thanks BBW - my expectations were low as I was shooting with the sun behind the tree (subjects in evening shade) with a lot of wind, as can be seen with the tree, 500mm legacy lens etc I didn't even set the IS FL!
also surprised at the sound - better than I expected.
if they haven't fledged fully by Sunday I will go back and do it again properly with a tripod, DZ glass and 12 hours earlier!
To reduce that rolling shutter effect, the only surefire method is to up the shutter speed. Of course that is not always preferable in low light siutations, it's the best way to get less jerky results. It won't beat the effect, but it will help reduce its appearance.