In all seriousness, I’ve found that eggs work well near to decoys too.I already have a stack of crow decoys. When i used shoot them, i used to put egg shells and kitchen waste amongst them to lure them in. Always wanted to try mirrors but sadly that would be illegal.
The cardboard i had on rear window must have blew off in the wind last night as it was gone when i left to go to work at 3.00am and when i got home (you couldn't make this up) there was a huge crow sitting on rear wiper pecking at it. The front and rear nearside windows showed signs of crow attack.
Im really getting fed up now.