I know the species very well and realise that they are not easy to capture in flight, well done:). Everything works for me but I agree perhaps the sky is a bit bright (?)
I have a program that you can download for a try out, although it doesn't render in the demo, that will help you with the sky since it has a grad neutral density filter. It has saved a couple of images for me:
Nik Color Effects version 3.0, I use the Select edition.