The wording of the 2009 licences in England and Scotland (but not Wales or Northern Ireland) requires that you satisfy yourself, not some official, that non-lethal methods of control are either ineffective or impractical.
It is left to your judgement to decide whether this is the case or not and in Wales and Northern Ireland you don’t even have to go through this mental rigmarole.
You don’t have to be protecting any particular crop at the time you go pigeon shooting.
The pigeon you shoot over the stubbles this week won’t be hammering the rape or peas the week after.
Wood pigeons cover a lot of ground and often move from one crop to another during the course of the day and those crops may be some distance apart.
With some exceptions it remains the case in this country that the prosecution must prove you have broken the law rather than that the accused should prove he hasn’t.
The licensing system acknowledges that woodpigeon are a pest, and provided you are sensible, you run no risk of prosecution.