Top heavy rocks like that would be in a state of unstable equilibrium - they might balance for a second or two but if you even breathed near them they'd topple.
There is a clue on his website. The temperature was minus 5 C. The rocks look wet. I suspect there is a thin layer of ice between the rocks which overcomes the tendency to topple as long as they are finely balanced and held there while the ice forms. He does say if it's windy, they come down.
Drones are, in essence, flying autonomous vehicles. Pros and cons surrounding drones today might well foreshadow the debate over the development of self-driving cars. In the context of a strongly regulated aviation industry, "self-flying" drones pose a fresh challenge. How safe is it to fly drones in different environments? Should drones be required for visual line of sight – as are piloted airplanes? Join EE Times' Junko Yoshida as she moderates a panel of drone experts.