Today's blog is by Dr Jen Smart, Head of Species, England.

The RSPB remains neutral on the ethics of shooting, but we are concerned about the environmental impacts of its more intensive forms. During the last yearwe have consulted our membership and a wide range of stakeholders on their viewof gamebird shooting, and we have also reviewed the evidence relating to the impacts of gamebird shooting and associated land managementThis work has informed a wider policy review of RSPB’s position on shooting in the UK. We want to see a future where shooting, along with other land use, is compatible with the climate and ecological emergency.

We pride ourselves on being an evidence-based organisation, so a key focus has been to review the evidence for the impacts of driven grouse shooting and the large-scale release of non-native pheasants and red-legged partridges for shooting. This blog will focus on the latter of those reviews for one very good reason. While we have been conducting our review, of which I was one of the authors, a partnership between the British Association for Shooting and Conservation (BASC) and Natural England (NE) commissioned a review of the ecological consequences of gamebird releasing and management on lowland shoots in England, which was published online by NE in August. A really useful summary of this work can be found in this twitter thread. 

For ease of writing, I am going to refer to these reviews as RSPB or BASC/NE as the work was commissioned by these organisations, but I fully appreciate that the authors of both have different affiliations (RSPB = RSPB and a former RSPB scientist now based at the University of Kent; BASC/NE = Game and Wildlife Conservation Trust & University of Exeter).

Parallel reviews, same literature, same time-scale – different scientists 

The publication of two reviews of the same body of science, carried out independently and concurrently, provides ainteresting opportunity to compare the outcomes of bothIt is normal when a piece of science gets published that the authors identify knowledge gaps that need to be addressed with more science! It is also normal that most people are only interested in the conclusions of a piece of science and they may only read the summary to get a feel for conclusions and knowledge gaps. I am going to start by looking at the conclusions and knowledge gaps identified by these parallel reviews before considering the key points of difference  

There are a few areas where the scope of the two reviews differed: the BASC/NE review did not consider the effects of lead ammunition on wildlife or humans, or the social and economic dimensions of shooting, while the RSPB review did not consider the releasing of mallards. These topics therefore wont be mentioned further, because there are no comparisons to make.

Where do the conclusions align? 

  • Both reviews are based on a similar number of studies (RSPB scored the ecological impacts presented by 122 sources, BASC/NE considered 118 sources to be “highly” or “moderately” relevant). 
  • Both reviews are clear that releasing has increased rapidly and continuously since 1960. The best estimate we have of the numbers released in the UK each year is 47 (3957) million pheasants and 10 (8.113) million red-legged partridges, with 85% of the total occurring in England.  
  • A high proportion of the available literature and evidence is associated with positive ecological impacts that arise from the management associated with gamebird releasing. Such positive management includes habitat management and creation, especially improving arable land and woodland, but also legal lethal predator control. These effects impact on a wide range of taxonomic groups including plants, invertebrates, birds and mammals. 
  • The direction of some effects associated with gamebird releasing are open to interpretation, for example supplementary feeding of gamebirds may help support native birds and mammals overwinter but may also support non-native rodents and facilitate disease transmission.  
  • Some effects associated with shooting practices are negative such as disturbance or shooting of non-target species like grey partridges 
  • There is broad agreement that the direct impacts of released gamebirds themselves tend to be negative and include browsing of vegetation, predation of other wildlifegamebird faeces altering soil and water nutrients or spreading disease, but the extent and strength of evidence underpinning many of these impacts is more limited 
  • The direction of some direct effects is also open to interpretation. For example, gamebirds acting as food for generalist or protected predators could be perceived as positive or negative depending on your perspective. Both reviews conclude that gamebirds provide an important source of additional food for predators and scavengersHowever, whether this additional food resource is sufficient to allow predator densities to increase is less clear with so far only correlational evidence to suggest it might.   
  • There was consensus that direct impacts of gamebirds on native wildlife are generally greater where large numbers of birds are released but the scale over which these effects operate varies. For example, gamebirds as food for predators or disease vectors are likely to operate over larger scales than impacts of gamebird browsing, predation or soil enrichment which tend to occur on shooting estates or on neighbouring sites.

What are the key knowledge gaps? 

The range of key knowledge gaps identified by these reviews are listed with 1-7 identified by both, 8-9 identified by BASC/NE and 10 onwards by RSPB: 

  1. The lack of reliable, comprehensive fine scale data describing the size and location of gamebird releases is a significant barrier to assessing impacts of releasing at any spatial scale.
  2. Predation on vertebrates, especially amphibians and reptiles, by gamebirds. 
  3. Understanding the relationship between gamebird release and predator numbers and the consequences for predation of native wildlife. 
  4. Effects and the extent of transmission of disease and parasites carried by gamebirds to native wildlife 
  5. Impact of illegal persecution of native wildlife 
  6. Consequences of game management on native wildlife at estate and landscape scales. 
  7. Drivers behind the large-scale and ongoing increases in the numbers of gamebirds released (e.g. motivations of game managers).  
  8. There are several key knowledge gaps around whether the scale of different land management practises is related to the scale of gamebird releasing for exampledoes the intensity of predator control or the area of woodland creation or management increase in a linear or non-linear way with the number of birds released 
  9. Effects of disturbance by game managers or guns’ (shooters) 
  10. Potential competition for food and space between gamebirds and native wildlife 
  11. Effects of supplementary feeding, medication in gamebird feed and misuse of rodenticides on native wildlife 
  12. Unknown extent and intensity of legal predator control on the majority of gamebird releasing sites 
  13. Extent of accidental shooting of other species during non-native gamebird shoots.  

What are the key differences between the reviews? 

The key difference between the reviews is in the methods used to assess the literature.  

The BASC/NE review used a rapid assessment method to categorise the literature according to study quality (highly relevant = treatment versus control or relationships across gradients in release or scalemoderately relevant = quantitative assessmentweakly relevant = qualitative assessment). framework was used to visualise the direct effects of gamebirds (e.g. foraging, competition, disease), the associated effects of the actions of those releasing the gamebirds (e.g. land and predator management, shooting) and the indirect effects on the environment and native biodiversity.  

The RSPB review identified 6 primary and 19 secondary themes. The primary themes were game estate management, shooting practises, illegal persecution, direct impacts of gamebirds, disease transmission to wildlife and impacts on predators and predation. Ecological impacts were scored on a scale from -2 to 2 accounting for the direction, strength and reliability of evidence with scores of +/-2 indicating strong, reliable evidence for a population-level impact, +/-1 indicating weaker evidence or a more local impact, and 0 indicating no evidence of impact. Using a statistical approach, this review analysed scores across themes to establish the weight of evidence for positive and negative effects.  

To summarise: 

It is re-assuring that these reviews came to broadly similar conclusions. Numbers of gamebirds released in the UK each year continue their inexorable rise, with the current scale of releasing unlikely to be environmentally sustainable. There is clear evidence of positive impacts of gamebird management on the range and quality of mainly woodland and farmland habitats. There is growing evidence of potentially serious negative ecological impacts of gamebird release, and further research funding is urgently needed to address these growing concerns. 

The hope now is that the various stakeholders in this issue can work together to agree, prioritise and plan how to resource the filling of the most important knowledge gaps. Who should pay for this research is an interesting question – taxpayer, shooting industry or NGOs? There is also an urgent need for stakeholders to work together to use the available evidence to agree what sustainable gamebird shooting might look like in future. There will no doubt be a range of views from stakeholders about how to address these environmental concerns but at our recent AGM, the RSPB has outlined our views which you can read here.

Madden J.R. & Sage, R.B. (2020) Ecological Consequences of Gamebird Releasing and Management on Lowland Shoots in England: A Review by Rapid Evidence Assessment for Natural England and the British Association of Shooting and ConservationNatural England Evidence Review NEER016. Peterborough: Natural England. 

Mason, L.R., Bicknell, J.E., Smart, J. & Peach, W.J. (2020) The impacts of non-native gamebird release in the UK: an updated evidence review. RSPB Research Report No. 66., RSPB Centre for Conservation Science RSPB, Sandy, UK.

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