This is not one of my best shots ! :( yet an interesting bird ...
Drongos (there are several species in India) are seldom easy to photograph largely because of the black and the dark purpley - blue even green colours that are sometimes iridescent. They tend to exist in the shade too.
The details here are ...
5D Mark 11 with a 70 to 200 mm f4 zoom @ 192mm handheld
ISO 400 with no added exposure
1/50'th @ f5.6
It's a nice clean shot of this elusive species. A bit soft due to hand holding at 1/50th. It could be warmed up a bit and cropped from the left to get the bird away from center.