I know exactly the scenario you describe, and, if like me, you like to retrieve all the pigeon you shoot, there are a few things you can try.
First no-no is to tramp about among the vines every time you shoot a bird – even a dog in these circumstances can create quite a mess if you end up having a big day on the birds.
The first thing I look for are those thin patches of crop on which to set up.
Funnily enough pigeons themselves will often seek out these areas too because they are easy to get in and out of.
If the field has been particularly hard hit, you will find them close to favourite sitty trees.
Now you need to be disciplined and only shoot at birds which are right over the decoys, this means no fancy 50 yard crossers or speculative second barrels.
My second line of attack – which also calls for a lot of self restraint – works very well if you are close to the aforementioned sitty tree.
What you do is set the decoy pattern almost out of range of the tree, but build your hide directly underneath it.
You will be surprised at how many birds will flutter around the layout, and then head for the sitty tree to work things out.
You simply time your shot so that any shot birds drop into the hedge, or around the tree… making the final pick-up as easy as possible.