The Light Bulb Experiment

Excellent. That was the right answer!

The white light bulb is connected on both sides to voltage. Because of this the electric current has propulsion (= Antrieb) and thus it can flow; the white light bulb glows. The red light bulb, on the other hand, doesn't glow because there is no connection to voltage, no propulsion and thus no electric current.
The position of the red light bulb means that it is connected on both sides to the same electrical potential. Voltage means, however, that there is a difference in the potential.

Try to find a connection to the birds on the high voltage line. What does it mean for the bird?

If you manage to find that connection, then you are very close to the solution of the problem!