2 things that jump out at me....
1) The random and sort of awkward positioning of the bird and its wings ( which sort of ties into composition ). I know these are just examples, but to me it looks like you just fired in hopes of catching something. I think with birds, you either want them sitting normally or with wings extended. Otherwise you need it to be clear what is going on. To me I can't tell if the bird just landed, if its about to fly off, if its cleaning itself ( well #2 obviously looks that way ), or whatever. They are just really uneventful which to me, makes them appear more amature or snapshot like. Birds can be a pain. Sometimes it take 100 shots just to keep one.
2) ( the biggest problem ) is the lighting. If you are not using flash, you need to always recognize your light source, how it is hitting your subject, and how to maximize that to your advantage. If this is a captive bird, move the cage, the light source, or use a reflector. If its a bird in the wild, move yourself so that the birds face and eye is being lit. Backlighting can work especially if using flash, or when used sparingly for a specific intended effect.
Focus seems pretty good to me, but its very hard to really be nit picky with that when its small sized low-res images.
Also, as others said, check out the rule of thirds. The birds body can still be centrally located in the frame, but ideally the head and eye ( or whatever you want to draw the eye to ) you would probably want closer to a rule of thirds ( not in all case, but in many )