The Jacana might soon be included in the ever-growing list of extinct wildlife, if present trends continue, warns VINOJ MATTHEW PHILIP.
WITH alarming regularity, one or more species of birds finds a place in the ever-increasing list of vanishing species. There are disturbing reports of two species of vulture the white-backed and the long-billed disappearing fast from their traditional haunts. The situation is alarming enough to provoke concerned persons into considering captive breeding of the white-backed vulture to restore the greatly reduced numbers at the "Tower of Silence" near Mumbai.
Field studies carried out by V. Gurusami and me over a few years in areas as far apart as the Northern districts of Tamil Nadu and the North Western Jharsuguda district of Orissa reveal a noticeable decline in the population of the bronze-winged Jacana, a wetland bird of the Jacanidae family. The only other Jacana to be found in India is the pheasant-tailed variety.
The Jacanas are totally adapted to wetland habitats with floating vegetation like lotus, lily, hydrilla and wetland rushes. They possess elongated toes and claws, which evenly distribute their weight on floating vegetation over which they scamper with great ease. Thus their other name "lily-trotters". Jacanas are polyandrous with female mating with more than one male during the breeding season and leaving the male saddled with the task of incubating the eggs and caring for the chicks.
Both kinds of Jacanas share common habitats, which are the jheels that support extensive, floating wetland vegetation. The pheasant-tailed species is a beautiful bird with deep chocolate brown and white plumage, a glistening golden-bluff oblong patch on the nape. Both sexes develop a sickle-shaped, pheasant-tail during the breeding season. The bronze-winged Jacana is attired in sober black with glossy bronze wings and a prominent white stripe behind the eye.
Our prolonged study at a 30-acre jheel on the northern fringe of Chennai supports the theory that the bronze-winged Jacana is vanishing from traditional habitats. The last bronze-wing was sighted in 1983. Frequent trips to other jheels in the northern districts of Tamil Nadu reveal the same depressing pattern. Recently, 200 pheasant-tailed Jacanas were seen at the Velacheri swamps in southern Chennai, but no bronze-wing. Strangely, pheasant-tails colonise the jheel in the northern fringe year after year. During each breeding season, synchronising with the Southwest monsoon (June-September), they breed and disperse during winter months. We have recorded nearly 400 pheasant-tails during seasons of favourable rainfall but not a single bronze-wing.
Natural predators like rats lurking at the jheel fringes would take a few Jacana eggs. Associate wetland birds like Diurnal Herons and Crepuscular Night Herons have been seen helping themselves to the eggs and hatchlings of the Jacana. Breeding Jacanas absorb the impact of natural predation by a built-in resilience. They seem to have no answer for sustained habitat loss due to human encroachment. Their only predictable response to encroachment is mass desertion. Polyandry and precocity of chicks (the chicks are ready to keep pace with the male parent bird hours after hatching) the bronze-winged Jacana's survival techniques are woefully inadequate and crumble in the face of relentless habitat loss.
If the present trend continues unchecked, it could very well be "Good-bye bronze-wings" in the next few years.
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