Theses and Dissertations

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    Organochlorine pesticides, population and reproductive success of fish-eating birds in select heronries in Tamil Nadu
    (SACON, 2013) Jayakumar, S.; Murlidharan, S.
    Colonial water birds are one of the major vital components of a wetland ecosystem. They serve as an excellent indicator of wetland health. In India. destruction of fresh water wetlands and entry of contaminants pose significant threats to the long-term stability of the population of colonial water birds and their habitats. Enormous quantities of man-made chemicals are used in modern agriculture. Despite obvious benefits, their indiscriminately has resulted in accumulation of residues in food and animal tissues causing environmental and ecological impact. Presence of pesticide residues, particularly persistent organochlorines in different biological and non-biological components has raised concern about their long-term accumulation and effects. Birds occupy different trophic levels in different food chains and hence are exposed to different concentrations of contaminants through their food. III effects of pesticides on wildlife. especially raptors, waterfowl and fish-eating birds have been extensively studied around the world. But, in India such information on birds particularly fish-eating birds (colonial birds) is limited. Although. some information is available on the residue levels of pesticides present in eggs of fish-eating and insectivorous birds in lndia, they fail to bring out the exact scenario of pesticide usage in agricultural areas and residue levels in eggs, and the consequent impact on breeding outcome. Further. there are 110 studies which have repol1ed the residue levels in eggs and simultaneously monitored the population of birds over a period of time in India. The present work was conducted in select heronries in Tamil Nadu with the following objectives; identify the heronries in Tamil Nadu, monitor the population and study breeding ecology of colonial nesting birds in select locations. document the residue levels of organochlorine pesticides in fishes, eggs and tissues of colonial nesting birds and asses the impacts.
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    Pollinator Visitation and Reproductive Success in Two Species of Mangrove Plants, in Bhitarkanika Wildlife Sanctuary, Orissa
    (Wildlife Institute of India, Dehradun, 1997) Pandit, Shalini; Choudhury, B.C.
    Visitation patterns to the flowers of Sonneratia caseolaris and Aegiceras corniculatum were investigated between December 1996 and April 1997, in the mangrove forests of Bhitarkanika Wildlife Sanctuary, Orissa. The objectives of the study were to determine the pollination effectiveness of the different categories of visitors by quantifying their rate of visitation. The effect of environmental variables on visitation was examined, and the importance of the visitors to the reproductive success of the plant was investigated by conducting exclusion experiments (Le. bagging flowers to prevent visitation). Nectar was analysed for volume and sucrose content in S. caseolaris, and the impact of predation on the reproductive success of the plant was examined. The results of the study indicated that the flowers of both plant species attracted a wide array of visitors and did not show a specialised relationship with anyone visitor species/category. Different categories of visitors were seen to vary in their pollination effectiveness for the two plant species. Environmental variables such as temperature, sun intensity and wind velocity were seen to influence the visitation of Lepidoptera to the greatest extent, and Hymenoptera to a lesser extent. Visitation by birds was found to be independent of the environmental variables. The territorial behaviour of purple-rumped sunbirds at the S. caseolaris site was seen to reduce visitation of other birds and of bees to the flowers of this species. Results of the bagging set-ups indicated that there was no difference in the pollinator effectiveness of the nocturnal and diurnal visitors. Reproductive success was not pollinator-limited in either of the two plant species.