Graham, the 'problem' with this image, if there is one... Is the Levels setting. I took the liberty of taking the JPEG into Ps and checking the levels, the original image appears a bit 'flat', lacking in tonal range. This was confirmed in Ps - Levels.
I moved the white point to the end of the image data on the histogram and added a little contrast. No doubt further tweaking could improve the image but *technically* the image is now much better. I feel the lower edges of the bird are too clean cut... it kind of confirms this is an image merge, I would have expected some texture along the lower edge.
This is the result of the Levels setting: