If there was a single answer to this question it would be – What ever gets you results!
Seriously, there isn’t a magic answer to setting out decoys that always gets results but there are a few very fundamental things to consider.
Decoys will only draw pigeons in when they are already in the area. I know it sounds daft but some folks seem to think they can draw pigeon into an area because that is where they have permission to shoot. Wrong. Pigeons go where pigeons want to go not where you are allowed to shoot. It is against the General Licence to create a need to shoot pigeons because you have drawn them in to an area. The General Licence is an exclusion to the general ban on shooting birds and mammals based on the need to shoot pigeons as a last resort. Drawing pigeons into a shootable position in an adjacent field to where they are doing damage but where there isn’t a safe direction to shoot them would be fine.
So decoys should be set out where pigeons are already evident so you can get them into range or close enough to their flight line to get them to deviate and come to you for a look. If pigeon are hitting a part of a large field go to where they are if possible. They are choosing that part of the field for a reason they understand even if you don’t.
A large number of shell decoys on the ground will look like a huddle of happy pigeon so probably forget about rotaries and fancy bouncers. A dozen decoys isn’t a flock. Fifty decoys less than 1.5m apart looks more like it and weighs less than a pigeon magnet and a thumping big battery.
If you have to grab the attention of a passing pigeon then movement and flying decoys may well be needed but put them where they can be seen from a way off. Watch they aren’t blotted out by a high hedge or trees and that they contrast with their back ground. A few extra decoys on the top of a hedge or a small tree may attract pigeon that aren’t intested in ground feeding but are ready to lay up for a few hours.
Almost all pigeon on the ground face into the breeze otherwise they get cold and ruffled by the wind. Do the same with your decoys with just a few at odd angles. Most guides say to make a horseshoe shape so bird drop into the middle of the pattern but I’m not 100% sure about that, I haven’t seen pigeons in a horsehoes pattern ever.by