painted storks, is primarily due to habitat modification. By removing areas essential to other birds and introducing fish stocks, the conditions start to favour only certain species.

The vegetation around the wetlands is also extensively modified through the planting of exotic trees or the creation of dense “Miyawaki” forests — mostly a homogenised population of trees in place of multi-layered vegetation, such as grass, herbs, shrubs, and trees. This removes specific nesting places and food sources for some birds. Even in parks, we see only trees and not many shrubs or bushes.

Pied Kingfisher seen in Hesaraghatta. Photo courtesy: Seshadri K S

When heat kills habitats

Cities are getting hotter. Heat extremes are particularly severe in densely built-up areas, where buildings retain heat, raising surface temperatures. Heat extremes are uncomfortable not just for humans but also for birds. Temperatures in and around the wetlands and parks are much cooler than in areas closer to buildings.

Earlier this year, researchers from the Indian Institute of Human Settlements used eight years of eBird data to examine how urban heat may be shaping the distribution of birds. They used data on 19 bird species and found that, in general, hotter parts of the city were likely to have fewer species.

Much of the variation in the associations they observed is attributed to the habitats these birds use and their dependence on resources such as tree holes and open areas.

“The landscape design in urban areas is repetitive,” explains avid birdwatcher Prashanth M B. “As a consequence, the bird composition will be dominated by generalist species, and specialists will decline.”

He feels cumulative species lists are poor indicators of diversity. Citizen-sourced data has limitations because some areas are visited more often than others.

The continued absence of a robust monitoring framework is a missed opportunity for Bengaluru. While interest in birdwatching has certainly grown over the years, birdwatchers now need to travel farther from the city. Most areas of the city are gentrified, and there are rarely any birds.

Ironically, researchers rely on data gathered by birdwatchers. The birdwatching community in Bengaluru is an essential watchdog and whistleblower of the damage done to natural habitats in and around the city.

Many collective efforts by birdwatchers have protected natural areas and stopped habitat destruction. Some birdwatchers have also started initiatives to install nest boxes in green spaces and to advocate for the restoration of wetlands with ecological sensibility.

Policy paralysis is yet another issue. The city still follows an outdated master plan from 2015. While some progressive steps, such as the establishment of the Bengaluru Climate Action Cell, have been taken, much remains to be done to make the laws dynamic and relevant to the city’s current needs.

Biodiversity must be included in our regional master plans, and laws must be amended to ensure that the last remaining green and blue spaces are managed with ecological sense rather than an infrastructure lens. This would go a long way toward ensuring good habitats for birds and other wildlife.

Rosy starling a migratory bird feeding on fruits inside the St Joseph

(The author is an ecologist and faculty member at ATREE)