Thank you for your comments, Rupert and Tom!
Rupert: I had already done a bit of cropping and unsharp mask - I guess I tend to go a bit easy on both. There is the added fact that I love that particular tree, the only big tree in our garden, so I kept the trunk and branches as a "frame". Your crop looks good though.
Tom: Lovely chickadee. I can understand your sense of accomplishment getting that, but I have to say that for me it is swamped by the sense of frustration getting for instance this pic of a long-tailed tit with my manual 300mm:
(I have a perfectly focused second shot a split second later - of the empty branch!)
My 300mm f4 has lovely bokeh. I just don't want that all over my main motif!
I know practise improves manual focus speed (and I am old enough to have owned an Olympus OM20 with only manual lenses), but I would prefer to spend my energy getting better at positioning myself, and capturing the light and the behaviour better, and let the AF motor handle the focusing.