Are the swamps of Dhaka good enough for Jacana?
We can still see the jacana in our city mainly because it was tough to fill up all the floodplains of the rivers in and around Dhaka. It was easier, however, to pollute and throttle the swamps. We wonder how much pollution will be too much for the jacana
We watch in awe and admiration whenever we come across the Bronze-winged Jacana walking on water in and around Dhaka city. We see the bird often lingering in the swamps of Purbachal, Savar and Keraniganj. What surprises us is not how effortlessly the bird walks on water; but how is it still subsisting on such poisoned water!
With abnormally elongated toes and extremely extended toenails the jacana is born to walk on the leaves floating on water. The eight toes of jacana's two gangly feet cover so much space on floating leaves that its ample weight, up to 350 gm, is supported quite well.
Jacana lives its entire life on the water. Most waterbirds such as waterhen, cormorants, herons, gulls, etc. cannot do that. They need something more stable than water under their feet to rest, roost and breed. Not the jacana; it does everything on the floating leaves. Noah's ark was the only place it ever lived on anything hard and stable.
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Once the jacana left the ark and settled in the waterlogged Gangetic delta, it never looked back. It feeds, frolics, sleeps, makes love and nests on water. We rarely see it step on dry ground. Instead of walking, it commutes between swamps by flying, even when those are very close by.
When a jacana flies up the toes and toenails dangle behind its body and looks as if the bird is carrying eight sharp and shiny steel-knives. Male or female, the jacanas do not come out of a swamp without the cleanest nails and the best of pedicure.
Even though male and female jacanas look alike, we can tell them apart because the female is bigger. Female is also the dominant sex in the polyandrous jacana community. We have seen the females of the small marshes in Dhaka keeping harems of two to three males.
The female maintains a territory for her harem and keeps other females at bay by screaming and posturing. Within the harem, every male maintains his territory and keeps other males out of it by showing-off and shrieking a high-pitched protestation 'seek-seek-seek'. From the squealing of jacanas we often get to know how active a marshland is.
Male jacana takes care of all household chores including incubation and chick rearing. The female lays four large eggs on a pad of floating leaves. The male starts incubation from the first egg. He holds the egg between his forewing and body. That is the only way to keep the egg warm while sitting on wet leaves.
With his wings, a male can usually hold up to four eggs close to his body. When necessary he walks short distances with the eggs tucked under his wings. We have seen the males brooding young chicks under their wings in the same way. We saw a male with four chicks under his wings run away from us quite fast.
Just after hatching, the jacana chicks walk on water with papa and pick up their own food - tiny insects and small invertebrates hiding in the floating vegetation. At night, the chicks must huddle under papa's wing for warmth and protection from predators.
With predators both in water and air, the life of a flightless chick in the care of a single parent is not an enviable one. Very few chicks survive to attain adulthood. We call a female or her harem a high achiever if she, with twelve eggs bequeathed to the three males, produces two adult jacanas in one breeding season.
The number of successful harems must have been dwindling in the swamps of Dhaka for quite a while; but it may still be better than many of our other cities and towns. We saw how the Bronze-winged Jacana population collapsed in the past two decades in the neighbouring Munshiganj town, once a stronghold of jacana.
We can still see the jacana in our city mainly because it was tough to fill up all the formidable floodplains of the rivers Buriganga, Dhaleshwari, Sitalakhya, Turag and Balu in and around Dhaka. It was easier, however, to pollute and throttle the swamps; and we accomplished that pretty well. We wonder how much pollution will be too much for the jacana.
We continue to be delighted by the sights and sounds of the foraging jacanas as we walk past the swamps in monsoon. Rain does not interrupt the daily chores of the jacana; their sleek feathers do not get wet in rain. Jacanas love to be out in the rain and are happy to have the swamp all to them when other birds have left to take shelter from a downpour.
Every monsoon gives the jacanas a new lease of life. Rainwater dilutes the poisons we keep pouring into the water. In monsoon the swamps look green and exuberant, and smell less awful. Profusion of the floating vegetation produces an abundance of insects. Jacanas feast on these insects and get ready for the tumultuous time of courtship in the fall.
