Shooting birds in flight is by far the most difficult type of bird photography in general. For me photos of flying birds will be the most expressive and impressive.
Birds in flight should not be filmed on cloudy days. The best time for photography is when the sun is low on the horizon. This light works especially well when the photographer manages to catch a bird with its wings raised up, because in such a frame the sun illuminates the inner surface of the wing well, which always looks spectacular.
I practice on big goals. Large bird shots were a starting point for me when I started with photography and were be a great opportunity to develop my own skills.
Photos with Nikon d5700
Edited with Snapseed
Thanks for your attention.