Rejects popular belief that biggest threat to the species is from mobile tower radiations Contrary to the popular notion that radiations from mobile towers are the biggest enemy of house sparrows, the species is rather being pushed towards extinction by large-scale use of pesticides. These results have been established by a study undertaken by Dr Rajiv Kalsi, Associate Professor, Department of Zoology, Mukand Lal National College, Yamunanagar. A three-year project (2010-2013) titled "Comparative Ecology of House Sparrow in Rural and Urban landscape in district Yamunanagar" was funded by the Department of Science and Technology, Government of India. The research, which concluded in the last week of November, was carried out at various locations of Yamunanagar district and parts of Ambala, Kurukshetra, Panipat and Karnal districts. "There is no significant effect of electromagnetic radiations on the distribution and dispersal of house sparrows," said Dr Rajiv Kalsi. The study reveals that the number of insects is decreasing due to high use of pesticides. This in turn reduces the availability of food for sparrows, especially their young ones. Besides, lesser availability of nesting cavities due to the changing pattern in the construction of houses - with more and more buildings having roofs with concrete lintels - is also one of the major reasons of the decline in the population of house sparrows. Dr Kalsi said, “The population of house sparrows is negligible in urban areas.” He said 335 natural nests and 100 artificial nest boxes had been monitored in the study area. The clutch size in house sparrows varied from four to five eggs and the incubation period from 14 to 18 days. The house sparrows had readily accepted the artificial nest boxes and sometimes nested for two to three times in them in one breeding season, he said. "House sparrows were usually encountered in rural areas of the district with a greater probability in areas with houses which had thatched roofs or roofs with wooden poles. Such roofs provide birds with ample cavities to make their nests. In the non-breeding season too, the sparrows preferred to remain in the rural areas, where they could easily get food in the form of seeds and insects," said Dr Kalsi. The study stated that 500 adult and nesting house sparrows had been marked with unique combinations of coloured rings to facilitate individual identification and monitoring. The intensive study areas, where birds were marked and released, were surveyed and those sighted again were identified. The findings The study reveals that the number of insects is decreasing due to high use of pesticides. This in turn reduces the availability of food for sparrows There is no significant effect of electromagnetic radiations on the distribution and dispersal of house sparrows The changing pattern in the construction of houses is another reason for the decrease in their number The population of these sparrows is negligible in urban areas as compared to that in rural areas