AVAILABILITY, PREFERENCE, AND DISTRIBUTION OF THE NATURAL NESTING SITES OF HOUSE SPARROW (Passer domesticus) ALONG THE RURAL, SUBURBAN, AND URBAN GRADIENT IN MADURAI DISTRICT, TAMILNADU, INDIA

House sparrows are cavity-nesting urban birds. This study aims at identifying the natural nesting sites of house sparrows based on their structural preferences and distribution along the rural, suburban, and urban gradients in the Madurai district. A total of 169 study locations were surveyed between November 2020 and February 2021, using the line-transect method. Of these 169 sites, 132 were rural, 18 were suburban and 19 were urban gradients. The natural nesting behavior of the house sparrow was documented photographically. The data were analyzed using SPSS and Excel. Based on the obtained data, a total of 53 types of natural nesting sites were identified and classified as Cavity-type nesting sites in Building structures (CB), Cavity-type nesting sites in Non-Building structures (CNB), and Non-Cavity type nesting sites in Non-Building structures (NCNB). A total of 1820 natural nests were identified, wherein, 1338 natural nests were found in CB-type nesting sites which were of 19 different types, 253 were found in CNB-type nesting sites which were of 15 different types, and 229 nests in NCNB-type nesting sites which were of 19 different types. The most preferred nesting site in each of the groups was identified to be the space between wooden joists in buildings (CB), pipe holes in highway bridges (CNB), and electric meter boxes (NCNB). The CB-type nesting sites were found to be the most preferred nesting site along the rural, suburban, and urban gradients. The population of the house sparrow was found to have a strong positive correlation (R = 0.99) with the number of available natural nesting sites. Being an opportunistic secondary cavity-nesting bird, house sparrows exhibit nesting flexibility and adapt to non-cavity-type nesting sites when the cavity-type nesting sites were not available.