Bangalore lakes are infamous for mass fish kills. Sewage and other organic matter in water increases its biological oxygen demand leaving no dissolved oxygen in the lake for fish. Introduction of invasive and more resilient fish species has affected small native fish species too. Has this affected populations of birds that prey on small fish? Small blue kingfishers, pied kingfishers and terns are becoming extremely difficult to spot now (compared to 5 years back), at least in the lakes I frequent to, small fish absence could be a small factor to this trend.
In video:
1) Brahminy kite with a small catfish catch. Raptors have to tear their fish prey into pieces to eat them.
2) Painted stork preying on a huge catfish, they wait till their fish die before gulping them.
3) White throated kingfishers trashing its prey to make sure its dead?!
4) Small blue kingfisher with a small fish catch, this fish was caught at relatively cleaner waters.