Up your shutter speed for one thing. You're shooting at 500mm your shutter speed should be at least 1.5 times that focal length. Birds fly fast and if your shutter speed isn't fast enough, you'll get blurry photos. Birds in flight, mine are usually shot at 1/1000s but some have need higher than that. My Pigeon was shot at 1/1600s. Birds move even sitting still, they flutter so you need a higher shutter speed to stop them and not get blurry photos.
Other photographers will tell you to use a tripod. I have never been able to capture a moving bird using a tripod. Panning is too slow. Maybe you can. The lens you have, is it fairly heavy, then you need a tripod to hold it and the camera steady. SR is nice at times, but you should never have it turned on if you're using a tripod. Documented that SR on a tripod can cause blur photographs.
Fstops. Higher ones in bright blue skies will render the sky the color it's supposed to be, em, blue. Higher fstops will also get you more details in your subject. I think now would be a good time to tell you to buy
Bryan Peterson's book...Understanding Exposure.