Does a truck carrying birds get lighter when they take off? New bird measuring kit solves physics riddle

Previous tests showed that the weight would stay the same — but new precise measurements show that it would actually fluctuate

Pigeons fly outside St. Stephen's Cathedral, Vienna (JOE KLAMAR/AFP/Getty Images)

A new super-sensitive device could solve mysteries about how birds fly.

Scientists at Stanford University have made a device that can precisely measure the weight of birds in flight, and the force created by each wing flap.

It was developed to help the team measure the flight of tiny drones.

But it also helps solve a mystery — whether a truck carrying birds would get lighter when they took off.

The question was put to the test on American TV show Mythbusters, by putting a truck full of pigeons on a scale and getting them to fly. They guessed that was probably because the air being displaced by the birds’ wings was pressing down on the box.

While that’s mostly correct, the precise measurements of the new device shows that the box would change as the birds flap their wings.

Measurements from one bird showed that they actually make twice the lift when they flap their wings down, so that they don’t have to lift their weight when the wings come back up again.

If the box had only a few birds in it, that would mean that it the weight would fluctuate as they flapped. If more birds were in the box, the weight would probably even out, as they all flapped their wings at different times.

The sensor will be used to test small drones, and fine tune their flight.