PETER THEOBALD says:
It was the late Archie Coats who experimented with decoys at roosting woods, and found that in certain situations the ploy would work.
He reckoned that pigeons needed to have fed in peace and were likely to return to roost early and in their own time.
Also, the decoys needed to be on the same type of crop which they had been feeding on all day.
In other words, there was no point setting up on rape if they had been feeding on clover.
The theory was that pigeons returning early, and not completely full, would be tempted to pop in for a top up.
I’ve got to say, the only time I have made it work to some degree, is outside a wood where some birds were in and out all day.
It is usually a waste of time if the flocks turn up mob handed half an hour before darkness.