If you are finding it difficult or very challenging to photograph birds in flight, thats understandable. It can be frustrating.
If you find yourself in this situation, then concentrate on bird portraits.
With bird portraits you can leave your camera in auto focus and simply wait until a bird lands on a perch. Again, make sure the eye is in focus and there is a catchlight in the eye.
I don’t use any image stabilization while the camera is on the tripod. The birds hop around so much by the time the stabilization kicks in the bird is gone. Personally I’m not a big fan of IS or OS while photographing back yard birds. I may use it while I’m photographing flying ducks but my shutter speed is usually hi anyway, honestly I rarely use it.
While shooting portraits I don’t use a shutter release.
Heres a few shots of perched birds. I place the prop near the feeder. The birds are looking at the feeder into the sunlight. Again utilize all of the elements I discussed earlier and I’m sure you will get some fabulous results.