Good exposure (although as mentioned above you can lower your ISO, get better quality files, without losing your shallow depth of field (if a choice) as your shutter speeds are really high (a monopod can be of service for slower shutter speeds). AS for composition I would try and go away for right in your face, right in the middle ready for a bird-seed packet illustration one. Try to move your bird(s) around the frame, make them play more with the environment (shapes and/or colors) to get a more complete "all-over" image which would also reveal the photographer from his/her choices (not just the subject unless it is all you are interested in, no harm in that either).