There has been a significant rise in the number of resident birds turning to the polluted waters of the Mula and Mutha Rivers in search of food and habitat since fresh water bodies around the city are drying due to scanty rainfall. These birds are increasingly feeding on a fish species called tilapia, which accumulates heavy metals and other pollutants in its tissues, and may, therefore, be toxic.
Satish Pande, ornithologist and founder-president of Ela Foundation, an NGO devoted to nature education and conservation and Anand Padhye, associate professor of Zoology, Garware college said there has been an increase in the number of birds such as the painted storks (threatened species), grey herons, Glossy Ibis, White Ibis and a few Egret species on the Mula-Mutha rivers. Usually these birds avoid the Mula-Mutha on account of human disturbances here, restricting themselves to fresh water bodies which are relatively pollution-free. Mula and Pavana are polluted with industrial effluents, while Mutha has sewage waste. But, the delay in rainfall and the consequent drying up of water bodies has pushed these birds towards the Mula-Mutha. The situation is worrisome as the birds are feeding on Tilapia, which has a lot of polluted matter in its body. If the amount of pollutants in the fish is huge, then it can cause the birds to die or even affect their breeding processes causing the egg shells to break prematurely. Consumption of Tilapia can thus prove to be harmful to these birds. Neelesh Dahanukar, an Indian Institute of Science Education and Research (IISER) fellow, said that Tilapia can survive in polluted waters, while studies have shown that heavy metals such as lead, zinc, copper among others, present in a polluted water body enter the fish’s tissues. Higher organisms eating the fish will therefore have these metals accumulated in their body. “Scanty rainfall leads to an increase in the concentration of the organic matter in the river, eating up all the oxygen. Furthermore, if the Tilapia in these water bodies has high amounts of toxic matter, then the birds consuming such fish can even die” said Hemant Ghate, head of the Zoology department at Modern College.
