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

[AlfArbuthnot]

Secondly, the posts 'against' Dr Bell have been based entirely on the context that 'no, you are wrong, it's not sparrowhawks but a range of other anthropogenic reasons such as building design, changes to 'good old' farming practices etc etc'. .

This is wrong. Several posters have been trying to get CPBell to discuss his methods in detail, but he has flatly refused. He is simply not interested in exploring the methods of his work in detail, he just wishes to discuss the conclusions. He appears to want to avoid the situation of flaws being highlighted in his methods, which will therefore undermine the conclusions that he is clinging to. All we are getting from him here is repeated assertions of faith ("I believe..."), very harsh attacks on anyone who disagrees with him or who don't want anything to do with him (such as RSPB and BTO), and a refusal to discuss the details of the methods that he thinks are a revolution in science. This isn't a grilling or a debate, it's a constant stream of position statements. And as long as CPBell thinks it necessary to make unsubstantiated leaps of faith and attack people with a far more impressive scientific track record than his own (which is essentially blank), then others will probably wish to highlight his errors, inconsistencies and flawed logic that are swept along in the torrent of obvious, angry, bitterness (see his last post).

 

[Jos Stratford]

...Dr Bell's thesis, it is surely to be welcomed that posters on this forum have had the rare, if not unique, opportunity to really grill the author of a paper about the fine details of their research ...

There has been no opportunity to grill the author. Bell does not answer questions regarding methodology, just spews the same conspiracy theories time after time.

 

[Amarillo]

The author has certainly been grilled, but its all a bit pointless since he doesn't answer the questions and continues with his agenda against the RSPB/BTO

This thread goes round and round in circles and Bell ensures that it keeps going because without it, all interest in his work is gone. The publicity his paper has received due to this epic thread seems way out of proportion to the relevance of his work and I think a more general thread about sparrow decline would be more interesting - note the more interesting direction the thread takes whenever Bell is not involved.

 

[London Birder]

... I think a more general thread about sparrow decline would be more interesting - ...

here, here.

 

[Jane Turner]

Secondly, the posts 'against' Dr Bell have been based entirely on the context that 'no, you are wrong, it's not sparrowhawks but a range of other anthropogenic reasons such as building design, changes to 'good old' farming practices etc etc'. ..

Er pardon???

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....

Ah I see I am not the first to point this out.

 

[Nightranger]

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???

...or could the increase be helped by better education and the fact that a lot of people now put up sparrow nest boxes in preference to blue tit boxes?

 

[AlfArbuthnot]

The author has certainly been grilled,

And eventually toasted?

 

[Nightranger]

Salt eh? Well I never..

Apart from this being a rather childish response from a grown man, why should this idea be so alien to you? I assume that you know that most birds cannot deal with high salt content in their diet and that is why there has been advice to take care when putting out kitchen scraps. However, it makes good sense to consider that this may have been a problem in larger urban areas where sparrows would have been feeding on fast food detritus containing a high salt content. I don't know of any research on the subject but that is no reason to dismiss the idea out of hand

I’ve had the pleasure of reading the BTO’s latest House Sparrow offering in the form of a “factsheet”, which I’ll attach to this post. It’s not available for download - you have to request it so they can get your details for their marketing database.

I hope you checked the conditions for redistribution. As for the last bit of this paragraph, so what! Just about everyone is doing this these days and under DPA you can request that you are not contacted further and that your details are not passed on to a third party.

So as not to frighten the horses (or is it the RSPB?) they quickly qualify this with a genuflection to Peach’s dodgy PCA analysis in his Animal Conservation paper showing a marginal relationship between shrubbery and breeding success.

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.

They also recite the usual RSPB-approved liturgy about loss of stubbles and spilled grain in the countryside (forgetting their own research which indicates to the contrary), and off-road parking spaces and plastic fascia boards in the cities. They then go on to recommend you let your lawn go to pot (nice for the neighbourhood – haven’t they heard of the broken-windows theory?) and put up ‘terrace’ nestboxes (which don’t work).

Hang on, hang on! You are back to providing critiques on rural house sparrow research whereas your work only related to urban house sparrows, right? I realise you never answer all the points that are put to you but I have already pointed at the flawed logic in applying causes for decline in urban sparrows to rural sparrows and vice versa. BTW, terraces do work albeit that they are not as efficient as was hoped and if you look hard enough there is plenty of advice to put up spaced individual sparrow boxes. I know because that is what I have been telling people to do for years. The terraces will attract sparrows but often in only one of the chambers (with other chambers being occupied by blue tits and great tits but rarely, other sparrows). All this goes to prove is that house sparrows are not as tolerant of each other and there must be a discreet spacing tolerance during nesting unlike with tree sparrows.

 

[AlfArbuthnot]

whereas your work only related to urban house sparrows, right?

No, he classified gardens as rural and urban. But he wont tell us how exactly, so we can't tell if it's a meaningful distinction. But from what titbits he's given away, it seems to be a source of significant potential error in his study, which is probably why he has refused to discuss it further (I sense that the mindset is that fallibility is something that only occurs in others).

 

[bluechaffinch]

Er pardon???

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....

Ah I see I am not the first to point this out.

There are possibly a maximum of three regular contributors to this thread who have taken Dr Bell to task over the nuances of methodology and who are probably capable of doing so. The overwhelming majority of posts, stretching to over 1300 now, do no such thing - I have taken the trouble to look through the whole debate before you ask. If you too look back you will see that there is a great deal of explanation about methods from Dr Bell - the issue is whether these are valid or not and this issue seems to be a running sore. I hope you get the answer you are looking for.

As I said it is a very rare event indeed for the author of a paper (whatever you or anyone else thinks of it) to be available for such a grilling, regardless of whether you believe he has not answered your queries or not. Fair play I say. I wonder whether if we replaced the word 'sparrowhawk' with 'cat' people would be getting their knickers in such a twist...

What I object to from the 'anti'- side (my term, probably a better one somewhere...) is that (amongst other things) on the one hand Dr Bell is vilified for being aggressive etc but then folk are more than happy to drag out, for example, stories of long-past employment tribunals as apparent evidence that he is a thoroughly untrustworthy character (this happened very early on in the thread, whilst Dr Bell was being very open in my opinion). He may be abrasive, but this does not mean he is wrong. You may disagree with him but again this does not mean he is wrong. This thread is a bit like a school playground squabble at times.

As I have no competence in detailed statistical methodologies (again, very few here have I suspect) I have not been able to involve myself in this side of the debate, however if the crux of the issue appears to be his method of allocating broad habitat types then for goodness' sake how on Earth does anyone think this is done for most papers? Do you think that lead authors visit every site and rigorously check the habitat composition of each study site? I don't think so. For example, as a bird ringer, the habitat codes I use for ringing sites are really rather broad-scale yet are used to make assessments subsequently used in all sorts of studies by the BTO and others. I have been involved in enough ornithological surveys myself to know that the donkey work is left to students/volunteers who if they are lucky get a crib sheet and a quick toolbox talk. Please let us not believe that everyone else's methods apart from Dr Bell's are 100% beyond reproach.

Carry on...

 

[Jane Turner]

= I wonder whether if we replaced the word 'sparrowhawk' with 'cat' people would be getting their knickers in such a twist....

Scientifically... if the robustness of the methodology suggesting cats were correlated was as secure as Dr Bells, and then the results were used to make such sweeping statements, then the criticism would be identical

 

[London Birder]

Scientifically... if the robustness of the methodology suggesting cats were correlated was as secure as Dr Bells, and then the results were used to make such sweeping statements, then the criticism would be identical

... he may get a three minute slot on The One Show.

 

[MJB]

Beyond the UK setting, I am not sure the overflow idea holds true - at least here in eastern Europe, Starlings are abundant and, whilst present in urban areas, the higher densities are certainly in semi-rural and rural areas, nesting commonly in farmsteads and rural gardens, as well as completely natural locations.

Things may have changed since the 1990s, but my understanding is that the productivity of core populations was pretty much always enough to ensure that the surplus was 'exported' so that the fringe populations' lower productivity was supplemented. For as long as there were functioning livestock industries towards the breeding range limits, Starling numbers could be maintained by this mechanism, because livestock cropped grass and disturbed much of the surface, allowing Starlings to take advantage of exposed prey. Once livestock were concentrated year-round in huge sheds (commonplace in Europe), the amount of food for the birds diminished, and so fewer survived the winter. The 'exported' surplus was insufficient to maintain populations near the range limits, and so the breeding range contracted towards the core populations.
MJB

 

[AlfArbuthnot]

If you too look back you will see that there is a great deal of explanation about methods from Dr Bell - the issue is whether these are valid or not and this issue seems to be a running sore.

No, several people have asked for (1) sample sizes, (2) the method of map classification, and (3) how many misclassifications it would take to make the effect disappear. He has not given answers to any of those crucial questions. It has also been asked why Sparrows would decline when other garden species classed as 'vulnerable' in scientific studies (Greenfinch, Chaffinch) have increased. No attempt at answering this has been given, which undermines the entire hypothesis.

As I said it is a very rare event indeed for the author of a paper (whatever you or anyone else thinks of it) to be available for such a grilling,

But the above shows that the author is not available for a grilling. The author instead appears to be available only for repeating claims about the conclusions, and the work of other people.

What I object to from the 'anti'- side (my term, probably a better one somewhere...) is that (amongst other things) on the one hand Dr Bell is vilified for being aggressive etc but then folk are more than happy to drag out, for example, stories of long-past employment tribunals as apparent evidence that he is a thoroughly untrustworthy character (this happened very early on in the thread, whilst Dr Bell was being very open in my opinion). He may be abrasive, but this does not mean he is wrong.

I can understand this opinion, and it is not pleasant. In short, personal attacks were made against others, which made it pertinent to discuss the possible reasons, which may have been related to public behaviour (everything discussed about CPBell has been in the public domain, some of it put online by himself).

You may disagree with him but again this does not mean he is wrong.

I agree entirely. But CPBell is telling us that he is RIGHT. And we are simply asking him to prove it, by answering the further questions that are being posed. I, and perhaps others, are not saying that CPBell is wrong, but simply that his evidence is not strong enough to be conclusive. He does not accept this.

however if the crux of the issue appears to be his method of allocating broad habitat types then for goodness' sake how on Earth does anyone think this is done for most papers?

They will use a quantitative method (i.e they will count things). Whereas as far as CPBell has given away, he used a qualitative method (i.e. his students made a rough guess of the number without counting). That is quite a serious source of error.

Also, you will find very few papers where the author suggests that their answer is the last word on a subject, and the case is now closed. In fact, CPBell's paper does not make this claim either. But on this thread, he IS stretching his conclusions and appears to making a claim of certainty. This is the second major bone of contention for me.

Do you think that lead authors visit every site and rigorously check the habitat composition of each study site? I don't think so.

I would expect that if someone is claiming that an area of a map is more or less than 50% of something, then they will have measured that on the map (which is very easy), and not simply looked at it and guessed (which is what seems to have happened). This is because a 'by eye' estimate is likely to find it difficult to tell 45% from 55%, yet in CPBell's method this difference was critical.

 

[AlfArbuthnot]

For as long as there were functioning livestock industries towards the breeding range limits, Starling numbers could be maintained by this mechanism, because livestock cropped grass and disturbed much of the surface, allowing Starlings to take advantage of exposed prey. Once livestock were concentrated year-round in huge sheds (commonplace in Europe), the amount of food for the birds diminished, and so fewer survived the winter. The 'exported' surplus was insufficient to maintain populations near the range limits, and so the breeding range contracted towards the core populations.
MJB

In addition, the vet drugs given to cattle mean that cowpats support far fewer invertebrates these days. And grassland now tends to be 'improved' (i.e. fertilised), which reduces plants diversity and so probably insect abundance/diversity.

There was also a huge shift from sheep to arable cash crops (e.g. rape) from the early 1980s, so massively reducing the area of short grassland. These newly-arable fields were then sprayed with insecticide and slug pellets, wiping out most of the invertebrates that were left.

 

[MJB]

In addition, the vet drugs given to cattle mean that cowpats support far fewer invertebrates these days. And grassland now tends to be 'improved' (i.e. fertilised), which reduces plants diversity and so probably insect abundance/diversity.

There was also a huge shift from sheep to arable cash crops (e.g. rape) from the early 1980s, so massively reducing the area of short grassland. These newly-arable fields were then sprayed with insecticide and slug pellets, wiping out most of the invertebrates that were left.

Thanks Alf, for the added info.
MJB
PS You don't 'alf type quickly!

 

[Wildmoreway]

An interesting thread here

http://www.wildaboutbritain.co.uk/f...-and-rise-house-sparrows-petrol-involved.html

and here

http://www.telegraph.co.uk/earth/ea...rs-falling-because-of-decline-in-gardens.html

 

[Jane Turner]

With 20 responses it has more points as some of Dr Bell's sets... as far as it has been possible to tell.

 

[bluechaffinch]

I can understand this opinion, and it is not pleasant. In short, personal attacks were made against others, which made it pertinent to discuss the possible reasons, which may have been related to public behaviour (everything discussed about CPBell has been in the public domain, some of it put online by himself).

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...

They will use a quantitative method (i.e they will count things). Whereas as far as CPBell has given away, he used a qualitative method (i.e. his students made a rough guess of the number without counting). That is quite a serious source of error.

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.

Also, you will find very few papers where the author suggests that their answer is the last word on a subject, and the case is now closed. In fact, CPBell's paper does not make this claim either. But on this thread, he IS stretching his conclusions and appears to making a claim of certainty. This is the second major bone of contention for me.

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.

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'. An example, in my line of work I deal with numerous local planning authorities. 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.


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.

As you were...

 

[Allen S. Moore]

Nevertheless the first recommendation offered is to provide thick cover so that sparrows can ‘escape from predators, rest, roost and socialize’ (for which read ‘escape from predators’ – otherwise why not rest, roost and socialize out in the open?).
[/URL]

lest we let dismissive assumptions get in the way of the facts, there are some numbers for you here http://www.bbc.co.uk/news/uk-18623096

I was listening to several house sparrows chirping away in my little garden this evening, but when I looked out it was difficult to see them in the dense bush, unintentionally putting the first recommendation in practice. Reading the BBC link reminded me that some gardens are just too tidy for birds, but mine isn't!

I have spent a lot of holidays in Catalunya in NE Spain, and note how numerous house sparrows are there, and they have sparrowhawks, too. Indeed, when I was there last month I stayed in the coastal town of L'Ampolla and spent 30 minutes at dusk one evening making a rough count of the house sparrows flying north over or past the balcony of my room, arriving at a figure of 750. Fantastic Life, eh? There were no sparrowhawks about, but a hobby made 3 swoops at the sparrows. Aren't hobbies increasing over there in Britain? Just joking, of course.

Reading some of the justifications of the results of scientific research that sparked this long thread I couldn't help being reminded of a lecture that I once attended at work. It was about the tobacco industry's attempts to distance its products from the observed effects of passive smoking. One bit of their "scientific" research correlated the effects with drinking green tea. I would claim to be scientific myself, but it seems that figures can often be presented to support any answer, correct or not, for whatever the non-scientific reasons for distortion are.

Allen