Hi Malcolm
I've often seen GC Grebe fly. However, this is only when they have been disturbed/in immediate threat. In every occasion the threat was a speedboat or some other powered vessel on the lake or sea. I've noticed they fly very low over the water, a bit like Shag, with quite fast wing beats in a level flight. HOWEVER generally, all grebes, including GC, I noticed, tend to dive themselves out of danger rather than fly - they can dive far quicker than they can take off. Little Grebe, for example, need to run over the water for some distance before becoming airborne and I think Ive only since this once! Some Grebe are also completely flightless during the Autumn moult, when they loose their flight feathers along with everything else, Slavonian Grebe and I think Redneck and Blackneck do this too, but not sure, - a bit like ducks in eclipse - and they are totally useless on land. They more than make up for this by being excellent divers and swimmers which are the strength of the species rather than aerial survival skills.