The pied kingfisher is one of the bird species living in India's capital
By Anu Anand
One of the world's most polluted and populated cities, Delhi, is home to 450 species of bird - more than any other capital city in the world except Nairobi. But it is unclear whether or not the birds will survive the continued growth of the megacity.
"Meet at 0600 at the banyan tree bund," said the bird watcher's e-mail.
"May you always hear the whisper of wings."
Birds like the green sandpiper survive the toxic sewage
"Is this a place a taxi driver would know?" I asked.
"Afraid not, but even a dumbo birder would know," came the retort.
I had been warned that bird watchers were eccentric, and here was evidence.
The following Sunday before dawn, I found myself in search of the elusive banyan tree bund - or raised embankment - and Delhi's secret bird life.
We skirted along one of the city's most polluted industrial areas towards the river.
I scanned the horizon, looking for trees in the distance, but all I could see was cheap office parks and a desolate ferris wheel etched against the grey sky.
We passed car body workshops, plastics manufacturers and road-side welding shops.
It resembled the set of a post-apocalyptic Hollywood movie.
How could this place host more than 400 species of avian life?
It is true that Delhi is home to several exotic urban birds.
Songbirds exposed to seriously polluted environments sing more, but they also die early
I always wake to the sounds of pigeons and crows.
Green parakeets chatter in our guava tree, their crimson beaks biting at unripe fruit.
At dusk, you can hear peacocks, those majestic winged divas, ululating in the most un-diva-like manner.
And one of Delhi's most distinctive sounds is the tremulous shriek of black kites riding the warm air currents.
These eagle-like birds of prey circle and swoop, sometimes flying close enough that you can hear the powerful pumping of their wings.
Still, I found it hard to believe that Delhi - one of the world's most polluted and populated cities - could top the list of bird habitats. Somehow birds still survive, feed and breed here.
As we neared the Yamuna river, we slowed down, looking for signs of a banyan tree or an embankment.
We stayed well away from the water... yet, somehow, birds still survive, feed and breed here
The river's stench, even filtered through the car's air conditioning system, was unbearable - the result of three billion litres of untreated sewage pouring into it everyday.
Its black, stagnant water convinced me we were on the wrong track.
But suddenly the taxi driver spotted an arch etched with the fading words, Bird Sanctuary.
Then up ahead, I saw a large banyan tree - its aerial roots hopelessly tangled as they reached for the ground.
We had reached our cryptic destination.
Nikhil Devasar, whose one-line e-mails had led me here, stood beneath the tree, sporting a camera with a megaphone-sized lens.
A so-called "twitcher", he is willing to jump on a plane at a moment's notice to catch a glimpse of a rare bird.
His India list currently stands at 860 species.
We had barely said hello when he pointed beyond a forest of reeds to podgy black cormorants nestled among the water hyacinths.
We also spotted purple swamp hens and rusty-black coucals, whose eerie lowing seemed to surround us.
In early summer, the Yamuna is packed with long-legged sandpipers, pond herons, and lesser whistling teals - ducks to you and me.
Until two years ago, hundreds of pink flamingos cut a breathtaking sight as they foraged in the shallow waters.
But global warming and the fast-melting of glaciers have pushed the water levels too high.
As Nikhil spoke, one eye attached to his lens, other bird paparazzi joined us.
Two teenage boys and several women - all sporting binoculars - and a portly, grizzled veteran, introduced as the "White Crested Thrush" - a reference to his billowing mane.
We stayed well away from the water, so toxic, it is fit only for industrial cooling.
Yet, somehow, birds still survive, feed and breed here.
Nikhil says the river, even in its poisoned state, guides species as they migrate down from the mighty Himalayan mountains, or up from the Deccan Plateau.
It is an avian compass, directing some species east, away from the harsh winters of Central Asia and others west towards Africa.
Signs of defeat
Whatever their destination, Delhi is a common stop.
Twitcher Nikhil Devasar is worried for the future of the birds
And yet, the "White Crested Thrush" (lawyer Anand Arya) told me the city is destroying its last few bird caravanserai with stunning efficiency.
He described his court battles to protect local habitats.
But signs of defeat surrounded us.
Mr Arya pointed to a new park where 9,000 trees had been cut down to make room for political statues.
An athlete's village and a Disney-style temple complex loomed ahead on the floodplain.
"Sadly, no studies have been done to tell us how the pollution is affecting birds long-term," he says.
"We do have a lot of species, but their numbers are down by 90%."
At 0700, as the tropical sun began to scorch, we retreated to a shaded underpass where the birders argued over what sub-species they had spotted.
And to lament the absence of others - bitterns, munias, Siberian cranes and vultures - all once plentiful here.
Mr Arya told me songbirds exposed to seriously polluted environments sing more, but they also die early.
As we walked under throbbing high-tension power lines running right through the sanctuary, he said:
"The light is often brightest just before it goes out."
How to listen to: From Our Own Correspondent
BBC Radio 4:
A 30-minute programme on Saturdays, 1130.
Second 30-minute programme on Thursdays, 1100 (some weeks only).
Download the podcast
BBC World Service:
Hear daily 10-minute editions Monday to Friday, repeated through the day, also available to listen online.
Read more or
explore the archive