I have now used the Panasonic for wildlife at sea and on land. I am just as impressed with it then as I was at the beginning, especially the arrangement and control of the menu system which is vastly superior to the Sony effort. In many ways it is the ideal travel camcorder.
The only area in which I have found it to be less good than the AX53 is the autofocus under certain and unpredictable conditions. Even in good light on occasion, the camera has not focused on the bird or mammal in the centre of the frame but has picked on a patch of ground further away. In one case, the focus point it picked was a patch of grass in good light, in another, the pebbles of a beach. I just could not get the camera to autofocus on a cicada sitting on a tree trunk; again it eventually settled on the background. My impression was that, although I obviously did not have an AX53 with me to compare, the Panasonic's contrast-detection AF was not quite so good as the Sony's, although the latter does not get it right every time.
Another user I know has found the same problem with even a large antelope in the centre of the frame being ignored and focus being established on the background well to the left or right.
The answer, some my remind me, is to switch to manual focus but speed is often of the essence. Birds and mammals may be in view for only a matter of seconds and by the time several buttons have been pressed and a ring turned, the opportunity may have gone.
My Sony AX700 which has phase and contrast detection autofocus on its larger sensor does not suffer the problem of the contrast-only autofocus camcorders. It is perhaps unlikely that on-sensor phase detectors can be installed on the tiny sensors installed in the camcorders at the lower end of the market. However, there is a trade off between weight and sensor size so I may well keep my Panasonic for those occasions when I do not wish to or cannot carry anything heavier.
