And, migratory birds provide the straw in the wind. Birdwatchers say this year the number of migratory birds to Nangal Wetland has gone down, and the trend has been continuing for the past three years. Bar-headed geese, which came here for only three days, have shifted their winter abode to Gobind Sagar Lake.

An expert, who has conducted a study on the wetland flora, blames it on disturbance in the food cycle. He says he has observed shrinkage in the cell size of algae, especially spirogyra, and one reason for the phenomenon could be the industrial pollution. The major attraction for migratory birds in this wetland is the small fish, which feeds on algae.

The effluents from industries on the foothills of Himachal Pradesh, especially Golthai, and sewerage from nearby areas flow unabated in the wetland. Besides, the plastic waste hanging from the hillocks hemming the wetland also disturb the birds, which stay near the banks at night.

Disturbances caused by fishing boats, which were pulled back by the authorities only a month ago, also kept the birds away this season.

A birdwatcher says that global warming has also turned the heat on the habitat. The migratory birds, which used to reach by September 27, came in October-end last year. The ecologically-fragile wetland is also facing the problem of siltation caused by soil erosion wreaked by deforestation in Himachal hills.

Dr MS Johal, former professor at Panjab University's Zoology Department, says, "A thorough scientific study should be conducted to ascertain what ails the wetland. Due to the presence of vegetation in some of the areas, the visibility of the water reduces, thereby making it difficult for the birds to locate fish. About 30 to 40 per cent of the birds feed on minnows." The release of factory effluents has also lowered the visibility, says another expert.