Not as drastic as the mohawk helmet on your home page, but I use 3 or 4 (depending on which helmet) 300mm cable ties on my helmet and I have not been hit by magpies since.

They will still swoop, but they don't actually hit my helmet or head - I sometimes see their shadow or hear a flutter, that's all :)

I attach 2 cable ties towards the rear and sides of the helmet and point these outwards to protect my ears. I attach 1 or 2 more towards the rear and middle of the helmet, and point this/these upwards and slightly backwards.

I attach them in late August/early September and cut them off at the end of October/early November - depending upon magpie reports by other cyclists.

It's cheap and simple, and it does work :)