Magpies and crows to be culled to protect songbirds (1 Viewer)

MJB said:

So Adam, a long, illustrative answer to your query. In short, you are completely wrong to 'presume' at this early stage that a correlation between an increase in numbers and culling would represent a causal link. My reasons lie in that part of my motto, 'Biology is messy', and so almost always demand a long answer, no matter how many people want an instant 'yes' or 'no', and it won't always be the answer you (or I) want,
MJB

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I totally accept that this may very well be a complicated issue and might well not be as simple as an instant yes or no but come on if this cull was carried out and we quickly saw a noticeable increase in song birds then you cant tell me that we shouldnt read anything into that as it may just be total coincindence. Yes it may not be that simple and further reasearch should be carried out to find out more but if that was to happen i dont think its at all unreasonable to at least think that its a pretty good indicator of the sucess of the cull even if we need further evidence to call it proof.

If this cull is carried out and we see no change in song bird numbers or maybe even a drop in numbers I very much doubt we'll see a fraction of people criticising the results as we'll have the simple answer that most people want so they'll just accept it immediately without questioning it.

Adam W said:

...we'll have the simple answer that most people want so they'll just accept it immediately without questioning it.

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Adam, you are equally guilty of immediately accepting answers without questioning (think back about three weeks or so ). However, I don't think this is the issue.

Songbird Survival pick and chose research regardless of its validity and method and promote it to further their deluded goals. Should a limited cull of corvids be found to increase songbird numbers, you can bet Songbird Survival would parade it without caveat, not mentioning that it had yet to be reviewed, that the study results might be geographically limited or might be temporal, and certainly not mentioning if other studies might have found different.

And moreover, even if the removal of corvids does leads to an increase in songbirds, possibly short-term, possible not, does that then mean corvids should be removed?

If I were to be overly concerned with, for example, Skylarks, I could easily increase numbers on a local scale - I just chop down all the woodland on my land. Does it follow that this was a correct action to take? I could also attempt to kill every single predator that might possibly predate Skylarks to attempt to also boost numbers, would it follow that this was a correct action?

Jos Stratford said:

And moreover, even if the removal of corvids does leads to an increase in songbirds, possibly short-term, possible not, does that then mean corvids should be removed?

If I were to be overly concerned with, for example, Skylarks, I could easily increase numbers on a local scale - I just chop down all the woodland on my land. Does it follow that this was a correct action to take? I could also attempt to kill every single predator that might possibly predate Skylarks to attempt to also boost numbers, would it follow that this was a correct action?

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Obviously each situation is individual and needs to be treat acordingly but if it was found that reducing Corvid numbers helped increase other birds numbers then in my personal opinion then yes Corvid control would be a good idea(not removing them completely just controlling their numbers) so that we would then have increased populations of declining song birds whilst still retaining healthy populations of Corvids as well.

As for the Skylark example then of course that wouldnt be a sensible thing to do as it would obviously do more harm than good overall but i dont think the same could be said of the Corvid situation.

As I said each situation is different, to me reducing the numbers of common numerous Corvids to help increase numbers of decling song birds makes sense and seems reasonable.
On the other hand for example reducing already endangered species lets say Hen Harriers to almost extiction to increase already quite numerous Grouse to even higher levels doesnt make sense or seem at all reasonable, so if something works in one case no it doesnt automatically follow that its the correct course in all cases.

MJB said:

In terms of scientific ethics (not the ethics of killing or not killing), any organisation claiming scientific respectability has to start out from the position outlined above and not evade questions about methodoly and data. Songbird Survival decided not to accept findings from research they commissioned - that's their right - but their refusal to argue their case for their rejection on the grounds of flawed scientific or statistical method by citing appropriate published authorities suggests that their approach is less likely to be valid.

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The authority for the proposition that Songbird Survival 'rejected' the BTO's research findings is the paragon of scientific respectability known as Rod Liddle, as dutifully reported in Mark Avery's blog. Actually they did accept the findings. I, on the other hand, do not, and I'm still waiting for the authors of the relevant article to provide a meaningful response to the criticisms I've put forward.

I was under the impression that current story about the song thrush is that it's declined because of the spread of under-field drainage, so I'm interested in the narrow-spectrum pesticide theme. Can you provide a reference for this?

http://www.cpbell.co.uk
http://www.youtube.com/CultoftheAmateur

It is stupid how they are going to cull buzzards they hardly ever eat songbirds. Next thing you know peregrines and hen harriers will be culled, and then ospreys and eagles!

Lmc3598 said:

It is stupid how they are going to cull buzzards they hardly ever eat songbirds. Next thing you know peregrines and hen harriers will be culled, and then ospreys and eagles!

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No, they're not. They might want to (slight understatement there), but this research is into culling corvids.

The very badly written article gives a deliberately misleading impression with the words "The move could pave the way for birds of prey, including buzzards and sparrowhawks, to be culled in the same way." Who says it could?

Apodemus said:

No, they're not. They might want to (slight understatement there), but this research is into culling corvids.

The very badly written article gives a deliberately misleading impression with the words "The move could pave the way for birds of prey, including buzzards and sparrowhawks, to be culled in the same way." Who says it could?

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I read in a newspaper recently that they were going to cull crows and magpies and if a link is found then sparrowhawks and buzzards would follow. There was even a chart thingy with all the species involved in the cull, and buzzards were there and it said something about them being "villains". My area, the Scottish Borders, was one area mentioned where the culling was going to take place

Lmc3598 said:

I read in a newspaper recently that they were going to cull crows and magpies and if a link is found then sparrowhawks and buzzards would follow. There was even a chart thingy with all the species involved in the cull, and buzzards were there and it said something about them being "villains". My area, the Scottish Borders, was one area mentioned where the culling was going to take place

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No doubt some people would want that to happen, but saying that "if a link is found then sparrowhawks and buzzards would follow" is a big jump. Parlliament would have to vote on legislation amending the countryside and wildlife act and subsequent acts. At the moment, corvids can be culled quite legally, and this happens every day of the week. The two things are very different, and sloppy malicious journalism that blurs the line doesn't help the isssue at all.

Adam W said:

Come on if this cull was carried out and we quickly saw a noticeable increase in song birds then you cant tell me that we shouldnt read anything into that as it may just be total coincindence. Yes it may not be that simple and further reasearch should be carried out to find out more but if that was to happen i dont think its at all unreasonable to at least think that its a pretty good indicator of the sucess of the cull even if we need further evidence to call it proof.

If this cull is carried out and we see no change in song bird numbers or maybe even a drop in numbers I very much doubt we'll see a fraction of people criticising the results as we'll have the simple answer that most people want so they'll just accept it immediately without questioning it.

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Adam,
I said you would be wrong to presume that conclusion, not that we would not be able to read anything into it. Nor did anything I wrote that the conclusion to be drawn was that it was total coincidence. It would certainly be a likely indicator, pending further studies, but nothing about a single study can make the jump from correlation and causation in such a complex set of variables.

So much of our knowledge of bird behaviour and population dynamics comes from careful examination of the circumstances in which understanding has been achieved. However, much of present understanding when it was reached was counterintuitive at that time, often a kind of demolition of the 'everybody knows' view. That's not to say that the original views always are wrong. For example, amid the current tide of ornithological taxonomic revisions from hundreds of DNA-based studies, what is perhaps not apparent is that in quite a number of cases (but far from the majority), the morphological conclusions of Victorian-era taxonomists and of others subsequently have been found to deserve support!

Whenever I see the expression, "you can't tell me" in anyone's response, it gives me pause, for I then wonder if that represents the person's starting point. Just because you may see something with your own eyes, such as the complexities of a local artificial adjustment of population dynamics, does not mean that you have the solution, just a possible explanation. Of course, you may well be right in the long run, but I would suggest to those who wish to suspend their disbelief in the statistics of chance: don't bet on it!

However, I do not intend to put personality in the way of any discussion, and I always read your posts with interest. I think you are far from wrong to suggest that if the results of any cull study show an increase or no change that few will comment in detail, but it's my guess that most people will not have considered the self-same aspects that you and I have discussed.

There is a parallel here: the only way to tease out the bovine TB transmission pathology would have been to maintain a cull of badgers in high-incidence and TB-free areas, but a very understandable revulsion for 'killing for science' scuppered that. What degree of acceptance there would have been at the end of such a controlled trial is the subject for counterfactual history!
MJB

Fair enough MJB, I pretty much agree with what you've said there:t:

CPBell said:

The authority for the proposition that Songbird Survival 'rejected' the BTO's research findings is the paragon of scientific respectability known as Rod Liddle, as dutifully reported in Mark Avery's blog. Actually they did accept the findings. I, on the other hand, do not, and I'm still waiting for the authors of the relevant article to provide a meaningful response to the criticisms I've put forward.

I was under the impression that current story about the song thrush is that it's declined because of the spread of under-field drainage, so I'm interested in the narrow-spectrum pesticide theme. Can you provide a reference for this?

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CPBell,
Thank you for responding. Rod Liddle, IMHO, is certainly a 'loose cannon' to a degree that I am often as uncomfortable with his views when I tend to align with him as I am where I find no common ground.

Another thing that makes uncomfortable reading for me is the (to me) unnecessarily emotive use of language (or usage that is all too easily interpreted as emotive) in a discussion on a remote medium, such as this forum (no eye-to-eye contact, no inflection of voice, no body language). Without such day-to-day cues to help me put myself in other people's shoes, my default position in a forum is to be as neutral as possible.

Having followed on another thread your lengthy series of posts, many of which had paragraphs or sentences phrased expressing contempt or in a sneering fashion (my interpretation from repeated reading), my discomfort in addressing this aspect here, never having met, corresponded with, or even seen you, is likely to bias me in any attempt to respond to such phrases as 'dutifully reported' and 'in any meaningful way' in the context of your own sentences. So I won't.

Regarding the narrow-spectrum pesticide work, the report came out some time around 1997. I happened to have a European editing contract at the time, and I was housed at the BTO instead of somewhere in Europe, and I worked wherever there was a spare desk in an office. On the Song Thrush decline problem, probably in 1996, I can remember several people in one office holding many lengthy meetings to check and re-check methodology, analytical techniques and the like. I also remember the relief when a coherent and robust picture began to emerge. I'm not sure if the BTO Report led to subsequent papers in any journals, but that does often occur.

As to the present concerns about Song Thrush, I have only the sketchiest of knowledge, and so cannot comment helpfully about the sequence of work between then and now.
MJB

Adam W said:

Fair enough MJB, I pretty much agree with what you've said there:t:

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I dislike long posts and so don't like writing them either, but thanks for that! It was a pleasure to debate with you.
MJB

MJB said:

In terms of scientific ethics (not the ethics of killing or not killing), any organisation claiming scientific respectability has to start out from the position outlined above and not evade questions about methodoly and data.

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CPBell said:

Just to reiterate the main criticisms I’ve offered for the Newson study:

• Restriction of analysis to English data minimizes the variance of explanatory variables (change in abundance of predators that increased first in Scotland and Wales, then spread to England) thereby reducing the probability of finding significant effects.
  
• Deletion of individual terms from a linear model where they refer to explanatory variables that are likely to be highly correlated will inevitably result in a negligible (i.e. usually non-significant) change in model variance because of aliasing among the variables. It’s misleading to claim a lack of evidence for predator effects on this basis.
  
• The results of regression of predator change against prey change are unpredictable, even where there is a strong causal relationship, and the variable outcome will confound the detection of any underlying relationship.

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You're from the BTO? What a nice surprise! Over to you...

http://www.cpbell.co.uk
http://www.youtube.com/CultoftheAmateur

CPBell said:

You're from the BTO? What a nice surprise! Over to you...

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CPBell,
No, I'm not from the BTO. I've never been a staff member. I just happened to be given house room at the time for under 3 years. I wondered if in your response you would refrain from edgy comments, but to give you credit, you almost did.

Thank you for the three summary paragraphs. From my (fairly peripheral) involvement with mathematical modelling quite a long time ago in the 1980s using a purpose-built Norsk Data computer capable of complex, testable and modifiable simulations, my memory tells me that your paragraphs are couched in the appropriate language. However, they will be impenetrable to people without expertise. I make no pretence to have remained in any way current with progress and developments since.

However, when considering the canon of work in ornithology (and in related disciplines) on the general subject of predator-prey relationships, I find it less than plausible that a multiplicity of organisations have been so capable as to cover up without any leaks (no whispers at conferences or meetings) a plot to falsify or deliberately misinterpret data than to accept any simpler answer: that is, in this case, they are correct, or at least nearly so. If such organisations really were that capable, perhaps they should be running the security services, which are certainly not leak-proof.

Now, in the end, we may well find that you are right. Should that be the case, I would be among the first to congratulate you on your persistence, and perhaps we should leave it at that.
MJB

MJB said:

However, when considering the canon of work in ornithology (and in related disciplines) on the general subject of predator-prey relationships, I find it less than plausible that a multiplicity of organisations have been so capable as to cover up without any leaks (no whispers at conferences or meetings) a plot to falsify or deliberately misinterpret data than to accept any simpler answer: that is, in this case, they are correct, or at least nearly so. If such organisations really were that capable, perhaps they should be running the security services, which are certainly not leak-proof.

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Looks like a 'you can't tell me' argument 'IMHO'. By the way, for the most part I'm not accusing anyone of a plot, just of being not very good.

Also, since you like the edgy stuff so much, nice claim on the 'song thrush recovery strategy'. They must have responded to the waves of relief emanating from The Nunnery.

CPBell said:

Looks like a 'you can't tell me' argument 'IMHO'. By the way, for the most part I'm not accusing anyone of a plot, just of being not very good.

Also, since you like the edgy stuff so much, nice claim on the 'song thrush recovery strategy'. They must have responded to the waves of relief emanating from The Nunnery.

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CPBell,
I'll let others decide for themselves from your words and mine.
MJB

Top Gear have now come out in favour of a Magpie cull. It must be good idea then!!!!!!!!!

black kite 1964 said:

Top Gear have now come out in favour of a Magpie cull. It must be good idea then!!!!!!!!!

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Saw that! At least they were helpful in demonstrating that superstition is still with us...
MJB

Culling any native species requires some pretty extraordinary circumstances to be justifiable, and I really can't think of any situation where it would be so on a large scale or in the long term. We know that the numbers of some prey species are controlled by predator numbers, so killing predators would almost certainly lead to an increase in prey. I can't see how that fact alone would justify a cull, though.

If this cull merely boosts songbird numbers, that doesn't actually say too much. If it boosts certain declining species disproportionately, maybe it's time to look into ways to reduce nest predation, like improving the habitat or reducing any human perturbations that increase crow numbers artificially.

In the absence of any reason why crows might be more abundant than they ought to be, I'm not sure this study could justify any action, whatever the result.

LabradorDuck said:

In the absence of any reason why crows might be more abundant than they ought to be, I'm not sure this study could justify any action, whatever the result.

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Many corvid species have learned to be very effective commensals. Learning to take advantage of the abundant human waste can allow them to become superabundant (in the same way that some gull species have in parts of the world) beyond 'natural' or normal levels (whatever that means!).

There was a recent research project carried out locally into what factors were impacting on shorebird breeding success. Various culprits were expected - foxes, rats, cats, human disturbance, and avian predators such as ravens and gulls etc etc. While all of these occurred to varying degrees the big surprise was that ravens were the most significant predators. There was evidence that they seasonally adapted from scavenging around new 'beachside' housing estates to hunting out nesting shorebirds on adjacent beach areas during the breeding season.