We observed one Short-toed Snake Eagle perched on topmost branch of tree.
Black Drongo
 It was surrounded by few Black Drongos. First we thought that Black Drongos mobbed the Short-toed Snake Eagle, as they were visibly pecking on its head. But after further observation we noticed some weirdness in situation. Black Drongos were behaving differently. They were not in their usual aggressive mode. Short-toed Snake Eagle seated quietly - unusually calm, if situation was being mobbed by couple of Drongos. Its looks like Black Drongos were picking something turn by turn from Short-toed Snake Eagle’s head. Then we assume Black Drongos may actually removing parasites from Short-toed Snake Eagle head. Whole situation suggested one more example of symbiosis. As Short-toed Snake Eagle is happy to get rid of some parasites and Black Drongos get food in return. 
Black Drongo


Black Drongo

Black Drongo

Black Drongo

Black Drongo

Black Drongo

Black Drongo

Black Drongo

So, its Spa-Time for Short-toed Snake Eagle...!