Yeah they're doing a fast controlled descent. Whether it's a low battery failsafe or a response to loss of control signal isn't clear but they're doing their best to land.

The first few look precipitous but you don't see them approach the ground, later in the video you see one that's coming down very fast and then makes a reasonable effort to brake when it gets near the ground.

Edit: Most of them are doing a fast controlled descent, a few seem to have just powered off and become rocks.

One of these drones in the second video is pretty much upside down as far as I can see.

Autorotation? Sorry I don’t know enough about drone aerodynamics, but it’s something seen in helicopters.

https://en.wikipedia.org/wiki/Autorotation

Not nearly enough energy in the rotor system of that kind of drone to manage an autorotation landing; and they lack a freewheeling system in any case.

Not sure about these drones, but on my toy drone I can absolutely cut the power and let the wind autorotate the rotors while it falls toward the ground. No need for a freewheel, since the unpowered electric motors spin freely (which isn't necessarily true for a helicopter's engine).

There's no collective so you can't "flare" for landing like a helicopter, but during autorotation the terminal velocity is still much lower than if the blades were fixed.

The drones in this video fall a lot slower though. This looks like controlled descent, not autorotation.

> but during autorotation the terminal velocity is still much lower than if the blades were fixed

it's not that straightforward, whether or not braking or freewheeling causes more drag depends on the prop.

[1] https://www.rcgroups.com/forums/showthread.php?3753127-Freew...

[2] https://www.peter2000.co.uk/aviation/misc/prop.pdf

Drones almost always use fixed pitch props which aren't capable of autorotation (in this sense anyway).