Thank you Conor. At 110 pages it will not be a fast read though I see a good number of pages are references.
One thing which jumps out at me immediately is the following
"We note that there are some coarse patterns relating to the effects of releasing and managing gamebirds. In general, effects that we might consider to be subjectively positive are usually a consequence of gamebird management activities (Associated Effects) and most effects that we might consider negative are caused by the released birds themselves (Direct Effects). We found reasonable evidence for physical disturbance of soil, nutrient enrichment of water and soil, reductions in nonwoody plants (especially those of conservation interest) due to damage or enrichment and reductions in abundance and/or diversity of at least some invertebrate species at or close to release sites. We found weaker, less or more ambiguous evidence that the released birds predated small vertebrates (reptiles), posed a direct competition to non-game species, spread disease to non-game species, influenced the genotypes of wild conspecifics (in England) or that their carcasses supported increases in generalist predators. Some negative Direct Effects have relatively straightforward management solutions and these are discussed in the relevant sub-sections....
...Working within the normal range of releases described in the papers we reviewed (a few hundred birds to a few thousand gamebirds in any one pen) it was a consistent result across studies that smaller releases had a reduced effect. This has been previously suggested and it forms the basis of the Code of Good Practice, advising that no more than 1000 birds be released per Ha of pen and that only around one third of woodland on a shoot be used as a pen. However, it is evident from the densities reported in the papers that, while average pen densities have in general gone down in recent years (presumably because pens have become larger), this advice is still often ignored."
So we have our own evidence, from our side, that this practice has a negative effect and that our self-imposed "best practice" is ignored!
And as a result of this being ignored, we are now facing licensing and the thin end of the wedge!! We should have acted sooner. We have the science and did nothing with it.