Hi, Jeni, what a pretty bird and I like that you caught him/her singing and with a catchlight in the eye. It looks pretty soft to me and has halos around it, perhaps from sharpening? Is this a large crop? You could probably eliminate the leaves and partial branch at the bottom; they are not adding anything to the composition.
Great bird and nice singing pose Jeni! Eye contact is good, and the exposure is pretty good. The image is soft, and looks like it might be a big crop. For hand held shots at 420mm, try for a faster shutter speed if possible. You used ISO 320, but ISO 640 would have looked almost as good in terms of noise and would have given you 1/800 shutter speed. Thanks for posting!