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Text and Images By Soumya Kundu

Genesis

In the district of Murshidabad (state: West Bengal), the main channel of the Ganges river, or Ganga as we call her crosses over to Bangladesh. A distributary of the Ganges called Bhagirathi starts near Giria (northeast of Jangipur in Murshidabad) flows south through West Bengal for 190 km to join the Jalangi river at Nabadwip in the district of Nadia. Thereafter, the river is called Hooghly. Bhagirathi, once the main channel of the Ganges, lost her glory when the Ganges shifted her main course westwards towards Bangladesh. Today, Bhagirathi in addition to the water she receives through the natural river channel is boosted by the water diverted from Farakka Dam through the 38.3 km long Farakka Feeder Channel.

Bhagirathi is a river full of character. She runs a meandering course through Bengal. Her capricious nature has created ox-bow lakes, mid-channel bars, interesting meander geometries, and lateral migration along her course. Around 1989-1991, the youthful river shifted eastward while giving birth to an oxbow lake on the western bank between Sajiara (district Purba Burdwan) and Mayapur (district Nadia). Thus, at the border of the districts, Nadia and Purba Burdwan was born a 9 km long freshwater oxbow lake with a water area of around 3.5 sq km (shrunk to 2.19 sq km in 2017). The local people named her “Chhariganga”. The villages on the northern part of the lake are known locally by the names Chupi and Kasthashali. The entire area including the lake (except for a few villages like Idrakpur) lies in the Purbasthali-II block within the Kalna subdivision of Purba Burdwan. Hence the lake is also known as Chupi Beel or Purbasthali Oxbow Lake. 

However, Bhagirathi did not abandon her child altogether. She continued to provide nourishment to her newborn through an umbilical cord-like channel that still connects the lake to her mother at the southern portion. To this day, Purbasthali Oxbow Lake continues to receive fresh water, silt, and nutrition through this channel all year round and in large quantities during the monsoon.

Nature blessed this child of Bhagirathi and soon the aquatic ecosystem of this oxbow lake of Chhariganga became rich in biodiversity. Aquatic plants of all types viz. floating, emerging and submerged started to grow naturally. Fishes abounded, as were other insects and crustaceans. As it happens across the globe, an abundance of one lifeform helps to sustain other lifeforms in that ecosystem. The same happened at Purbasthali Oxbow Lake. The migratory birds were quick to find this flourishing ecosystem and they started descending on the lake in large numbers for food and rest. The local resident birds also moved in and made the lake their feeding, hunting, and breeding grounds. It is believed that as many as fourteen thousand waterbirds used to congregate in the lake around the year 1992. In 2013, a census of twenty common waterbirds (resident, migratory and local migratory) in the lake put the count at close to ten thousand individuals.

Shoot Them, Eat Them

Purbasthali Oxbow Lake is surrounded by villages and is close to the major town of Nabadwip and the temple town of Mayapur. As early as 1988, when the lake was in the formative stage and not fully cut-off from Bhagirathi, the people around had started to notice the huge congregation of waterbirds in winters. Poaching of migratory birds became rampant. Awareness about conservation was minimal and the police were more occupied with the deteriorating law and order situation of that region. Enforcement of the Wildlife Protection Act took a backseat. The poached birds were often consumed by the locals for the delicious meat (as described by a local boatman) and also sold to wayside eateries to be cooked for prospective clients. In the year 1992, a local NGO named Junglees spearheaded by Raja Chatterjee started a mass awareness campaign with some help from the government. Pamphlets urging the villagers not to kill birds and to treat them as friends were distributed. Workshops were held with various stakeholders. The major stakeholders were the boatmen who earned a living catching fish in Purbasthali Lake. Purbasthali Lake hit the headlines of several regional and national level newspapers (see The Hindu, 6th March 1995 report by Parth Sanyal titled “Will these birds return?”). Sustained campaigning, liaison with the law enforcement departments, and the success of ecotourism helped to eventually stop poaching activities. Today, poaching is no longer a major threat to the migratory birds arriving at the lake.

A Bird Photographer’s Paradise

On a cold foggy morning in January, I was greeted at the Chupir Char by the familiar smile of my favorite boatman. I settled down in his small country boat with my mobile, binoculars, bird-book, camera, a heavy telephoto lens, water, and some food. Birdwatching from the boat in Purbasthali is a marathon eight-hour-long session. Small quantities of food and water are a must. As the majhi rowed the boat and steered it away from the banks, I marveled at the crystal clear waters of the lake. The fog had just started to lift and there was a promise of a clear blue sky. Sailing on the lake is itself a blissful affair. The fact that there are no motorized boats on the lake coupled with the fact that the birds do not treat the country boats as a threat, allows photographers to approach very close to the birds. The low height of the country boat lets you shoot most of the open water birds, wader-birds, and kingfishers at eye level.

We spotted a Common Kingfisher Alcedo atthis perched on a short bamboo pole jutting out of the lake. He had just caught his morning fish and we witnessed the tossing, turning, and flipping before the meal was gulped down. To be within a distance of six feet of a Common Kingfisher and to witness and capture such moments brings great joy. The serenity was only to be broken by the whistling calls of an approaching flock of birds. The large flock of Lesser Whistling-Ducks Dendrocygna javanica flew right over our heads. We saw several large flocks of Lesser Whistling-Ducks throughout the day. Lesser Whistling-Ducks are local migrants. They congregate in large numbers in winters at the lake. Once the winter is over, they disperse in smaller groups to other smaller water bodies nearby, where they breed. I scanned the birds sitting inside the Water Hyacinths Eichhornia sp. carefully with my binoculars hoping to find a Fulvous Whistling-Duck Dendrocygna bicolor but luck was not in my favor that day. Instead, I found a Baillon’s Crake Zapornia pusilla, a beautiful small migratory crake scampering over the floating plants. 

Then came the ubiquitous Little Grebes Tachybaptus ruficollis. You spot them and the moment you point the lens, they vanish inside the water, only to resurface several feet away. A small group of seven Cotton Pygmy-Goose Nettapus coromandelianus was spotted by my majhi. It requires mention that there are a few experienced majhis at Purbasthali who are not only exceptional spotters, but they have picked up the English names of most of the birds from the birders who come to the lake.

The Bronze-winged Jacanas Metopidius indicus, Pheasant-tailed Jacanas Hydrophasianus chirurgus, Grey-headed Swamphens Porphyrio poliocephalus were found in plenty flitting in and out of the Water Hyacinths thickets. The Great Egrets Ardea alba, Purple Herons Ardea purpurea, Grey Herons Ardea cinerea were also observed waiting patiently for their catch. These species are the permanent residents of the lake and they breed in and around the lake. The Black-winged Kite Elanus caeruleus appeared briefly, hovering over the lake. It had no business at the lake. Its interest lay in the agricultural fields on the banks.

Along the banks, there were large tracts of soft mud where the water was only an inch or two deep. Here at the edges, I photographed a beautifully camouflaged Common Snipe Gallinago gallinago and saw several other migratory waders like the Common Greenshank Tringa nebularia, Spotted Redshank Tringa erythropus, Common Sandpiper Actitis hypoleucos, Wood Sandpiper Tringa glareola, Green Sandpiper Tringa ochropus, Kentish Plover Charadrius alexandrinus, White Wagtail Motacilla alba, Western Yellow Wagtail Motacilla flava, Citrine Wagtail Motacilla citreola and one single individual of Little Ringed Plover Charadrius dubius. It was evident that there was plenty of food for them in the mud to survive. In the distance, a flock of Cattle Egrets Bubulcus ibis followed two bullocks as they dug the farmland. At the shallow edge, the Asian Openbills Anastomus oscitans were probing for snails. A pair of Grey-headed Lapwings Vanellus cinereus stood motionless on the slightly raised mud embankments.

However, for the bird photographers, the prize-catch is the beautiful Red-crested Pochard Netta rufina and the powerful fish-loving Osprey Pandion haliaetus. Eurasian Marsh-Harrier Circus aeruginosus also brings a smile to their faces. All these three species are winter migrants to the lake. I myself had no specific targets for the day but when I saw my majhi struggling hard to create a path through the waterway clogged by massive growths of Water Hyacinths, I sensed that he was up to something. After half an hour of struggle through the Hyacinth thickets, the boat reached clear waters. Lo and behold. In front of us were around twenty-five Red-crested Pochards. The light being favorable, I took some beautiful shots. Needless to say, I was partial to the males. By taking advantage of the low seating position and by positioning the boat for favorable light, photographers often make beautiful takeoff shots of the pochards and other ducks from this lake. The reason why Red-crested Pochards stick to certain parts of the lake would be revealed later.

The Red-crested Pochards brought good luck. We soon spotted four to five individuals of Ferruginous Ducks Aythya nyroca nearby. As for Tufted Ducks Aythya fuligula, we found only two of them. Through the binoculars, quite far in the distance on a patch where boats could not reach due to shallow waters, we spotted hundreds of Gadwalls Mareca strepera, a few Northern Pintails Anas acuta, several Glossy Ibis Plegadis falcinellus, and a few Black-headed Ibis Threskiornis melanocephalus. 

Emergent vegetation like the Cat-tail/Hogla Typa sp. and other tall grasses had claimed certain parts of the lake. In these patches, we found the Clamorous Reed Warbler Acrocephalus stentoreus and the Brown Shrikes Lanius cristatus. Both the species are long-distance migrants who spend the winter at the lake. A resident Greater Coucal Centropus sinensis and a couple of Long-tailed Shrikes Lanius schach were also spotted. It would be unfair if I make no mention of the cormorants which were spotted in abundance. The lake is a perfect place to study the shape of the beak and the color of the eye of the migratory Great Cormorant Phalacrocorax carbo and Indian Cormorant Phalacrocorax fuscicollis. Since all the three cormorants can be found in one place, their sizes can also be compared.

Around mid-day, we observed the hovering of a Eurasian Kestrel Falco tinnunculus. The lull of the afternoon which had set in was suddenly broken by a cacophony of bird calls as a large flock of resting water birds took to their wings in a hurried manner. Investigating the cause, we found a Eurasian Marsh-Harrier descending from the sky. 

The abundance of kingfishers at the lake was proof that there were plentiful fishes. At the end of the day, four species of kingfishers were photographed, viz. Common Kingfisher, Pied Kingfisher Ceryle rudis, Stork-billed Kingfisher Pelargopsis capensis, and White-throated Kingfisher Halcyon smyrnensis. The White-throated Kingfisher which is the black sheep of the kingfisher family was spotted with a massive catch of a frog.

I forgot to mention our constant companion, the Barn Swallows Hirundo rustica. With relentless energy and in large numbers they kept flying around the boat, swooping down close to the water to hawk insects in flight. At times, they would rest at the tip of the jutting bamboo poles. In spite of their diminutive size, the blue metallic sheen of their feathers and the row of white spots on the tail (visible only in flight) made them look very attractive.

The sun was about to set and I was about to wrap up for the day. But the show was not over. The sky was filled with innumerous small birds which flew haphazardly all across. These were the Small Pratincoles Glareola lactea. They were the evening visitors to the lake who came for the flying insects.

With tons of images on the cards and with the ebird checklist showing more than fifty species recorded, I was a happy man ready to head back to my home in Kolkata. Kolkata is four hours drive away. By train, the nearest station is Purbasthali from where electric rickshaws are available for a drop to the Kasthashali Chupir Char picnic spot. The boating starts from this spot. Trains for Purbasthali leave at regular intervals from Sealdah and Howrah stations in Kolkata.

The Red-crested Pochards of Purbasthali

After a long migration from their breeding grounds in Central Asia, the Red-crested Pochards arrive at Purbasthali Lake around October and November. The long migration takes a toll on their fat reserves and leaves them totally exhausted. They look haggard, dull, and almost ugly. They feed voraciously at the lake and regain their beauty within a month of their arrival. It had intrigued me for a long time why Red-crested Pochards were more choosy than other migratory birds and stuck to only a few wetlands in Bengal.

I found the answer on one outing to Purbasthali. Luckily that day, I had with me a bright young lady who was a Zoology student. Taking photographs was not the main priority for that day. We spent more time observing birds, having fun, and even pulling out different aquatic plants with the help of oars. Whoever has been to the lake, cannot help but marvel at the beauty of the submerged plants beneath the lucid waters. After pulling out one such aquatic plant, I was photographing it with my mobile, when she casually remarked, “Sir, this is Chara. Don’t mistake it for an aquatic plant though it looks like one. These are algae.” There was no hesitation on her part. She was sure of the identification. I made a note and returned home.

As I was reading up on the Chara genus I learned that Chara sp. constitutes a significant part of the diet for the Red-Crested Pochard. Flashes of conversation with the majhi came back to my mind. The majhi had told me that these pochards would stick to only those parts of the lake where a certain underwater aquatic plant grew in abundance. It all made sense. This macrophyte, this algae of genus Chara was probably the reason why the Red-crested Pochards make Purbasthali Lake their wintering grounds.

The Macrophytes of Purbasthali Lake

The biota of the lake comprises several species of macrophytes or aquatic plants. The health of these macrophytes and their diversity are indicators of the health of the ecosystem and play a vital role in sustaining several lifeforms including birds. Some macrophytes recorded from the lake are broadly categorized and outlined below:

Emergent

• Macrophytes are rooted in the lake bed but a major part of the plant is out of water.

Species: Typha sp., Arundo sp, Phragmites sp, Alternanthera sp, Panicum sp, Polygonum sp, Hydrochloa sp, Scirpus sp, Juncus sp, Eleocharis sp, Carex sp, Hydrocotyle sp, Cyperus sp, Monochoria sp, Hygrophila sp, Colocasia sp, Centella sp, Commelina sp, Ipomoea sp, Sagittaria sp, Cynodon sp, Enhydra sp, Marsilea sp

Free Floating

• Macrophytes which float freely on the water.

Species: Salvinia sp, Lemna sp, Wolffia sp, Pistia sp, Eichhornia sp

Rooted With Floating Leaves

• Macrophytes which are rooted in the lake bed with floating leaves.

Species: Trapa sp, Ludwigia sp, Nymphoides sp, Nymphaea sp, Brasenia sp.

Submerged

• Macrophytes which are entirely within the water.

Species: Ceratophyllum, Vallisneria sp, Elodea sp, Cabomba sp, Hydrilla sp, Myriophyllum sp, Chara sp, Potamogeton sp, Ruppia sp, Najas sp, Ottelia sp, Aponogeton sp

Over the years, Eichhornia sp or Water Hyacinth (Kachuripana in Bengali), a globally invasive weed has posed a major problem for the lake. Their prolific growth fills up entire sections of the lake affecting the growth of other aquatic plants and making the waterbody impossible to navigate by boat. The proliferation of Water Hyacinths may also be a warning indication that the lake may be slowly transitioning from an oligotrophic water body to a eutrophic water body. Eutrophication is caused by the presence of excess nutrients in the water. Eutrophication is undesirable as it causes massive plant and algal growth, depletes the dissolved oxygen content, and affects fishes and other aquatic life forms. The excess nutrients come from the monsoon silt, human sewage waste, and leaching of fertilizers applied to the adjacent agricultural fields. It is to be remembered that the lake has a large catchment area that feeds the lake with rainwater.

Emergent species like the Hogla grass Typha sp, Nalkhagra Phragmites sp, and other tall grasses are also slowly increasing their territory, thereby diminishing the total water area of the lake. The water in the lake is alkaline and it still continues to be fit for irrigation. Turbidity is also low. 

Life Around The Lake

Village life around the lake is partially dependent on the lake. The main activity on the lake is fishing. There are several fishermen who catch good quantities of fish daily from the lake. At least twenty to thirty species of fish, most of them common in the Bhagirathi river, are caught in the lake using nets. To maintain navigable water routes in the lake, the fishermen community engages in clearing Water Hyacinths once every year. Farming is practiced using water from the lake for irrigation. Bathing at the ghats is also a common activity. 

In the winter months, tourism activities like picnics, boating for leisure, and hiring of boats for birdwatching, ferrying of tourists in rickshaws augment the income of the local people substantially.

Threats To The Ecosystem

Several anthropogenic factors pose a serious threat to the ecosystem of the lake. There are farmlands on the banks of the lake. Taking advantage of the low water level in winter, farming is done right on the bed of the lake in certain patches. Fertilizers and pesticides applied to the crops leach out into the lake. The presence of two large brick kilns in the vicinity is not helping either.

Picnic spots right on the bank of the lake create pollution in the form of thermocol plates and plastic waste. Noise pollution from loudspeakers in the winter months is another common problem.

Jute retting practiced during the monsoon months in certain sections of the lake is a major threat to the water quality of the lake.

A few years back, an ill-planned road connecting the island village of Idrakpur to the mainland was constructed right over the lake. The free flow of the water around the oxbow lake was thus cut off.

Another natural threat is the siltation caused in the narrow channel at the southern end which brings fresh water and fish from Bhagirathi into the lake. The character of the lake is bound to change in case the channel gets choked up in the future.

Conclusion

  Bhagirathi continues to nurture her child but it remains to be seen if we humans will take good care of her health. The migratory birds will continue to return to this wintering ground as long as “Chhariganga” remains in good health.

** End **