Sparrowhawks responsible for House Sparrow decline says scientist (1 Viewer)

[AlfArbuthnot]

Yes but my broader point here is that you and others are seeking some kind of infallibility from Dr Bell's methods where this does not exist in numerous other studies.

Not at all. I have been very clear that what I have been asking for is an admission that the work isn't conclusive, and the points raised about the methods were a significant source of potential error. That is all.

My example of bird ringing sites still stands - the habitat codes used by ringers to assign habitat are broad and qualitative (e.g. urban, semi-rural, rural), yet these data are used, to take a hypothetical example, to show that species A is increasing/decreasing in Habitat B. The classification of habitat is a subjective qualitative decision made by the ringer - ringers do not, as far as I am aware, undertake NVC surveys of their ringing sites.

Yes, they are subjective. But I haven't seen any studies where they have been used in sample sizes of less than 10 and as an either/or category, which would make the study extremely sensitive to mistakes in classification. But this is how CPBell used his data. He could have very easily quantified urbanisation (which he clearly defined) to an EXACT percentage. But he didn't, he just guessed. If he had very large sample sizes then it would have evened out a bit, but CRUCIALLY, he didn't. Which means that his pattern of colonisation and decline is based on VERY FEW data points, and some of those are highly likely to be wrong. Not just a bit wrong, or slightly wrong, but the TOTAL OPPOSITE of what he thinks they are, because he only used two classifications (so if it wasn't classed as urban, then it had to be classed as rural). This is a very big problem for him, because his model is so sensitive to this error.

OK, but if AN Other author were to come on this forum and allow 2+ years of every Joe having a pop, do you not think that their position would harden?

It depends on their personality, I would suppose. They could either convince the majority of others that the questioner was wrong, by providing evidence, or they could accept that the poster may have a point. have you seen any evidence of that? Or just patronsing attacks and pithy dismissals?

or would they simply say 'OK, you are a regular contributor to Birdforum, you can clearly measure the 3rd primary length on a dodgy photo and deduce subspecific identification, you clearly know best, fair do's!'. Come on.

Of course not. But why not just tell us what the sample sizes were? Or how the maps were classed? Are they such dangerous, inappropriate questions?

As an aside, my point about sparrowhawk vs cats may have been flippant, but if a paper entitled 'Cats responsible for Sparrow declines' had been published, I would bet my last pound that no-one on here would have given it such a mauling and indeed would have sagely nodded their heads and said 'Of course, we knew it all along'.

If you look back a few years to studies on the potential effect of grey squirrels on birds, there were a few headlines blaming them for various declines. But BTO and RSPB looked some more, and then freely admitted (in various papers), that there is basically no evidence that squirrels are any sort of problem for any bird. So people who are seriously interested are not as biased as you may imagine. They are mostly interested in what is true, and what can be proven.

It is precisely because this paper goes against received 'wisdom' that it is seen as fair game.

I don't think so. I think it is a heady combination of the paper being used as 'proof' by extremists (when it isnt strong proof), CPBell's public attacks on other studies and researchers in an apparent self-publicity drive on the internet, and also the lurid personal aspects which then became relevant (such as scientific credentials, experience, work history, and why the BTO might not want to deal with CPBell for reasons other than corruption). As long as the outlandish claims are being made about the strengths of the study, the BTO, the RSPB, and corruption in conservation, I imagine that people will counter them.

I would urge you, bluechaffinch, to note that CPBell has spoken with exteeme vitriol about people who are not involved in this thread, such as Peach, Vincent, Newton, Davey, Chamberlain, the BTO, the RSPB; so it is not as if CPBell has been goaded into negative and personal attacks as a form of defence to posters on BirdForum. He is vitriolic regardless of how people post on this forum, and to people who have never posted a word.

 

[Nightranger]

Well, my reading of this thread is that DR Bell's previous employment issues were raised pretty early on in the debate, whilst he was in fact being rather courteous and other posters were praising him for his openness. I wonder how other members would feel about having their character slandered by strangers online, regardless of whether this info is in the 'public domain'. Someone had to go digging...

BC, I nearly had my career terminated early as a result of the activities of one person and I am sure those events still haunt the dark shadows of my career even today. Hey, you know what! I have moved on! We all make mistakes and heck, some of us genuinely have to deal with vindictiveness. If Dr Bell had real concerns about the way he was/is being treated, he would take legal action. I have said on this thread that I have severe personal misgivings about the RSPB but that is a private matter and even if I should choose to take legal action, I would never air it on here because it is not in the public interest.

Yes but my broader point here is that you and others are seeking some kind of infallibility from Dr Bell's methods where this does not exist in numerous other studies. My example of bird ringing sites still stands - the habitat codes used by ringers to assign habitat are broad and qualitative (e.g. urban, semi-rural, rural), yet these data are used, to take a hypothetical example, to show that species A is increasing/decreasing in Habitat B. The classification of habitat is a subjective qualitative decision made by the ringer - ringers do not, as far as I am aware, undertake NVC surveys of their ringing sites. My own garden ringing site is in a village, yet the habitat code for 'Rural' states that this means farmed land with scattered buildings: my small village does not fit this description yet neither does it fit 'semi-rural.

Some of this is fair enough BC but it has very little to do with Dr Bell's studies. It is very clear if you read the paper that this was an urban study (see Alf's comment re: my earlier post) and furthermore a model was produced to either pre-empt the data or in hindsight (I confess, I am not clear on this one) to confirm it. As I have said before and I am saying long after I wanted to let this thread die, the model is the biological equivalent of the two body problem in physics. Dr Bell has gone on to talk about house sparrow declines in both urban and rural settings on this thread and if you are aware of predator - prey relationships, this is an assumption, it invalidates so much of the conclusions in his work insomuch as the assumption itself is not even discussed.

Failing to discuss other research is very poor science no matter how you dress it up but criticising opposing ideas because they do not fit with a preconceived notion (as seems to be the case here) is about as valid as the science in the film, Slipstream (Mark Hammill). In other words, entertaining but not much else.

OK, but if AN Other author were to come on this forum and allow 2+ years of every Joe having a pop, do you not think that their position would harden? or would they simply say 'OK, you are a regular contributor to Birdforum, you can clearly measure the 3rd primary length on a dodgy photo and deduce subspecific identification, you clearly know best, fair do's!'. Come on.

BC, there is a point in life where we could all benefit from standing back and saying I was wrong. Dr Bell has long passed that point and I think you know it too. I admit that sometimes even the most humble of us find it hard to admit where we went wrong but again, it is a good place to be. I have learned more in my life by stopping to listen to other opinions than I ever could hope for by trying to hold on to my pride. This is a simple acceptance of the fact that 'whilst I may be good at some things, I am not an expert in everything'. I have been a birder for 30+ years but just today I was happy enough to ask for help with a gull ID even though my instincts had already pointed me more or less in the right direction.

It is precisely because this paper goes against received 'wisdom' that it is seen as fair game. This attitude colours all subsequent discussion on the matter, until we reach a point whereby the 'true' reason for it being wrong is down to methodology: this may or may not be the case, but I would expect at least a little humility from those against the findings in admitting that the only reason they are so worked up is down to inherent prejudices towards any notion that it is not humans who are responsible for bird declines

No worries if Dr Bell is confident with his methodology but surely then, his defence would be impecable? Humility works both ways BC and it is a bit pointless to expect humility from people who have provided pointers and asked questions that have not been answered, don't you think? Alf has already answered the point about human responsibility for bird declines but to be honest, I am struggling to find many examples of a non-human cause. The potential extinction of the ptarmigan and breeding snow buntings in the UK are possible examples but that all depends on your belief in climate change and/or whether it is also caused by humans.

 

[Nightranger]

I would urge you, bluechaffinch, to note that CPBell has spoken with exteeme vitriol about people who are not involved in this thread, such as Peach, Vincent, Newton, Davey, Chamberlain, the BTO, the RSPB; so it is not as if CPBell has been goaded into negative and personal attacks as a form of defence to posters on BirdForum. He is vitriolic regardless of how people post on this forum, and to people who have never posted a word.

What I find amazing Alf is that CP is unwilling to even acknowledge the existence of J Denis Summers-Smith. I have read some good monographs on birds in my time but the house sparrow book is one of the all-time greats. I will even balance this by saying that Summers-Smith's monograph of the tree sparrow is nothing like as good (not that it is bad). I think even CP has enough humility to realise that someone who has spent his life (or a good bit of it) studying one species just might trump someone who has gathered a bit of data (and I mean - a bit) then produced a computer model. Of course, I may be wrong and J Denis may be on here in the next few weeks to tell us how the RSPB and BTO 'have got it wrong' about house sparrows.

 

[MJB]

Bluechaffinch,
Re "having their character slandered by strangers online", slander is slander only if it's untrue, but since slander is a malicious verbal statement that being false or malicious, harms a person's reputation, what you probably meant was "libelled by strangers online". Libel, covering written and broadcast statements, also has to be untrue, but similarly is false or malicious in character.

I leave it to you to decide which, if any, of the statements made by CP Bell or anyone else on this thread tend towards, or comprise libel (but you may need legal advice as to the soundness of your decisions), and then consider if there is any equivalence.
MJB
PS An annoyed reaction does not constitute malice in itself...o

 

[JTweedie]

And hopefully libel reform will be successfully enacted to stop people closing down free speech or opinions that are not to the complainants taste.

 

[MJB]

And hopefully libel reform will be successfully enacted to stop people closing down free speech or opinions that are not to the complainants taste.

Until the scandal of the banks manipulating interest rates broke, I might have suggested no chance in England, given the cascade of recent political decisions, but now, it might be a race between Westminster and Alex Salmond to be seen as the more reformist!
MJB
PS Aye, right...:-O

 

[CPBell]

Further to the BTO’s disinformation leaflet on sparrows, I’ve just picked up this little gem from their ‘Birdtrends’ page:

“Negative correlations between indices of Sparrowhawk presence during its recolonisation of the UK and House Sparrow abundance from the Garden Bird Feeding Survey have been interpreted as evidence that increasing predation rates are depressing House Sparrow populations (Bell et al. 2010). However, more sophisticated analyses of large-scale and extensive national monitoring data provide no evidence that House Sparrow population declines were linked to increases in Sparrowhawks (Newson et al. 2010).”

Note the subtext of ‘it’s just a correlation’ in their description of my paper, and the ludicrous description of Newson’s awful paper as ‘more sophisticated’. What they’re saying to Joe Public is ‘don’t worry, this is all above your heads but we know best, so keep on trusting us (and handing over the money)’. The rest of the entry is nothing more than textbook exercise in spin, and it can’t help but raise the question as to whether we can really trust anything this partisan and politically-driven organisation says about birds.

Some responses to earlier posts.

Now we have BTO research which suggests that HS are actually increasing - so which way is it? Are these various reasons now not an issue? Are there no more plastic soffits and fascias being installed? Are our gardens all messy because we have no money to tend them well due to the downturn? When exactly did these factors stop being an issue? Is it the dreaded cats???

I find it frustrating that on the one hand people are more than happy to go to town on Dr Bell's paper and espouse various factors which are far more likely causes for HS declines, and yet when BTO research shows that HS are increasing fail to acknowledge that maybe this flies in the face of the 'all is doom' hypothesis. Can't have it both ways!

It’s going to be very easy to attribute sparrow recovery to any or all of these factors, simply because there was no evidence that they were relevant in the first place. Command of the narrative is all, and we can see this changing, because as every politician, business executive and con-artist knows all too well, it’s crucial to move swiftly on from failure. The BTO’s garden birdwatch leaflet narrows the horizon back to the 90s, and indulges in hand-waving about short-term fluctuations since then. The catastrophic decline of sparrows and other birds the 1970s is thereby relegated to a footnote in history, since it’s now a potential embarrassment rather than a cash cow. We also currently have a repeat of the London sparrow survey which might well reveal a modest recovery, contributing to the new ‘why are sparrows recovering’ narrative. No doubt the usual suspects will not be slow in coming forward to take credit.

The majority of the posts against Dr Bell have been questioning the validity of his methodology, his sample sizes, his designation of site type etc. The fact that he NEVER responds to such questioning, but seriously reduces the value of the debate....

The only thing I never respond to is Alf Arbuthnot, because following our lengthy exchange in March/April, it became all too apparent that (i) he is grossly abusive (ii) his responses rapidly degenerate into meaningless babble. You, on the other hand are merely snarky and evasive, which is why there is potential (at the margin) for meaningful debate (which you always lose). So what is it exactly about my methodology, sample sizes and designation of site type that you have a problem with?

You have lost me on this one, you are pouring scorn on Dr Peach's work now? However, if you really want scientific credibility then I suggest that you produce a better critique of Dr Peach's work than simply using a phrase such as 'dodgy PCA analysis' and tell us why it is dodgy. Incidentally, I know Will Peach and he is not only a top scientist, he is also a very nice chap.

PCA and other multivariate techniques are the friend of the pseudoscientist. The data rarely conform to the statistical assumptions of the technique (and certainly don’t in this case), so can appear to throw up all kinds of random relationships, one of which might be just what you’re looking for. If not, you can just leave it out and no-one is the wiser. Even assuming the PCA axis used expresses some meaningful environmental gradient connecting 100% concrete at one end with 100% deciduous shrubs at the other, there will be so many covariates that it is impossible to draw any meaningful inference from a relationship with sparrow breeding success.

It is 'received wisdom' that cats kill hazel dormice and therefore any new development site will have to take measures to ensure that cats do not enter dormice habitat (or potential habitat). This usually takes the form of a planning condition requiring certain fencing specs or, I kid you not, a Section 106 agreement preventing homeowners keeping cats. Is this based upon sound scientific evidence? No. The only study on cat predation - 'What the cat brought in' - found that something like 0.003% of catches were dormice. Yet the 'belief' that cats must kill dormice persists (despite them being arboreal for most of the time) and impacts upon interpretation of planning policy.

You make an important point here, which elides very well with the issue of narrative that I referred to above. Conservation legislation, which supports a burgeoning industry, is largely based on the standard conservation narrative with its roots in (non-scientific) natural history and the ‘back-to-nature’ movement. It’s crucial, however, that regulation is seen to have the imprimatur of science, which means that science is managed to produce results that support the imposition of ever greater regulation. This is why studies like mine (and your dormouse example) are so threatening – they undermine the rationale of established conservation policy, and the status and income of those responsible for, and dependent on such policy. The unfortunate side effect of this is that scientific enquiry is stifled, and conservation itself is compromised, since only science can produce real solutions.

What I find amazing Alf is that CP is unwilling to even acknowledge the existence of J Denis Summers-Smith.

Sorry to break this to you, but it’s the other way round. JDSS was one of the first people I send the paper to when it was in press, and he sent back a critical reply with the caveat that ‘I hope we can disagree and still be friends’. Encouraged by this, I responded to his criticisms and we exchanged a series of mails, during which he gradually became more tetchy, and ultimately cut off the correspondence. I would be happy to publish this, but he has refused to approve it, so I won’t. His unwillingness to debate the issues has not prevented him from repeatedly reviewing my work in a hostile manner – on one occasion the editor of British Birds agreed to disregard one of his reviews since it was so obviously biased. JDSS also refused to release the review he wrote for the first submission to the Independent competition.

On the whole his interventions in the sparrow debate have not been very well judged or enlightening – witness the interventions by Klaus Witt and Crick & Robinson in British Birds (89:146, & 96:306-7). The obsession with diesel and MTBE may be more of a penance for a lucrative career in the petrochemical industry than anything else.

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

 

[AlfArbuthnot]

Allow me to paraphrase for the benefit of those low on time and alcohol (which you'd need to get through it!):

According to CPBell:

The BTO are liars, who are after your money.
Nobody else has done a study worth reading.
Nobody else is up to the level of CPBell's debate.
He is being picked on by people nowhere near as clever as he is.
he would answer Jane Turner but doubts that she'd understand.
The whole of conservation science is corrupt and desgined to deliberately perpetuate a hippy myth.
CPBell bravely wishes to smash down this house of cards, and save us all from ourselves and our ignorance.

I think that covers it.

Further to the BTO’s disinformation leaflet on sparrows, I’ve just picked up this little gem from their ‘Birdtrends’ page:

“Negative correlations between indices of Sparrowhawk presence during its recolonisation of the UK and House Sparrow abundance from the Garden Bird Feeding Survey have been interpreted as evidence that increasing predation rates are depressing House Sparrow populations (Bell et al. 2010). However, more sophisticated analyses of large-scale and extensive national monitoring data provide no evidence that House Sparrow population declines were linked to increases in Sparrowhawks (Newson et al. 2010).”

Note the subtext of ‘it’s just a correlation’ in their description of my paper, and the ludicrous description of Newson’s awful paper as ‘more sophisticated’. What they’re saying to Joe Public is ‘don’t worry, this is all above your heads but we know best, so keep on trusting us (and handing over the money)’. The rest of the entry is nothing more than textbook exercise in spin, and it can’t help but raise the question as to whether we can really trust anything this partisan and politically-driven organisation says about birds.

Some responses to earlier posts.



It’s going to be very easy to attribute sparrow recovery to any or all of these factors, simply because there was no evidence that they were relevant in the first place. Command of the narrative is all, and we can see this changing, because as every politician, business executive and con-artist knows all too well, it’s crucial to move swiftly on from failure. The BTO’s garden birdwatch leaflet narrows the horizon back to the 90s, and indulges in hand-waving about short-term fluctuations since then. The catastrophic decline of sparrows and other birds the 1970s is thereby relegated to a footnote in history, since it’s now a potential embarrassment rather than a cash cow. We also currently have a repeat of the London sparrow survey which might well reveal a modest recovery, contributing to the new ‘why are sparrows recovering’ narrative. No doubt the usual suspects will not be slow in coming forward to take credit.



The only thing I never respond to is Alf Arbuthnot, because following our lengthy exchange in March/April, it became all too apparent that (i) he is grossly abusive (ii) his responses rapidly degenerate into meaningless babble. You, on the other hand are merely snarky and evasive, which is why there is potential (at the margin) for meaningful debate (which you always lose). So what is it exactly about my methodology, sample sizes and designation of site type that you have a problem with?



PCA and other multivariate techniques are the friend of the pseudoscientist. The data rarely conform to the statistical assumptions of the technique (and certainly don’t in this case), so can appear to throw up all kinds of random relationships, one of which might be just what you’re looking for. If not, you can just leave it out and no-one is the wiser. Even assuming the PCA axis used expresses some meaningful environmental gradient connecting 100% concrete at one end with 100% deciduous shrubs at the other, there will be so many covariates that it is impossible to draw any meaningful inference from a relationship with sparrow breeding success.



You make an important point here, which elides very well with the issue of narrative that I referred to above. Conservation legislation, which supports a burgeoning industry, is largely based on the standard conservation narrative with its roots in (non-scientific) natural history and the ‘back-to-nature’ movement. It’s crucial, however, that regulation is seen to have the imprimatur of science, which means that science is managed to produce results that support the imposition of ever greater regulation. This is why studies like mine (and your dormouse example) are so threatening – they undermine the rationale of established conservation policy, and the status and income of those responsible for, and dependent on such policy. The unfortunate side effect of this is that scientific enquiry is stifled, and conservation itself is compromised, since only science can produce real solutions.



Sorry to break this to you, but it’s the other way round. JDSS was one of the first people I send the paper to when it was in press, and he sent back a critical reply with the caveat that ‘I hope we can disagree and still be friends’. Encouraged by this, I responded to his criticisms and we exchanged a series of mails, during which he gradually became more tetchy, and ultimately cut off the correspondence. I would be happy to publish this, but he has refused to approve it, so I won’t. His unwillingness to debate the issues has not prevented him from repeatedly reviewing my work in a hostile manner – on one occasion the editor of British Birds agreed to disregard one of his reviews since it was so obviously biased. JDSS also refused to release the review he wrote for the first submission to the Independent competition.

On the whole his interventions in the sparrow debate have not been very well judged or enlightening – witness the interventions by Klaus Witt and Crick & Robinson in British Birds (89:146, & 96:306-7). The obsession with diesel and MTBE may be more of a penance for a lucrative career in the petrochemical industry than anything else.

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

 

[Jane Turner]

he would answer Jane Turner but doubts that she'd understand.

I had a good old belly laugh at that too...that and the subtext comment about correlations.


Remind me, who has actually been employed as a research scientist

 

[Jane Turner]

Another tempo-spatial data set available here

 

[Jane Turner]

The only thing I never respond to is Alf Arbuthnot, because following our lengthy exchange in March/April, it became all too apparent that (i) he is grossly abusive (ii) his responses rapidly degenerate into meaningless babble. You, on the other hand are merely snarky and evasive, which is why there is potential (at the margin) for meaningful debate (which you always lose). So what is it exactly about my methodology, sample sizes and designation of site type that you have a problem with?

So let's give it a try...

- How many results are included in in each zone/site type classification? (and what is the probability of misclassification)

- How precisely did you determine the classification with each site?

- Which are the results you excluded in terms of zone and type.

 

[DMW]

It’s a shame this thread has largely descended into a pi**ing match, since the underlying subject matter is very interesting.

I live on Jersey. Sparrowhawks became extinct as a breeding species in the 1950s, and for the next few decades were essentially a vagrant – I might see 1-2 per year in the early 1980s. During this period of local extinction, House Sparrow populations declined markedly.

In the last decade or so, Sparrowhawks have firmly re-established themselves as a breeding species, and are probably at carrying capacity. For the last 3-4 years, House Sparrow numbers do seem to be on the rise.

If I was a mischievous sort, I might suggest that there may be a causal link in this positive correlation!

For the sake of balance, I should also say that Cirl Buntings, Reed Buntings, Yellowhammers and Stonechats all died-out (or virtually so) as breeding species during the last decade, and I am open-minded about the possibility that Sparrowhawks were at least partly responsible.

 

[Nightranger]

I live on Jersey. Sparrowhawks became extinct as a breeding species in the 1950s, and for the next few decades were essentially a vagrant – I might see 1-2 per year in the early 1980s. During this period of local extinction, House Sparrow populations declined markedly.

In the last decade or so, Sparrowhawks have firmly re-established themselves as a breeding species, and are probably at carrying capacity. For the last 3-4 years, House Sparrow numbers do seem to be on the rise.

If I was a mischievous sort, I might suggest that there may be a causal link in this positive correlation!

For the sake of balance, I should also say that Cirl Buntings, Reed Buntings, Yellowhammers and Stonechats all died-out (or virtually so) as breeding species during the last decade, and I am open-minded about the possibility that Sparrowhawks were at least partly responsible.

I know Jersey quite well for various reasons, DMW and I know there were big issues of habitat degradation. Indeed, some of the factors may well have led to the decline of the sparrowhawk too when you think about it. I have seen Jersey's Biodiversity Action Plan and what is so lovely about it is that a lot of it is in place now and things are improving. This is even more remarkable on a small island with more than 100,000 people. Sadly, this came all too late for cirl buntings, reed buntings, yellowhammers and stonechats (all of which have declined over much of their natural range anyway) but it has paid dividends for the Dartford warbler even allowing for the odd fire on the heathland. Having said that, I doubt if anyone could say for certain that sparrowhawks were not capable of finishing off an already limited population but that also applies to cats and feral ferrets.

Note on edit: There is some evidence from various sources that predators can further exascerbate an already dire situation but this is not necessarily the same as saying they were responsible for the initial turn towards decline. Visual predators such as the sparrowhawk could (even in theory) pick the more unusual members out of a community, as happened with an American robin on Humberside (?) a few years back. However, it is not difficult to see that this essentially means a species so rare that it was probably destined for local/national extinction anyway due to there being a too small gene pool.

 

[Nightranger]

Further to the BTO’s disinformation leaflet on sparrows, I’ve just picked up this little gem from their ‘Birdtrends’ page:

“Negative correlations between indices of Sparrowhawk presence during its recolonisation of the UK and House Sparrow abundance from the Garden Bird Feeding Survey have been interpreted as evidence that increasing predation rates are depressing House Sparrow populations (Bell et al. 2010). However, more sophisticated analyses of large-scale and extensive national monitoring data provide no evidence that House Sparrow population declines were linked to increases in Sparrowhawks (Newson et al. 2010).”

Note the subtext of ‘it’s just a correlation’ in their description of my paper, and the ludicrous description of Newson’s awful paper as ‘more sophisticated’. What they’re saying to Joe Public is ‘don’t worry, this is all above your heads but we know best, so keep on trusting us (and handing over the money)’. The rest of the entry is nothing more than textbook exercise in spin, and it can’t help but raise the question as to whether we can really trust anything this partisan and politically-driven organisation says about birds.

I have mentioned this before Dr Bell, but it amazes me that a grown man can resort to such childish language. The quote you have pulled out merely gives a critical response to your work and I do not see anything in there that is deserving of your silliness in response. It is just you who is taking umbrage to a percieved insult that in reality does not exist. Just because there is a claim that more sophisticated methods were used for the BTO paper does not suggest your methods were faulty. In fact, the BTO are doing what I would expect any scientific organisation to do and actually acknowledging your work, which they do not have to do under the circumstances. Your attitude on here, on your own website and on YouTube has been a darn sight more disrespectful.

PCA and other multivariate techniques are the friend of the pseudoscientist. The data rarely conform to the statistical assumptions of the technique (and certainly don’t in this case), so can appear to throw up all kinds of random relationships, one of which might be just what you’re looking for. If not, you can just leave it out and no-one is the wiser. Even assuming the PCA axis used expresses some meaningful environmental gradient connecting 100% concrete at one end with 100% deciduous shrubs at the other, there will be so many covariates that it is impossible to draw any meaningful inference from a relationship with sparrow breeding success.

No Dr Bell, why is taking a multi-variate approach any less valid than starting with an assumption and trying to work a model round it? I will keep repeating this but your model is the equivalent of the two-body theory in physics - it cannot work and it does not work in a real-world situation. As you will know, no one has solved the three-body problem and there is a suspicion that no one ever will. Biology is always about multi-variates even if you accept or propose there is one important causative to a population trend (up or down). The more you ignore other factors, the more your data will swing away from a real-world representation. Unfortunately, I think you already know that even if you test your model with other variables, it will quickly depart from what you want it to tell you.

One thing that strikes me with a mono-variate approach is what kind of data spread do you get? If you plotted this, would it produce a bell-diagram (pun not intended)? I cannot imagine a plot where every data point coincides and this means there must be large tails at either end. On one hand, you have negative correlation between sparrowhawks and sparrow decline and at the other end approaching certainty that sparrowhawks are causing sparrow declines. Indeed, the extremes of the model should theoretically produce tails that say sparrows will prosper with the presence of sparrowhawks and sparrowhawks have rendered sparrows extinct. Obviously, I would not expect data at these points but I am wondering how you produce a model that skews the peak into the significant effect side anyway. What is more, you seem to be telling everyone the model skews the peak into the critical effect area of the plot and I am not sure how you can get that with a predator-prey model unless you artificially raise the predator population too high (certainly higher than it would be in the real-world). To do this, either produces cyclic crashes of both predator and prey that only just recovers short of extinction of both or tip it too far and it is mutual extinction. I certainly do not see anything cyclic in population data so far and the decline of house sparrows has decelerated as it reaches a lower level. Sparrowhawks are declining at a non-significant rate that is completely out of step with house sparrows.

Sorry to break this to you, but it’s the other way round. JDSS was one of the first people I send the paper to when it was in press, and he sent back a critical reply with the caveat that ‘I hope we can disagree and still be friends’. Encouraged by this, I responded to his criticisms and we exchanged a series of mails, during which he gradually became more tetchy, and ultimately cut off the correspondence. I would be happy to publish this, but he has refused to approve it, so I won’t. His unwillingness to debate the issues has not prevented him from repeatedly reviewing my work in a hostile manner – on one occasion the editor of British Birds agreed to disregard one of his reviews since it was so obviously biased. JDSS also refused to release the review he wrote for the first submission to the Independent competition.

Why be sorry? You say nothing of your own attitude during these exchanges with JDSS but given your willingness to dismiss anything that counteracts your own work, I can only imagine that it was not pleasant. Sadly, I have never had the fortune to meet JDSS but I have found him more than helpful during email exchanges and I understand from personal testimonies that he is a very quiet man face-to-face. Interesting that you should point to what you perceive as a mistake by JDSS but you are completely unwilling to accept that you are even capable of making mistakes.

On the whole his interventions in the sparrow debate have not been very well judged or enlightening – witness the interventions by Klaus Witt and Crick & Robinson in British Birds (89:146, & 96:306-7). The obsession with diesel and MTBE may be more of a penance for a lucrative career in the petrochemical industry than anything else.

This is sad in the extreme Dr Bell so I am going to ask you a question here. Do you or have you ever kept cagebirds, racing pigeons or go/gone gamebird shooting? If not, do you know someone who does/has? This is essentially a rhetorical question because I am sure you will anticipate where I am going with this. However, if you want to make a childish dig at someone else, as in the above paragraph then I think it is only fair that you declare your own background.

 

[AlfArbuthnot]

However, if you want to make a childish dig at someone else, as in the above paragraph then I think it is only fair that you declare your own background.

His own background, which is highly revealing with regard to his attitude to mainstream scientists and institutions, is neatly encapsulated within this article:

http://www.thecnj.com/camden/2009/043009/news043009_04.html

Bluechaffinch, please note that this link is being used once again as evidence which perhaps explains the underlying reasons why CPBell may have an axe to grind against 'the establishment' and all its minions.

 

[Nightranger]

His own background, which is highly revealing with regard to his attitude to mainstream scientists and institutions, is neatly encapsulated within this article:

http://www.thecnj.com/camden/2009/043009/news043009_04.html

Bluechaffinch, please note that this link is being used once again as evidence which perhaps explains the underlying reasons why CPBell may have an axe to grind against 'the establishment' and all its minions.

Thanks Alf, I would still like to know where the single-minded attitude against sparrowhawks comes from though.

 

[DMW]

Nightranger, thanks for the comments. I agree it’s unlikely that Sparrowhawks alone were responsible (if at all) for the local extinctions of the species I mentioned, but as you effectively note, it’s not impossible that they were the final straw, as it were.

Small insular populations are perhaps always more vulnerable to random events, and certainly the Yellowhammer population was always very small (in my lifetime at least).

The declines of Cirl Bunting and Stonechat were more puzzling – the populations of both were seemingly stable into the 1990s, then crashed and all but disappeared over the course of a few years in the mid-1990s.

More positively, Dartford Warblers are indeed thriving here, although I think it’s perhaps more to do with milder winters than active habitat management. And of course, the Sprawks can’t get the little blighters when they bury themselves in gorse bushes

 

[Nightranger]

The declines of Cirl Bunting and Stonechat were more puzzling – the populations of both were seemingly stable into the 1990s, then crashed and all but disappeared over the course of a few years in the mid-1990s.

As I said DMW, these species are not prospering over the whole of the range and this is suspected to be a key ingredient when considering some local declines/extinctions. The funny thing about this effect is that population sinks may be operating and they can be difficult to detect until the situation has progressed to a very serious level. Essentially, it is like objects being drawn into the plughole of a sink when the plug is removed except it is often caused by habitat preference of a species. What happens is that a species can be drawn into continuing to breed in its core habitat even though there is a factor that is reducing breeding success to a critical level. This has the effect of drawing the species in from the periphery of its range yet numbers are not replaced within the core. This can go on for many years until there are no longer enough individuals to draw into the core. It may even have happened with the house sparrow although with a largely sedentary lifestyle, the contraction seems to have happened quite quickly to produce isolated colonies. Unfortunately, the worst effects are going to be noticed in migratory and nomadic species that can and do move away from peripheral or non-prefered (not the best way of putting that) breeding sites.

 

[Wildmoreway]

The present apparent increase in the numbers of house sparrows could simply be down to them having now evolved to be able to better exploit the changed environment. This has happened with other species in the past such as the peppered moth.

 

[Nightranger]

Incidentally, this is one version of the predator - prey game that I mentioned further down the thread. Dr Bell will deny it but this is effectively what his model is built upon.

http://www.leinweb.com/snackbar/wator/