Over the last few years I have read, listened to people talk, viewed other web sites and observed people commenting on hunting shy birds and how they are trying to hunt in general.  Most recently I was viewing another site and this guy was describing how he was set up in a field covered in tall grass trying to call and could not figure out why they were not coming.  "DUH HU!" Because just like a turkey, they can see you from great distances.  Add angle to the scenario and multiple eyes, your done.  When he jumps up to shoot, the whole world sees him.  Take notice of this bit of info.  If a crow can see the ground all around you when he is flying to your set up, he can pick you apart.  This is why I am always expressing the importance of cover.  Overhead cover cures alot of this because, as I said, he can not see the ground and can not detect movement as well.  Blinds work well when you can not have overhead cover, just remember, the blind needs to be a least as high as you're armpits, so the blind creates an angle to block the view of the incoming birds until they reach shooting range.  As always, head to toe camo of some kind is needed for that extra edge.  Maybe they are not shy birds, just smart birds!