Your file size is only 51k when you could have used up to 200k. This indicates a lot of JPEG compression, which is taking a lot of detail out of your photo. Check the JPEG compression settings in your image editor and always try to save as close to the limit for a challenge as you can get it without going over.
This shot also looks a bit overprocessed on the birds body. I can't tell for sure what may have caused this.
I think I have one of these guys (or a close relative) that sits in the tree behind my house. He gets that same sort of look when I try to take his picture but leaves before I can get it! He looks a little washed out and mottled - like maybe the focus was a bit in front of him.