Unknown to Felix, Nightwing's sharp eyes had indeed spotted him when he walked between the trees. This was more confirmation than give-away, as there aren't many other places to hide out here. Still, all he knows is that Felix is amongst the trees, but not where. He drifts down in wide circles, hoping to spot some other clue as to his location, and eventually lands on the ground with a heavy thud. Felix will definitely hear that.