Yorkie, it looks like you've got a decent grasp of handling the camera.
I don't know how much you've cropped, but the more you can fill the frame the better. I would think that filling the frame with a coot should not be too hard with a 400mm lens. Maybe a little more patience to wait for a better opportunity. However, the main area for improvement is in the light and your angle of view onto the bird. I'd try to get lower down, nearer to eye level with the bird (or any animal). I also usually prefer creatures to be heading towards me rather than away. The eyes are very important. You need to be able to see them. For the coot it is practically invisible. It needs some light in it, and a catchlight ideally to add to the spark and sense of life.
For the greylag, given you've cropped, it seems an unusual crop to me. When a subject has a front end and a back end, be it a person, car, train, plane or animal it is common practice to leave more space ahead of the subject than behind. It is more interesting to see where the thing is heading rather than where it has been. It's a rule that can be broken, sometimes to good effect, but in this shot I think a more traditional composition would work better. The exposure looks OK but the light appears to be very flat once again - not the light I would seek for wildlife photography. Others may hold a different view.
Just as examples here are a coot and greylag in what I would regard as better light. No edits on these except slight crops. They might benefit from a little tweaking, but I just want to show the sparkle in the eyes....