By Dr S. Subramanya
Flat 497, C-7 Block,
Bangalore 560 064
Nearly 110 species of birds fully or partially dependent on water have been recorded utilizing the tanks in Bangalore.
This diversity of birds belongs to 6 avian orders and 25 bird families (List 1).
Of these nearly 50 % (54 species) are migratory visiting these tanks from beyond the Himalayas, mainly Eastern Europe and Central Asia between September to April each year (List 2).
Of these 110 species as many as 32 species have been recorded nesting within these wetlands (List 3).
The support for such diversity lies in the structure of the tanks with varying water depths and the presence of three different types of vegetation namely, floating (e.g. water hyacinth), anchored floating (e.g. water lily), emergent (e.g typha reeds, alligator weed) vegetation. Aquatic vegetation that occupy mainly shallow water zones of the lake influence the presence of as many as 37 species of birds (List 4).
These birds depend on aquatic vegetation for food cover and nesting requirements. Of this as many as 13 species of birds have been recorded nesting within the aquatic vegetation that grows within the water bodies of Bangalore (List 5).
Thus, maintenance of different aquatic vegetation is crucial for the presence and survival of most of these birds.
Excessive growth of some of the aquatic vegetation like water hyacinth and typha reeds that play an important role by providing foraging and nesting conditions for several birds need to be maintained by restricting their excessive spread by controlling their growth by regular monitoring and removal of this excessive growth.
Nearly 50 % of the birds inhabiting these lakes are migratory and some of them migrate from Central Asia and even from regions as far as Arctic Circle during winter months from late September-April. Their movement and occurrence in wetlands in and around Bangalore clearly indicate that their migratory movements and over-wintering habits appears to have evolved over the centuries based on the location and occurrence of these wetlands. Any damage to and disappearance of these wetlands may severely affect the migratory pattern of these waterbirds.