Asan wetland is a rich, diverse and a well notified conservation reserve for sustaining a large migratory avian diversity. Migratory birds are an important biotic component of the wetland ecosystem as they occupy several trophic levels in the food web of wetland. Habitat ecological study of migratory and local birds in Asan wetland has been done during the winter season. The Asan wetland provides an optimum suitability of natural habitats for breeding, roosting, feeding etc. to rich repository migratory avifaunal population and supports them for their annual migratory behaviour. The 21 migratory species in different flocks from four zones of wetland were observed during the study period. The maximum number of flocks were recorded in morning in Zone I but the high abundance was observed in Zone IV. Mostly the birds are carnivorous and feed mainly on Insects, Zooplanktons, Crustaceans, Water bugs, flies etc. The wetland is quite rich in nutrients and contributed significantly to enhancement of ecosystem productivity as a distinct food web cycle provides a substantial food spectrum to the avian fauna. The ecological characteristics of wetland were studied as dissolved oxygen in the range of (5.6-7.2 mg/l), Sulphate (1.32- 1.36 mg/l), Calcium (24.17-25.43mg/l), Magnesium (12.83-13.27mg/l). The nitrate (0.29 mg/l -0.33 mg/l) and the phosphate (0.659-0.76 mg/l ) were recorded in all zones. The nitrate and phosphate are the limiting factor to denote the present trophic status of wetland in relation to productivity and status of species richness of biotic communities. The present study revealed that the availability of nutrients in wetland play a significant role in the selection of particular ecological niche by the migratory avifauna.
