Silhouttes work with interesting shapes and dramatic lighting.

In this image, since sky is the background, your camera meter exposed for the sky. So you got the drongos dark. As such due to the dark colour, it is difficult to make out the eyes of the bird in normal lighting. Now you have completely lost the details in the drongos. I would have loved it if the sun would have been shining on your shoulders.

You should have photographed this as a vertical. The branches look nice. You can crop from both sides and try to lighten the drongos. The path to success is to experiment and analyse. I am sure soon, you will be very happy with your shots.