PROBABLE REASONS FOR DECLINING POPULATIONS OF HOUSE SPARROW, PASSER DOMESTICUS (LINNAEUS) (PASSERIFORMES: PASSERIDAE) IN RURAL VELLORE DISTRICT, TAMIL NADU, INDIA.

M. Pandian 1 and S. Natarajan 2 . 1. Research Scholar, Department of Plant Biology and Biotechnology, Guru Nanak College, Velachery, Chennai600042, Tamil Nadu, India. 2. Professor, Department of Plant Biology and Biotechnology, Guru Nanak College, Velachery, Chennai600042, Tamil Nadu, India. ...................................................................................................................... Manuscript Info Abstract ......................... ........................................................................ Manuscript History

In recent decades, the species has undergone significant declines across the Eurasian portions of its distribution (Leasure 2011) and North-Western Europe (Prowse 2002; Mulsow 2005Mulsow , 2006. The Chinese campaign against P. domesticus under the perceived notion that these birds occur as invasive pests in China resulted in killing of millions of birds in 1958 (Deepa 2013). Since mid 1970's, rural and urban/suburban populations in the UK have declined by 47% and 60% respectively (Robinson et al. 2005). From 1979, rural populations of P. domesticus in Britain declined by 60%, but stabilized at reduced levels in the 1990s (Summers-Smith 2005). It is reported that the once widely distributed species in most parts of Europe and Asia is slowly disappearing from urban areas (Gulati 2005). Many hypotheses are postulated to explain decline of P. domesticus, such as lack of nesting sites in modern and renovated buildings (Vincent 2005  . Predation from the domesticated and wild cats (Felis catus, Carnivora: Felidae) and sparrow hawks (Accipiter nisus, Accipitriformes: Accipitridae), and the electromagnetic radiation from cell-phone towers are considered as reasons for their decline (Balmori & Hallberg, 2007). Passer domesticus populations are vanishing from different metropolises and in newly developing urban areas . A survey by the Indian Council of Agricultural Research confirms that the house sparrow population in Andhra Pradesh has dropped by 80% and in other States such as Kerala, Gujarat, and Rajasthan by 20%, while in coastal areas the drop is close to 80% ). According to a Bombay-Natural History Society's study, the population of P. domesticus is lower at present than in the past and this is consistent across the country (Citizen Sparrow 2018). International Union for Conservation of Nature (IUCN) Red List has evaluated the house sparrow's conservation status as 'Least Concern' (Birdlife International 2012).
In this paper, therefore, I sought answer to the question considering the growing concern over the decline of P. domesticus population in India in general: What are the probable reasons for decline of its populations in rural villages of Arakkonam and Nemili taluks, Vellore district, Tamil Nadu?  (Fig. 1). The principal occupation of people of these areas is agriculture followed by weaving. The altitude of the area is 81 m AMSL. Soil is made of red-sandy loam and black-cotton soil. The major crops of this area are Oryza sativa, Sorghum bicolor, Pennisetum glaucum, Eleusine coracana, Setaria italica, Saccharum officinarum (Poaceae), Vigna radiata and Arachis hypogaea (Fabaceae). Monoculture of Casuarina equisetifolia (Casuarinaceae) is common in the water-scarce parts of the taluks. Cultivation of ornamental flowers, and vegetables also occurs (vww.vellore.nic.in).The average annual rainfall of the district for the past 20 years With help from local people (12), 1715 houses covering 153 villages in these two taluks were identified in which active nests and populations of P. domesticus were found. The houses were surveyed between 0600 and 0900 hours and 1500 and 1800 hours over three months (February-April, 2017). Then adult residents of those 1715 houses were interviewed using a Tamil questionnaire designed to contain details such as type of house, numbers of active nests, numbers of birds observed in the vicinity of nests/houses, predatory animals, incidence of hunting/killing bird for meat, and impacts of domestic electrical appliances. The numbers of mobile phone towers in the villages were verified and listed. Other than these, other biological notes on P. domesticus populations and their nests were made by direct observation using a pair of Super Zenith field binoculars (Model No. 20x50 Field 3 O , Jack Berg, El Paso, Texas, USA). The total count was used to develop the numbers of nests, types of houses preferred, and numbers of birds. In addition, 153 senior citizens, former civic representatives, farmers, and womenfolk, were interviewed using data sheets in Tamil and the details of past P. domesticus populations and their population trends over the last 30 years were tracked and recorded. Photographs and videographs were made using a digital camera (HDR-CX130, Sony Corporation, Minato, Japan) without disturbing the nests and birds.

Results And Discussion:-
A total of 1903 active nests and 6452 individuals of P. domesticus were enumerated in the human habitations (1715) of 153 villages covering Arakkonam and Nemili taluks, Vellore district. Based on the results of interviews conducted using the questionnaire, the probable reasons for population decline of P. domesticus were deduced as discussed below. 624

Impact of powerlooms:-
Interactions with the elders of the villages revealed that prior to 1980, each street in the villages had hundreds of P. domesticus, which flew in flocks every day. They built nests in traditional concrete flat-terraced buildings, thatched/tile rooftop houses, cattle sheds, schools, Government buildings and street lamps. Sparrow also preferred to build nests in the vicinity of handlooms in the houses of weavers' community in 10 villages, such as Minnal, Narasingapuram, Guruvarajapettai, Valarpuram, Melkalathur, Paravathur, Sampathrayanpettai, Nagavedu, Nemili, and Panappakkam. Installations of handloom apparatus created many crevices/holes on the walls which became safe haven for sparrows to build nests. People in the weaver community and farmers believed that building of nests followed by successive breeding in their houses were good omens. Even the operations of handlooms created some noise, but the sparrows got accustomed to it and coexisted with the weavers. Likewise, sparrows became an integral part of the day to day activities of farmers in rural areas. This situation suddenly changed after 1980s. Power looms 625 had slowly replaced traditional handlooms in the rural areas and now 3022 power looms (Source: Assistant Director, Handloom & Textiles, Vellore district) are there in 10 villages where the weaver community is predominant. Hence the architecture of these houses changed resulting in the loss of nesting sites and noise pollution from power looms further drove away sparrows from the vicinity. The present investigation revealed that nests as well as sparrows were not to be found in the vicinity of buildings/houses where these 3022 power looms operate in the study area. The exact impact of power looms and its noise pollution on the nesting habits of P. domesticus needs further study. These dwellings which restrict entry as compared to the traditional houses have resulted in reduction of habitat suitable for nesting. Yet 50% of nests (n=3278) are in concrete houses. Sparrows avoid building nests on walls that are exposed to predators. They prefer to construct nests on lamps, electrical junction boxes, electrical fittings, ventilators, and holes and crevices formed on removal of scaffoldings from the walls after completion of construction in concrete flat-terrace houses having iron grill gates and windows with narrow bars, which preclude entry of predatory animals such as crows, cats, monkeys and sparrow hawks. The exact impact of modern buildings and renovated old buildings on the sparrow populations in the study sites is to be examined in detail.

Accidental Deaths:-
The Study revealed that electric ceiling fans which are common feature in every household pose a serious threat to sparrow populations as the birds are often killed by swirling fan blades. Such kind of mortality has been reported in 86 villages that were surveyed in this study. Five house holders have stated that during breeding season (April-May) in 2016, nests constructed on electric meter boxes were gutted owing to fire caused by short circuit. It is also revealed that in 15 houses, the eggs and broods fell down from nests accidentally causing destruction of eggs and death of broods.  626 Destruction of hedgerows:-Urbanization and contemporary landscaping are doing away with hedgerows and that has also contributed to disappearance of sparrows. Chamberlain et al. (2007) has observed that the destruction of hedgerows in private gardens and horticulture areas reduce density of P. domesticus populations. Development of urban areas results in losses of green space (Shaw et al. 2008) and existing vegetation harbor poor insect fauna caused reproductive failure of the birds due to lack of arthropod diet to its chicks (Southwood 2008). Destruction of vegetation on breeding ground has adversely affected sparrow populations (Heij 1985). Avian densities increased with arthropod richness (Thomas et al. 2011). Thick hedgerows around houses and native trees along the roads protected birds from predators, besides providing rich sources of arthropod fauna. Higher richness of arthropods through hedgerow management may increase the abundance and distribution of avian species which select for arthropod-rich habitat as a source of food (Aviron et al. 2007). Similarly house sparrows prefer to rest during day on hedgerows and loss of such hedgerows causes of loss of habitat and food.

Felling of native trees and invasion by exotic plants:-
Non-availability of water:-Sparrows prefer to take dust and water baths habitually. House sparrows create small saucer shaped dust pits and bathe communally before they roost. Dust bath might help clean the feathers and skin from external parasites (Ali & Ripley 1983). Traditionally rural folk used to store water in pots and other utensils in the backyards of houses, which attracted sparrows to take bath as well as to drink. Water supply in closed pipes, and covered water storage have prevented sparrows from enjoying such pleasures particularly during summer seasons. Bitumen topped or concrete road surfaces in rural areas have deprived sparrows of dust baths.

Non-availability of grains:-
Sparrows feed on grains such as paddy, pearl millet, finger millet, sorghum and other millets, which spill during harvest, transportation, drying, grinding, and storage in houses, shops, and mills. Only seven active nests were observed in shops. The study reveals as grocery articles are packed in polythene covers, there is no spillage of grains in shops. Further, lack of crevices in the buildings and use of steel shutters hinder movement of these birds. Online trade, modern packing of groceries and separate locked grocery storage in houses have prevented spilling of grains. This has caused acute shortage of availability of food grains to sparrows.
Garbage disposals:-Previously, rural people used to dump garbage in pits in the backyards of their houses. During decomposition, these organic materials encouraged populations of insects and worms, which were eaten by sparrows, or were fed to their chicks. Absence of such traditional solid waste management has resulted in non-availability of fauna to feed their chicks. Due to urbanization, spilled food grains and left-over cooked food are now disposed of in polythene bags and this reduces availability of food for the birds.

Impact of predators:-
In view of urbanization and increasing population in rural areas, generation of huge quantities of garbage and recycling processes at garbage dump yards has resulted in greater number of house crow (Corvus plendens: Passeriformes: Corvidae). Crows could be a nuisance for sparrows because of their kleptoparasitic behavior and their tendency to predate eggs and chicks from nests (Long 1981;Cramp 1994;Khera et al. 2009). In eastern Africa crows are known to pillage passerine nests (Lim et al. 2003). House crow, sparrow-hawks (Accipiter nisus: Accipitriformes: Accipitridae), cats (Felis catus: Carnivora: Felidae), monkeys (Macaca radiata: Primates: Cercopithecidae), and snakes are the potential predators to P. domesticus. In four instances noticed in the area of this study, monkeys had destroyed nests constructed on trees and shrubs in the backyards of houses. Common crows freely enter human residences through grill gates, windows, doors, and explore for sparrow nests, destroying eggs and chicks. Twenty-four house holders have stated that crows visit their houses chasing adult sparrows and predate eggs and broods. Increasing number of predators and their continuing attack on the thinning populations of P. domesticus, their nests and nestlings are principal causes for declining population of sparrows.
Mobile phone tower radiation:-Electromagnetic radiation from cell phone towers is also one other reason for the decline of sparrow population (Balmori & Hallberg 2007). However, experimental studies involving ex-situ simulations of different strengths of electro-magnetic radiations in Europe have yielded mixed results on their impacts on reproduction of birds, and no conclusive evidence has been produced so far. Interactions with villagers during this study revealed that even before the installations of mobile phone towers at rural areas, in the 1980s, P. domesticus started to disappear. The study 627 also revealed that 73.5% nests (n=1398) and 73.9% sparrows (n=4768) were observed in 116 villages where mobile phone towers are installed. Even after the installation of mobile phone towers, these birds survive in the villages where mobile phone towers exist. Hence, the exact impact of electro-magnetic radiations from the mobile phone towers on the survival of P. domesticus is to be studied in greater detail.
Superstition:-Some of the traditional health practitioners in the rural areas used to sell medicine called 'Chittukuruvi Legiyam' made with ingredients of meat of sparrow and the people believed that the consumption of either the meat of sparrow or legiyam (paste) has an aphrodisiac effect. Incident of selling of house sparrow meat at Karur district was reported in 2013, as a section of people in rural areas believed that herbal preparation of sparrow meat would enhance virility in men (Oppili 2013). The present survey revealed that incidents of hunting/killing of sparrow have been prevalent in 42 villages for meat due to such superstitious belief.

Conclusion:-
The probable causes for declining trend of P. domesticus was studied in 156 villages in rural Vellore district, Tamil Nadu. A total of 6452 birds, 1903 active nests, and mobile phone towers were counted in these villages (153). The replacement of traditional handlooms by power looms, structural modifications of houses to suit power looms, changes in the architecture of concrete houses, accidental deaths due to ceiling fans, declining areas of cultivation, replacement of native plants by exotic plants, destruction of hedgerows, non-availability water and mud to take bath, non-availability of food gains, predators and killing of birds for superstition may pose a threat to the populations of P. domesticus. Active nests and populations of P. domesticus occur in villages (n=116) where mobile phone towers are installed and the impact of radiations from such towers needs further study.