The Military Wants A Way To Track Drones Flying Over Cities

What's the best way to track drones in the sky? There is no good way to track the drones in the sky. Passenger airplanes and helicopters report their flights to air traffic control, and even if they didn't, the vehicles are large and show up easily on radar, making it possible to keep an eye on them over land. Drones, especially commercial or hobbyist drones, are small enough to appear like birds on radar. Drones are also new enough that there isn't yet a system requiring them to broadcast their location to traffic control (or even, if such a system was devised, a guarantee that all small drones could power and obey it).