Whistle while you work

I was up fairly early this morning and at my desk. I was rewarded by this. No idea what it is. Quite possibly a blackbird in our garden. We have a couple that seem to have adopted our garden as their own. I keep hearing them hunting in the leaves outside my window, which bothered me until I found out what it was! Sorry about the audio quality, it's on a small voice recorder, converted using mplayer. Delightful. Made my day