Strange sight

Today, I was in a car, near Cochin/Kochi, passing over a bridge, when I saw the strangest sight; in the air I could see a big bird--looked like a hawk, but may have been only a crow, and a much smaller bird flying very close to each other.  At first I thought the bigger bird was intent on catching the smaller bird.  But then, as I watched, it looked almost as though the smaller bird was trying to take a ride on the bigger bird's back or else just plain harassing that bigger bird, or chasing it.  Now there is a small black bird, with a swallow like tail, which attacks crow.  But I couldn't see any evidence of a tail like that.  Wish I could have watched longer to know what was going on..........