We call the "ballerina stretch" duck taichi :) My daughters even gave competition scores to our ducks: the winning movement has to be smooth and long, with an elegant lazy finish.
And for the thread start: my mallard-runner hybrid drake use to sleep one head above the ladies (beside them, not really ON them) with balancing on ONE feet (left usually), head is inside his wings, eyes closed, other leg tucked on the side. Like a stork. Is it usual with domestic ducks? Or just the "wild genes"?