Gamebirds victory (16) – the 500m myth

DEFRA Secretary of State, George Eustice, says;

The negative effects of gamebird releases on protected sites tend to be localised with minimal or no effects beyond 500m from the point of release.

https://www.gov.uk/government/news/defra-concludes-its-review-into-releasing-gamebirds-on-and-around-protected-sites

I wonder why Mr Eustice thinks that. Might it be because that’s what was in a DEFRA Witness statement made by an anonymous civil servant?:

The Secretary of State has decided to put in place an interim licensing regime for 2021 releases of common pheasant and red legged partridge within European protected sites and within a 500m buffer zone around the sites.

para 24 of https://assets.publishing.service.gov.uk/government/uploads/system/uploads /attachment_data/file/931392/defra-witness-statement-gamebird-release.pdf

Later the DEFRA civil servant says:

… up to 25% of keepers could be impacted by a licensing regime that covers all European protected sites and a precautionary 500m buffer zone.

para 29 of https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/931392/defra-witness-statement-gamebird-release.pdf

And earlier it is clear that DEFRA think they have got this 500m threshold from Natural England:

Negative effects tend to be localised and studies (indicate minimal or no effects beyond 500m (on a precautionary basis) from the point of release. Most studies tend to be within 300m of the point of release or within pens thus there is no direct evidence of the effects at or beyond this distance. However, Natural England has concluded that effects beyond 500m are likely to be minimal because studies show that dispersal of birds tends to be less than 500m from the release sites and the negative effects in consideration are linked to the presence of birds.

para 11b of https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/931392/defra-witness-statement-gamebird-release.pdf

So did Natural England say that? It appears that they did say something like that;

Negative effects tend to be localised and the studies examined by the REA indicate minimal or no effects beyond 500m (on a precautionary basis) from the point of release, given the typical dispersal distance of birds from their release pen is less than 500m

Page 1 of https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/931396/defra-witness-statement-gamebird-release-exhibit3.pdf

And later Natural England says;

Though dispersal seems to be limited to less than 500m from the release site, there are no actual studies of the effects of gamebirds at or beyond 500 m from the release site, including effects on generalist predator populations, foraging behaviour, disease spread, competition for food, and eutrophication. Thus, there is scientific uncertainty about effects in the wider landscape. The reason that Natural England has concluded that effects beyond 500m are likely to be minimal is that studies show that dispersal tends to be less than 500m from the release sites and the negative effects in consideration are linked to the presence of birds.

Page 2 https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/931396/defra-witness-statement-gamebird-release-exhibit3.pdf

…which Natural England says is based on the Madden and Sage review. Before we go any further I can tell you that the 500m distance is not in the Madden and Sage review (as confirmed by J Madden when he didn’t answer a question on this blog the other day). So the 500m figure comes from Natural England. Interestingly they say there are no studies of the effects of gamebirds beyond 500m – that’s not the same as no impacts is it? No studies does not equal no impact.

Natural England also says that dispersal tends to be (not is, just tends to be) less than 500m from release sites. I wonder whether that is true?

I heard on Farming Today last week an interview with the GWCT’s Dr Roger Draycott where he said:

the majority of birds [Pheasants] don’t disperse more than a kilometre

BBC Radio 4 Farming Today, 2m 40s into a 3m 42s piece (I have the recording and I’ve checked)

… and he is the Head of Advisory of GWCT so I assume landowners hang on his advice and he gives good advice. And he says most Pheasants, not all Pheasants just most Pheasants, don’t go more than 1km – but that is twice as far as 500m, and it’s most Pheasants.

But Natural England says that studies show that Pheasants tend not to disperse further than 500m. I wonder what studies they are?

Might one of them be this study by Turner which does feature in Madden and Sage, page 77;

**Turner (2007) studied released pheasant at six sites over three years in southern England. Sites were large shoots with at least one full time gamekeeper, driven shooting and with birds released into pens located in woodlands. She tagged and tracked 486 pheasants in total, between 24 and 30 individuals for each site/year combination. She tested the effect of stocking density, which was experimentally manipulated between years within sites, on fate and dispersal (no significant effects were found). She radio tracked birds for around 5 months but dispersal was investigated using data from the first three months when tracking was more frequent. Overall, taking account of censored (lost) birds, 36 % of released pheasants were shot, 48 % died for other reasons (mostly predation) leaving 16 % still alive at the end of shooting (1 February). The overall average maximum distance moved was 913+82m. This is the average of the farthest distance each bird was recorded from the release point i.e. all other radio tracking locations were closer. Females moved further than males.

https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/931394/defra-witness-statement-gamebird-release-exhibit2.pdf

No it can’t really be that one can it, because that one says that the average of the furthest that these birds moved in three months was 0.9km and that is very different from Natural England’s ‘studies show that dispersal tends to be less than 500m from the release sites‘. How silly of Natural England to overlook that study from the Madden and Sage review that Natural England commissioned and presumably has read. I’ve read it, you can read it, maybe Natural England might read it again.

Maybe Natural England were thinking of this unpublished study by Beardsworth also in Madden and Sage?;

**Beardsworth et al. (in prep). continuously tracked the movements of 168 released pheasants at a site in Devon in 2017). Their location was logged automatically every 4s. They plotted the mean value for all surviving individuals of their max distance away from the centre of the release pen from mid-August to the start of the shooting season (October 1). Birds slowly dispersed from the pen but almost all birds remained within 500m up to 1 October.

https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/931394/defra-witness-statement-gamebird-release-exhibit2.pdf

But that study was based on just six weeks between mid-August and the end of September so it would be a bit rich to assume that Pheasants do not disperse further in the rest of their lives, especially when they are chased around the countryside in the activity of driven (yes, that means driving them) Pheasant shooting.

Maybe Natural England were thinking of this study by Sage et al. referred to in Madden and Sage (yes, same Sage)?;

Mean dispersal distance from release pen to February catch-site in 24 reared and released pheasants on a shoot in Cambridgeshire was 266 ± 41 m (**Sage et al.2001).

https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/931394/defra-witness-statement-gamebird-release-exhibit2.pdf

Yes that is less than 500m but it isn’t a measure of how far Pheasants go (as the Turner study above was) it’s a study of how far away they end up (they may have been to the moon and back before settling back close to home and note that this too only covers the period up until the end of the shooting season – not all the year. It’s also the study with the smallest sample size mentioned in these studies to date.

Have a look at the whole Madden and Sage report’s findings on Pheasant dispersal and keep in mind what they are measuring and over what time period (and how many birds are studied). I think you’ll find it difficult to concur with ‘studies show that dispersal tends to be less than 500m from the release sites‘ and impossible to regard this as a precautionary distance.

And then go on to read about how far RLPs go – they are adventurous little birds where ‘32% of birds dispersed more than 500 m, 5% more than 1 km and 1% more than 1.5 km’ but this was not the same as Turner’s measure above because it was average final per-bird dispersal distance.

So Natural England wasn’t very rigorous in their coming up with this dodgy 500m impact buffer zone: it’s not precautionary, it’s not exactly backed up by studies and it’s not measured over a long enough time to be useful. After the birds have been chased around the countryside and shot at, and then the survivors have had to range more widely to find food after the shooting season (when many estates stop feeding them because they don’t care about them any more (and don’t tell me the best practice guidance says ‘keep feeding after the shooting season’, I know that, but this is the shooting industry, remember)) we’d surely expect them to have travelled further than the studies above could measure. My conclusion: 500m is not the right number, it’s too low.

But there is a much more fundamental reason that 500m is not right and that is that it doesn’t remotely compute with all the impacts that need to be considered.

Let us take, for example, the whole business of high numbers of non-native gamebirds feeding the local predator and scavenger population. That impact has nothing much to do with how far the gamebirds go, it partly depends on how far the predators go (and not just how far, but where). Even if all Pheasants stay rigidly within 500m (which they clearly don’t) any Red Fox that eats a Pheasant is capable of travelling, even with a full tummy, much further than the 500m buffer zone. If lots of Pheasants travel 500m and get eaten by Foxes who then travel 2km and start gobbling up Curlews then the Curlews won’t thank DEFRA for a falsely-labelled-as-precautionary 500m buffer zone.

Let’s consider the impact of gamebirds on reptiles; let’s say Pheasants on Adders. We don’t know much about this; it definitely comes into the category of unproven but plausible. How might that work? Well, Pheasants gobble up Adders, particularly perhaps, young ones. imagine for a moment (it won’t take long) the unlikely situation where there is a wood with a Pheasant release pen in it and that wood is surrounded by a field (seems quite plausible) and that field is surrounded by a heathland SPA/SAC that is rich in Adders (that the heathland has Adders is plausible, that it is circular is implausible but it will help you think about it). The edge of the heathland is 500m from the centre of the wood. Now, even if the wood once had Adders if it has been heavily stocked with Pheasants for decades it doesn’t take many Pheasants to clear the wood out of Adders so that is past history. If the surrounding field is largely an Adder-free zone then there’s no problem there but once some wandering Pheasants get to 500m they hit the Adders and start having an impact (maybe particularly in late summer and early autumn when released Pheasant numbers are highest and Adders are active). The 500m buffer zone is pretty much irrelevant in this situation because all the present-day damage is caused by those Pheasants that travel over 500m and none of it, these days, by those that travel up to 500m so Mr Eustice would be wrong to say that ‘The negative effects of gamebird releases on protected sites tend to be localised with minimal or no effects beyond 500m from the point of release’ in this case. So he’ll need to increase his 500m quite a bit I think.

When I said at the top of the previous post:

There is a narrative developed by DEFRA and Natural England that the Madden and Sage review, and the bits that they didn’t look at, all combine to mean that any impacts of gamebird releases are limited to, and are known to be limited to, 500m from release sites. This is not true.

https://markavery.info/2020/11/05/gamebirds-victory-15-the-500m-buffer-zone/

… then I meant that it was not true. Pheasants and RLPs very often travel further than 500m and their impacts are often of a sort that cannot conceivably be assumed to be limited to 500m. It’s pretty obvious.

If you get this far then that was quite heroic of you and you must be quite interested in this subject – thank you.

Tomorrow I’ll ask you to do something to help you respond to the consultation on this matter when it arrives. It’s quite easy, requires very little knowledge and might be quite fun.

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