Can anyone more knowledgeable explain how this works?

Is it harvesting energy from the magnetic field (via induction), or does it extracts its energy from the electric field instead?

And does the drone just happen to land on the power line for saving energy while doing so, or is the contact necessary somehow?

Balisor[1] usually uses capacitive coupling, but it require a long parallel cable.

Some lamps do use induction, like this one[2].

I guess it uses induction looking at the drone, it also works with an open coil.

[1]: https://en.wikipedia.org/wiki/Balisor

[2]: https://www.delta-box.com/en/marking/bht-marking-light-for-h...

I would guess that its just a coil thats near the cable. however I can't imagine its actually that much power, as the field isn't that strong.

_but_ at 33kv, you start to get corona discharge, which gives you a potential difference, so that might be the mechanism they get power.

(thats a wild guess. )

Edit I did some more digging, induction appears to be magnetic induction, long cables do produce a magnetic field, but not that much (unless you put it in a coil)

Capacitive coupling is much more effective at high voltage.