Nice shot; it reminds me of many of my early bird pics where I was wishing for a longer lens... I don't mean to be snobby, but my only advice for improvement is to save up (or even borrow if you're that way inclined, I can't criticise) and buy the the longest you can afford.
Edit: PS sorry if this was a deliberate "short" shot; my limited experience (plus some tuition) teaches me that it helps to ^go long^... the longer the better... try to fill up the frame without spooking the bird.