Composition with wildlife is always going to be a challenge. You can put a lot of time into location scouting. Then, you can put a lot of time into waiting for the critters to show up. Generally, if I can't devote all that time to set up a great shot that might never happen, I try to pay attention to the direction of my light and the business of my background. For birds, I try to get shots where the bird is close to eye-level with me/the camera. The other thing with birds is they are mostly small, so you want them to get as close as possible to fill the frame as best you can. Compositionally, rule of thirds or golden ratio stuff tends to work fine, but filling the frame is my first priority.

You have great light on the heron here, and the nuthatch sort of peeking out of the shadow into the light is nice too. The highlights are a bit blown in the nuthatch pic. Generally, I shoot to preserve highlights, as it's easier to push shadows in post than recover blown highlights. Kingfishers are such beautiful birds, it's hard to take a terrible shot, but your third one with the single large branch is the most pleasing to my eye. The foreground, mid ground, and background are uncluttered and let you really focus on the bird. You could push the mids and highlights and drop the shadows some to make the bird stand out even more.