How many gamebirds are released in the UK per year?

Claim

There have been several articles published about the recent DEFRA game bird review and legal proceedings. Each states an estimated number of game birds released per year in the UK, but this figure varies, ranging from an estimated 50 million to 60 million game birds (pheasants and red-legged partridges). What is the latest estimate and how accurate is it?

What the science says

True.

The most recent figure published in the peer-reviewed scientific literature for the number of game birds released is for 2016, when an estimated 47 million pheasants and 10 million red-legged partridges were released, a total of 57 million game birds.

Release numbers have been rising year on year, and updated estimates for 2018 using the same methodology suggest numbers have reached around 61 million, but this has not been formally published in the scientific literature.

However, as there are no formal records, these figures are estimates, not absolute numbers. All estimates have to be based on underlying assumptions and are only as accurate as the data that is available. Another recent paper, which is awaiting peer-review, used several different methods to arrive at an average estimate of 34.5 million gamebirds released per year in the UK.

Comes from:

Multiple papers have carried the story, with numbers varying from 50 to 60 million:

More than 50 million non-native game birds are released in Britain each year by shoots, of which there are around 5,000 nationally.” – The Times October 10th 2020

“…the increase in pheasants and partridges being released into Britain, from around 4 million annually in the early 1970s to an estimated 60 million today…” The Guardian October 30th 2020

More than 60 million birds are bred for shooting each year on Britain’s 300 game farms, in an industry that is worth more than £2bn a year, according to the Game Farmers’ Association.

At least 50 million captive-reared pheasants and nearly 12 million red-legged partridges are released to be shot – numbers that have risen sharply since the 1980s.” The Independent 31 October 2020

What the Science says – the fuller picture:

Estimating the number of gamebirds released in the UK is complicated because the number is not formally or centrally recorded. Therefore, to calculate the estimate, scientists have combined information from two different sources:

  1. The National Gamebag Census (NGC) is a voluntary survey scheme where up to 900 shoots across the country submit annual records of the number and species of birds that were released, and the number shot. NGC data do not allow estimation of overall UK numbers but do give an index to indicate the magnitude of change over time.
  2. A national survey was carried out by PACEC in 2004 (published in 2006), asking a sample of shooting providers for information on the number of various species that were shot, and the number of pheasants and partridges released.

The change over time in the NGC index from 2004 to 2016 was applied to the PACEC information to derive a likely figure for how many birds may have been released across the country in 20161.

This work gives us the most recent estimates published in the peer-reviewed scientific literature, namely an estimated 47 million pheasants and 10 million red-legged partridges released – a total of 57 million game birds in 20161.

Uncertainties in the figures used in the calculations translate into uncertainty in the end result, which is why 95% confidence intervals are given around the estimated number. This is a range, either side of the given estimate, that we can be 95% certain contains the actual number, if the assumptions underpinning the calculation are correct. For pheasants, this range was 39 million to 57 million and for red-legged partridges, 8.1 million to 13 million1. It is possible, statistically, to combine these estimates to get a 95% confidence interval for the sum of the two estimates, which tells us that the total number of game birds released lies approximately between 48.8 million to 67.4 million.

These figures for pheasants and red-legged partridges are the only ones published in the peer-reviewed scientific literature at this time. However, they are based on available information and involve a good number of assumptions during estimation. If those assumptions are wrong, both the estimates and their 95% confidence intervals will be wrong too. For example, it is suggested that the two PACEC surveys may have reported high estimates of the number of birds released, in which case any calculations that use these data will also be raised. Dr Madden from University of Exeter is looking at other ways of deriving estimates of numbers released and produced a working paper, although it has not yet been published or peer reviewed2. In this paper, 71 different estimates were made based on various sources of information including import controls, the Poultry Register, breeding outputs, observations of surviving birds and behaviour of shoots. A variety of estimates were made, and some were excluded as they were unfeasible. The most reliable estimates fall between 14.3 to 70.1 million, with an average of 34.5 million gamebirds.

Defra recently undertook a review of gamebird releases on and around European protected sites, examining various pieces of evidence. One exhibit (Exhibit EB2), Gamebird Review: Gamebird Numbers Paper published in October 2020, reported updated numbers for 2018, stating that there were 49.5 million pheasants and 11.7 million partridges released, producing a total of 61.2 million game birds3. The methodology behind these numbers is the same combined NGC/PACEC approach as used in Aebischer’s 2019 peer-reviewed paper described above1, but the updated estimates have not formally been published in the scientific literature.

Although the exact number may not be known, a more fundamental issue is the effect of releasing gamebirds on the surrounding environment. More information on this can be found in multiple recent reviews. This includes a paper published in 2020, examining the effect on habitats and wildlife4, a review by the RSPB5 and a report prepared by Natural England6. In general, positive effects tend to be linked to gamebird management while negative effects are associated with the release of the birds themselves. Some negative effects can be avoided by identifying and avoiding especially sensitive sites when releasing gamebirds. Higher densities of birds and not following good practice can lead to more negative effects.

References:

1. Aebischer, N.J. (2019). Fifty-year trends in UK hunting bags of birds and mammals, and calibrated estimation of national bag size, using GWCT’s National Gamebag Census. European Journal of Wildlife Research, 65:64 https://doi.org/10.1007/s103440191299x.

2. Madden, J.R. (2020). How many gamebirds are released in the UK each year? Preprint at https://www.biorxiv.org/content/10.1101/2020.10.22.350603v1.full.

3. SECRETARY OF STATE FOR THE ENVIRONMENT FOOD AND RURAL AFFAIRS. (2020). Exhibit EB2. High Court of Justice Queens Bench Division Administrative Court: 117.

4. Sage, R.B., Hoodless, A.N., Woodburn, M.I.A., Draycott, R.A.H., Madden, J.R. & Sotherton, N.W. (2020). Summary review and synthesis: effects on habitats and wildlife of the release and management of pheasants and red-legged partridges on UK lowland shoots. Wildlife Biology, 2020:112.

5. 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: Sandy, UK.

6. 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 Conservation. Natural England Evidence Review.

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