By chance, my review paper of Pheasant impacts was published at the same time as a BTO study to which I refer in the British Birds article: Pringle, H., Wilson, M., Calladine, J. & Siriwardena, G.M. (2019). Associations between gamebird releases and general predators. Journal of Applied Ecology.
Pringle et al. add another piece of evidence to the narrative that releasing 43 million Pheasants into the countryside each year has ecological impacts which government should look at. Previous work has shown that the UK has high densities of generalist predators and scavengers such as Red Foxes and Carrion Crows compared with other European countries. We also have a lot more Pheasants living and dying in the countryside, and dead Pheasants feed those generalist predators.
The BTO study shows that the comparison between the UK and the rest of Europe holds true within the UK too – places with loads of released Pheasants have higher densities of avian scavengers and predators.
I see that in the Guardian article last week, which covered both the BTO paper and my review paper, Jonathan Reynolds, head of predation control studies at GWCT, is quoted as saying of the BTO paper, ‘This study reports correlations only (ie not cause and effect) and they are very weak. We endorse the recommendation in the paper for more detailed and incisive research that looks at the hypotheses properly.‘.
Scientist says ‘more research needed’ shock! And just a quick pedantic point, when Jonathan Reynolds is quoted as saying ‘not cause and effect’ that is a bit misleading isn’t it? He might mean that correlations do not prove cause and effect (because they don’t) but he knows full well that the absence of correlations would be evidence against any cause/effect relationship and so the presence of correlations is evidence for cause and effect.
Presumably GWCT will be calling for an experimental approach to look at this question in more detail which ceases all Pheasant releases in large areas of the country for many years to see what happens compared with control regions? They will, won’t they?
GWCT have alluded to the possibility of increased predator numbers being caused by high Pheasant release numbers on their website but when more supportive evidence is added they have to downplay it because it would be very embarrassing for GWCT members and supporters if all those Pheasants and Red-legged Partridges were causing the high densities of Carrion Crows that GWCT members and supporters then had to kill under the general licences to protect Pheasants masquerading as livestock, wouldn’t it?
My BB Pheasant article puts it like this ‘Who should investigate the issues? The GWCT might seem the obvious organisation but has so far proved unwilling to tackle the most difficult issues, perhaps through fear that the information revealed might be akin to shooting its own funders in the foot.‘.
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Bloody well done Mark! This is one of quite a few ‘The Emperor isn’t wearing any clothes!!’ issues that as yet haven’t really been touched by our side but you and others are starting to with this one. Of course there’s also the point pheasant are predators in their own right – I’ve heard of video footage of them guzzling lizards which I haven’t located yet, wouldn’t be a stretch to imagine them doing that to wader chicks – AND the amount of land intensively farmed to produce the feed for them and RLP, AND the habitat that has been taken over by non native invasive planted out to give them cover. Known invasives such as cherry laurel and snowberry are still, unbelievably, being sold as such. SNH, Plantlife, the Woodland Trust etc have been contacted about this. There are a series of very big sticks to hit the mass bird shooting lobby with just sitting there waiting their turn to be used.
It’s certainly an extensive study with great data. The authors try to control for several potential confounds. However, the patterns and relationships are extremely varied and not always perhaps as intuitive or straightforward as some of the press coverage has implied.
Can you (anyone) suggest why some of the strongest positive relationships are seen for Jays (not known as scavengers and typically predating raised nests of woodland birds whereas pheasants/RL partridge generally nest on field margins/open ground), or why negative relationships are seen for magpies, or why some relationships are seen for pheasants but not RL partridge releases. Unfortunately, the authors provide little discussion of these points.
It’s also important to bear in mind the relative effects sizes shown here. The relationships are statisically significant, but taking Fig 3 as an example, it appears that the the effect of adding gamebirds is rather small. The difference between an area (tetrad of 10x10km) with 0 pheasants and an area with 1,000,000 pheasants is ~5 extra buzzards, ~1.5 jays, ~3 magpies, and ~2 ravens. This suggests that adding large numbers of gamebirds might increase populations of some avian predators, but not in great numbers, especially as few tetrads in the UK would host such large releases.
The relationships between predators and their prey are seldom simple – whole fields of ecology are devoted to exploring these. It can become even more complex in artificial systems, such as gamebird release, when prey availability takes the forms of a glut (when birds are released), and game keepers may deliberately target (legally or illegally) the predators most likely to benefit from the additional prey.
Given these caveats, I think it’s entirely reasonable for Jonathan Reynolds/GWCT to suggest that a more detailed study would be helpful. Recall that many gamekeepers might suggest that the negative relationship between songbirds and corvids is ‘obvious’ yet the current published data seldom supports this. For people opposed to shooting (or indeed any ecologist) to insist that it is ‘obvious’ that more gamebirds must lead to more predators, it might be salutary to pause and consider that in the glorious tangled web of the natural world and it’s networks of interactions, there are few, robust, obvious patterns.
Jo – thanks for your first comment here. I don’t think anyone said it was obvious did they? It is obvious that this possibility is a real one though, and that it needs to be taken seriously, and it is obvious that GWCT hasn’t done that so far. And nor has government. The Department of the Environment and Natural England are acting as though it is obvious that there is no effect – that seems an untenable position doesn’t it?
Personally I think the RSPB Roos et al. paper is more generally important than the Pringle et al. one – what do you think?
You’re welcome!
You question why GWCT did not publish this. I suspect that the GWCT realise that the BTO have an excellent dataset to answer such questions in their BBS/Winter Atlas data so perhaps felt that such analyses was better conducted by them, but I’ll let them defend their own research decisions.
I agree that DEFRA/NE might also be expected to conduct such work, but again, given that the BTO already hold such great data, it seems a poor use of scant resources for them to try to replicate that independently.
The Pringle et al paper has taken the first step to answer this important question and we should welcome that anyone has done such work. You seem to imply that Reynolds is ducking an issue by asking for further research to build on these findings. I suggest that this is exactly the right position to take given the, in my view, complicated results presented.
The Roos et al. 2018 paper was quite different from the Pringle et al one. It explicitly considered previously published studies to look at how predators may restrict prey populations (again a mixed picture emerged). It may have suggested that one explanation for high predator numbers in the UK was gamebird release, but it did not present any data to confirm this. The Pringle paper is important (more so than Roos et al in my eyes) because is actually presents new data to explicitly test this hypothesis. Perhaps the conclusions that arise from Pringle et al’s work are not as clear cut as the hypothesis about gamebirds/preds proposed by Roos et al, and make for a more nuanced narative if interpreted properly, but as I said, that’s ecology for you.
Jo – no, I didn’t question why GWCT didn’t publish this, I question why they haven’t done anything to address this issue scientifically. That’s not the same as the straw man you have raised and then answered.
Why didn’t Defra do it? Because they appear not to care a jot about such matters. They didn’t have to do it – they could simply have funded it. If you glance at the BB paper you’ll see that they were asked back in 2014 how they justified their stance on non-native gamebird releases and whether they were going to do any research on it and they said they had other priorities. They didn’t say they were sure the BTO would get round to it eventually. And the BTO study appears to have been funded by a private individual – the BTO don’t move very far without funding of analysis these days. Times are hard.
No I didn’t say taht Reynolds was ducking anything – but the organisation for which he works certainly is. Jonathan appears to have been given the task on belittling the Pringle et al. study. He didn’t say, as you just have, that it was a first step (I think it was about the third step) to answer this important question. The GWCT seems to have said ‘Somebody ought to do something about this but it must be better than the BTO have done, and although it is our members who are largely responsible for any downsides of Pheasant releases, which we accept there might be, we certainly aren’t going to do any studies’.
I still find Roos et al. the more stimulating paper. But that’s personal opinion for you.
Of course the interactions between species are extremely complex and unexpected, that’s nature in its incredibly complicated brilliance and wonder. The RSPB stop shooting fox at Abernethy and the decline in the capercaillie is at least arrested – it’s believed the foxes are putting a cap on pine marten numbers by eating them, now that’s a surprise. However, the very bottom line is that injecting an artificially reared biomass into the countryside, that according to Mark Cocker is equivalent to releasing a million Thomson’s gazelles every year, is going to seriously skew the populations of genuine wildlife and how the ecosystem such as it is functions. The exact details don’t obscure that, that we need to find all of them out is the point.
It would only be ‘reasonable’ if they were planning to do more research, to establish the environmental impact of such huge releases, before we go through this cycle again. They aren’t, though, so your defence of such a weak and disingenuous position calls in to question your own motives here. If you can’t see that the GWCT have a vested interest to bury the significance of pheasant/partridge releases and artificially enhanced mesopredator numbers, I have a bridge to sell you.
Well done, Mark!
I hope this may represent a turning point in awareness that the game killing lobby (the self-styled ‘doctors and nurses of the countryside’) are actually central to many of the processes wrecking it.
Should the GWCT finally get involved in research to look at the damaging effects of game killing, I wouldn’t trust a word they say or write. It needs an independent group – if you can find and fund one!
Funny how alien species like Mink are almost exterminated. as well as other species released either deliberately or by accident , but pheasants in their millions are okay. Of course its the tired old story of the rich being able to do what they like as they own the countryside and have the control of the Tory party.
Mark – Have you seen this research paper released earlier this year by the GWCT?
https://www.gwct.org.uk/game/research/species/pheasant/long-term-effects-of-pheasant-release-pens/
It examined the vegetation in pheasant release pens that were no longer in use for different lengths of time – up to 20 years. It found that the greater the density of pheasants in a pen the greater the impact on the nature of the soil and vegetation! In fact iirc the impacts from low densities of birds lasted 10 years but the high density pheasant pens still showed flora changes 20 years later! That’s a pretty major impact I would say!
lizzybusy – it is referenced in the BB paper, thanks
There’s no smoke without fire I suppose, but there are many reasons for the predator / prey
imbalance in this country, and it will take a lot of unravelling.
A large area, of mainly cattle grazed pasture, fodder crops, and unimproved ground , saw a three fold increase in Carrion Crow nests in about twenty years, with the nearest game rearing,
four or five miles over the horizon in one direction, and much further away in any other.
Quite often these nests would be in close proximity to farmhouses, a situation that would have been unthinkable to an older generation working the land, non breeding flocks of up to one hundred birds being observed on more than one occasion.
Some pasture improvement, and possibly a few more cattle ,being the only obvious changes in this time.
It is clear also, in my own mind , that gamebird releases can improve the first winter survival of Raptors such as Goshawks, and help to maintain high breeding numbers in spring.
Thrilling as this may be to some, you have to wonder about the possible effects on other prey
species.
What weight of evidence is required before the precautionary principle begins to kick in?
Or is that not how these things work?