But when it comes to working out whether such facilities are empty or full, whether the agents are stable or what type they are, analysts are often guessing.

BBC: Could US remove Syria chemical weapons?

They are concentrating on a study of stable isotopes - atoms of the same type but with different masses - and trace elements in the birds' feathers.

BBC: Feathers clue to warbler's travels

And from the looks of this demonstration, I think that this type of spherical drone is a lot more stable than a quadrocopter, thanks to its wings and gyroscopes.

FORBES: Japanese Defense Ministry Develops Spherical Flying Drone