What a nice capture, that berry in its beak completely makes the shot.
The image looks like it is straight out of the camera and has no editing; I think it would be great to get this into some editing software and play around with the composition through cropping the original photo. At the moment there is a lot of space around the bird, it would be great to have a closer crop, keeping the main branch as a leading line, but losing a lot of the distracting branches in the top left corner of the image.
As you say yourself, this was a spur of the moment shot, and as a snap shot it is very good. It is a shame the blurred branches closer to the camera detract from the bird slightly, but the branches in the background that go slightly out of focus are very nice. Unfortunately in situations like this there isn't much you can do about what is between you and the subject of your photograph!
All in all a nice capture, that could be improved with a little bit of a crop!