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  • All quiet on the sparrow front

    House Sparrows are soooo last decade, but anyone still interested in why they disappeared might want to take a look at an article just published in the journal International Studies on Sparrows.

    Alternatively, they could just take a look at THIS.

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

  • #2
    Explain http://blx1.bto.org/gbw-dailyresults...bwr471-20.html - c.f http://www.flickr.com/photos/barryboswell/6240575196/

    Comment


    • #3
      Was that a joke?

      Oh dear - if only it were that simple. I would expect something that kind of analysis from school children. They are 'Sparrow'hawks so it must be their fault - tosh!

      Comment


      • #4
        Originally posted by part time birder View Post
        Oh dear - if only it were that simple. I would expect something that kind of analysis from school children. They are 'Sparrow'hawks so it must be their fault - tosh!
        You sound like you've read the paper carefully. What specifically about it do you object to?

        If you take a look at this, you'll see that the Goldfinch has the signature population crash coinciding with Sparrowhawks reinvading lowland England in the mid-1970s, and that before that the species was increasing rapidly. Several other species similarly affected have also started to recover since, such as Song Thrush and Blackbird - there is no reason why a species affected by predation cannot begin to recover following a change in its behaviour, such increased predator aversion or exploitation of new food resources.

        I should also remind you that I'm not asserting that any species apart from the House Sparrow have been affected by Sparrowhawks. This is because I haven't been able to do the relevant analyses thanks to the non-cooperation of the RSPB and the BTO.

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

        Comment


        • #5
          Originally posted by cpbell View Post
          House Sparrows are soooo last decade, but anyone still interested in why they disappeared might want to take a look at an article just published in the journal International Studies on Sparrows.

          Alternatively, they could just take a look at THIS.

          http://www.cpbell.co.uk
          http://www.youtube.com/CultoftheAmateur
          I'm sure we're all tired of this story by now, but here's some support for the theory based on independent research:

          Response to Predation Risk in Urban and Rural House Sparrows
          Gábor Seress, Veronika Bókony, János Heszberger, András Liker

          Habitat urbanization may change the density of predators, and it is often assumed that such changes lead to altered predation risk for urban populations of their prey. Although it is difficult to study predation hazard directly, behavior responses of prey species may be informative in inferring such habitat differences. In this study, we compared the risk-taking behavior of urban and rural house sparrows (Passer domesticus) after simulated attacks by two of their important predators (sparrowhawk Accipiter nisus and domestic cat Felis catus). The birds were startled by moving dummies of these predators and respective control objects, and their risk taking was estimated as their latency to feed after the startle. We found that sparrows responded more strongly (had longer post-startle feeding latencies) to sparrowhawk attacks than to the control object, and their responses differed between the habitats. First, risk taking of urban birds strongly decreased with age (older birds had longer latencies than young birds), while there was no such age difference in rural birds. Second, young urban birds responded less strongly, while older urban birds responded more strongly to the sparrowhawk than the same age groups of rural birds, respectively. We did not succeed in evoking antipredatory response by simulated cat attacks, because birds responded similarly to the dummy and the control object. Our results support that predation risk, posed at least by avian predators, is different in urban and rural habitats of house sparrows. The increased wariness of older, hence presumably more experienced, urban birds implies that sparrows may be more exposed to predation in cities.


          http://onlinelibrary.wiley.com/doi/1...1.01944.x/full

          from that paper:

          The reduced risk taking of urban sparrows after the attack by aerial predators such as the sparrowhawk is consistent with several observations indicating increased raptor densities in cities. The sparrowhawk is a main predator of the house sparrow, and its numbers are increasing in several urbanized habitats (Chamberlain et al. 2009b; Bell et al. 2010), reaching high densities in large European cities like Hamburg (Risch et al. 1996) or Prague (Kelcey & Rheinwald 2005). In Budapest (where two of our urban capture sites were located), breeding sparrowhawks are present from the early 1980s (Bagyura 1985); since then, their population has been increasing, and in 2007, the number of breeding pairs was estimated to 200 (Be´rces 2007), which exceeds the breeding density of sparrowhawks in many natural habitats (Newton 1986). Furthermore, the number of sparrowhawks hunting in Budapest during winters is estimated to reach 500–600 individuals (Z. Bajor, pers. comm.). Other raptors such as the kestrel (Falco tinnunculus), the merlin (Falco columbarius), and the northern goshawk (Accipiter gentilis) also readily occupy metropolitan areas in both Europe and North America (Sodhi & Oliphant 1992; Salvati et al. 1999; Morandini 2006; Rutz 2006).

          I don't really see this as some sort of conservation problem. We have a natural world out of equilibrium; the rebounding Sparrowhawk population may may have been a significant driver of population declines - along with a host of other factors. We would expect populations to become more Sparrowhawk-savy and begin to bounce-back.

          I don't see the Sparrowhawk argument as being anything the Songbird Survival group could 'use against' raptors. What we need is better protection of raptors, that way we get back species like Goshawks - the intra-guild predators that naturally regulate populations of Sparrowhawks, Magpies, Crows and assorted other meso-predators. The results of the recent papers showing the extent of persecution of these species are shameful to behold. Sure they will eat people's Pheasants (and Honey Buzzards) but ultimately a balance will be reached...
          Dept. of Zoology, University of Cambridge, UK

          My website - Neotropical Bird Club -Tropical Forest Research - Punkbirder - Wikiaves

          In natural science the principles of truth ought to be confirmed by observation. — Carolus Linnaeus

          Comment


          • #6
            Originally posted by Alex Lees View Post
            I'm sure we're all tired of this story by now, but here's some support for the theory based on independent research:

            Response to Predation Risk in Urban and Rural House Sparrows
            Gábor Seress, Veronika Bókony, János Heszberger, András Liker
            Thanks for pointing this out. It supports my conjecture in the original Auk paper that urban sparrows were picked off because they had lost predator aversion. Urban juveniles showed the lowest latency, indicating a low level of inherited predator aversion, while urban adults showed the highest latency, indicating a high level of learned predator aversion. Rural adults and juveniles showed intermediate latency, indicating inherted behaviour in line with environmental conditions.

            Do I gather that you agree that mesopredator release is a significant factor in the declines of small birds in Europe and other heavily farmed landscapes? If so, would you agree that the RSPB led line that raptors etc. are totally innocent is a problem for conservation? Would it not be better to do the research needed on predation effects, then have a rational debate about the way forward, instead of wasting resources on ineffective BAPs and agri-schemes? What’s more important – effective conservation or saving Will Peach’s blushes?

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

            Comment


            • #7
              Originally posted by cpbell View Post
              Do I gather that you agree that mesopredator release is a significant factor in the declines of small birds in Europe and other heavily farmed landscapes?
              Meso-predator release is a significant factor driving population declines globally. Where I did my PhD fieldwork it was armadillos, opossums and small primates polishing off all the nests of birds in small forest patches devoid of large cats and forest eagles. It acts synergistically with other factors, for instance we get this ridiculous vicious cycle in the UK:

              1) Landowners release tens of millions of Pheasants into the countryside.

              2) Gamekeepers charged with protecting them kill top predators like Goshawks which take some pheasants (despite this palling into comparison with natural mortality).

              3) Populations of meso-predators increase as they are released from control, gamekeepers hammer the meso-predators too as these also impact upon Pheasant numbers (by eating any next generation Pheasants).

              4) Conservation organisations complain that gamekeepers are killing everything, environmental legislation kicks in and meso-predators get a chance (as do top predators but they are more k-selected and take longer to recover), indeed their populations are massively boosted by the gamekeepers subsidised feeding of them (by the tens of thousands of roadkill Pheasants).

              5) Meso-predators increase, songbirds decrease and the landowners blame all raptors for driving down populations of the pretty songbirds. We all know this is a front for more nefarious reasons. This all happens in parallel with landscape-wide changes in the farmland environment.

              Your paper inadvertently (?) acts as a rallying call for the likes of those that would set a cull. It needn't do, if we view the situation holistically.

              Originally posted by cpbell View Post
              If so, would you agree that the RSPB led line that raptors etc. are totally innocent is a problem for conservation? Would it not be better to do the research needed on predation effects, then have a rational debate about the way forward, instead of wasting resources on ineffective BAPs and agri-schemes?
              Maybe the RSPB takes too strong a line, but then debates are polarising. You've done the same by apportioning all the blame on raptors and claiming that existing agri-environment schemes are useless. That is nonsensical. Improving habitat quality must be beneficial for wildlife. Think about it.
              Originally posted by cpbell View Post
              What’s more important – effective conservation or saving Will Peach’s blushes?
              You'd come over much better if you were less combative/paranoid...

              Ps. here’s a good line of research for you, out here in Amazonia, I have multiple lines of anecdotal evidence that populations of House Sparrows have crashed across the board, certainly they are rare in Belém – still need it for my window list. Maybe this is the typical response of a recent introduction (they’ve been here for just 80 years) – classic boom/bust trajectory, but maybe its symptomatic of the ‘clean city’ hypothesis. To be fair Belém is still dirty as sh*t but there aren’t many horse-drawn carts anymore and no grain spillage in the city. No raptors either – just the odd Roadside Hawk and Bat Falcon, certainly no Accipiters anywhere near the city and other similar-sized passerines such as Palm Tanagers are mega common. I could probably tee-up an MSc student to work on the question....
              Dept. of Zoology, University of Cambridge, UK

              My website - Neotropical Bird Club -Tropical Forest Research - Punkbirder - Wikiaves

              In natural science the principles of truth ought to be confirmed by observation. — Carolus Linnaeus

              Comment


              • #8
                Originally posted by Alex Lees View Post
                Meso-predator release is a significant factor driving population declines globally. Where I did my PhD fieldwork it was armadillos, opossums and small primates polishing off all the nests of birds in small forest patches devoid of large cats and forest eagles. It acts synergistically with other factors, for instance we get this ridiculous vicious cycle in the UK:
                Sensible comments for the most part, and just the kind of debate that is needed.

                Originally posted by Alex Lees View Post
                Maybe the RSPB takes too strong a line, but then debates are polarising. You've done the same by apportioning all the blame on raptors and claiming that existing agri-environment schemes are useless. That is nonsensical. Improving habitat quality must be beneficial for wildlife. Think about it.


                You'd come over much better if you were less combative/paranoid...
                I’m often accused of being strident, but remember that the argument is me on one side and a mega-corp with a £100 million annual turnover on the other, and only a fool sticks to Queensberry rules while the other guy is kicking him in the nuts. So far as agri-environment schemes are concerned, I’m only quoting the bare facts concerning the Farmland Bird Indicator. The schemes are specifically designed to help this recover but it hasn’t happened, and the excuses get thinner every year that goes by.

                Originally posted by Alex Lees View Post

                Ps. here’s a good line of research for you, out here in Amazonia, I have multiple lines of anecdotal evidence that populations of House Sparrows have crashed across the board, certainly they are rare in Belém – still need it for my window list. Maybe this is the typical response of a recent introduction (they’ve been here for just 80 years) – classic boom/bust trajectory, but maybe its symptomatic of the ‘clean city’ hypothesis. To be fair Belém is still dirty as sh*t but there aren’t many horse-drawn carts anymore and no grain spillage in the city. No raptors either – just the odd Roadside Hawk and Bat Falcon, certainly no Accipiters anywhere near the city and other similar-sized passerines such as Palm Tanagers are mega common. I could probably tee-up an MSc student to work on the question....
                DaSilva & Oren (1990) say that the 1920s introduction to Belem died out quickly, and that they were re-introduced from Rio de Janiero in 1978, increasing to 1000 by 1990. That’s not many in a city of over 2 million, so I would agree that it’s probably an unstable situation there for the species. The equatorial belt is the only zone they’ve really failed to conquer properly.

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

                Comment


                • #9
                  Couple of interesting points:

                  Originally posted by cpbell View Post
                  House Sparrows are soooo last decade, but anyone still interested in why they disappeared might want...
                  They haven't disappeared - that's overstating the 'problem'. They have simply declined in numbers and range relative to some arbitrary point in the past. There are still millions of them.

                  Originally posted by cpbell View Post
                  It supports my conjecture in the original Auk paper that urban sparrows were picked off because they had lost predator aversion.
                  This wasn't the biggest conjecture in the Auk paper. The whopper, in terms of guesswork/discussion, was that Sparrowhawks picked off sparrows in sufficient numbers to account for the decline. Without direct evidence based on sparrow mortality, this will always be just a guess (and hence why the prize wasn't won). Where there is direct field evidence of mortality, it is for chick starvation in the nest, which would undermine your conjecture about predation being the main driver. The Auk paper cannot account for that result, nor counter it with better field data.

                  The Auk paper can never get away from the fact that it is just a correlation, based on some datasets of questionable quality/suitability for the task. It was more interesting to me for the method than the result, which was hamstrung by the data issue (and failure to control for land use change and other temporal variables).

                  Originally posted by cpbell View Post
                  Do I gather that you agree that mesopredator release is a significant factor in the declines of small birds in Europe and other heavily farmed landscapes[plural species, numerous regions]? If so, would you agree that the RSPB led line that raptors etc. are totally innocent is a problem for conservation?
                  Agree with who? Based on what evidence? If it's an invitation to agree with CP Bell's conjecture in the Auk sparrow paper, then I'd decline, especially in light of this:

                  Originally posted by cpbell View Post
                  I should also remind you that I'm not asserting that any species apart from the House Sparrow have been affected by Sparrowhawks.
                  Because raptor predation is politicised, and could have important consequences, the bar for evidence is rightly set very high. Much higher than for many other problems in conservation, where you can more easily get away with a sweeping conjecture - I'd like to see the same bar across the board. But it means that a good scientist or academic, even a frustrated one, must remain objective and not form conclusions in the absence of that good evidence. It's ok to have a theory, but not to start with the conclusion and look for evidence to fit, ignoring that which doesn't (e.g. chick starvation). That's not good scientific method. It's also quite bad to abuse by name in public not only your co-authors but anyone else who has published on the subject and doesn't share your conclusion - which may explain the non-cooperation (although I understand the BTO data is available to CP bell from the BTO at the market rate [according to a youtube video he made], so that's not non-cooperation, that's unwillingness to pay.)
                  Last edited by mafting; December 7th, 2011, 11:54 AM.

                  Comment


                  • #10
                    Originally posted by cpbell View Post
                    Sensible comments for the most part, and just the kind of debate that is needed.
                    So why is it going on on surfbirds, youtube and birdforum, and not in the pages of Journal of Applied Ecology, like other scientific debates? Why not subject your opinions to standard peer review?

                    Comment


                    • #11
                      Originally posted by cpbell View Post
                      I’m often accused of being strident, but remember that the argument is me on one side and a mega-corp with a £100 million annual turnover on the other, and only a fool sticks to Queensberry rules while the other guy is kicking him in the nuts.
                      Its your narrative about 'mega-corps' and 'conservation industry' that doesn't help your cause...

                      Originally posted by cpbell View Post
                      So far as agri-environment schemes are concerned, I’m only quoting the bare facts concerning the Farmland Bird Indicator. The schemes are specifically designed to help this recover but it hasn’t happened, and the excuses get thinner every year that goes by.
                      I'm happy to accept that a rebounding population of Sparrowhawks represent an additive source of motality for many populations of already declining small passerines.

                      Clearly however Sparrowhawks can't be held responsible for the declines in invertebrate populations in agropastoral landscapes observed across the UK. This fact is I presume undisputable and coupled with land-use change surely the overwhelming driving factors in the declines of all farmland species?

                      Originally posted by cpbell View Post
                      The equatorial belt is the only zone they’ve really failed to conquer properly.
                      So, fair enough, boom-bust cycles in Amazonia probably a bad example.

                      Otherwise, I'd agree with everything RB said. Do you agree with my 'narrative' on our current raptor-politics situation?

                      What would your conservation interventions be?
                      Last edited by Alex Lees; December 7th, 2011, 06:43 PM.
                      Dept. of Zoology, University of Cambridge, UK

                      My website - Neotropical Bird Club -Tropical Forest Research - Punkbirder - Wikiaves

                      In natural science the principles of truth ought to be confirmed by observation. — Carolus Linnaeus

                      Comment


                      • #12
                        CPB - from your paper
                        It has been apparent for some time that the evidence for benefits to biodiversity of agri-environment schemes is weak (Kleijn & Sutherland 2003)
                        from Kleijn & Sutherland (2003)

                        Overall, 54% of the examined species (groups) demonstrated increases and 6% decreases in species richness or abundance compared with controls. Seventeen percent showed increases for some species and decreases for other species, while 23% showed no change at all in response to agri-environment schemes. The response varied between taxa. Of 19 studies examining the response of birds that included a statistical analysis, four showed significant increases in species richness or abundance, two showed decreases and nine showed both increases and decreases. Comparative figures for 20 arthropod studies yielded 11 studies that showed an increase in species richness or abundance, no study showed a decrease and three showed both increases and decreases. Fourteen plant studies yielded six studies that showed increases in species richness or abundance, two showed decreases and no study showed both increases and decreases.

                        I would say that you misrepresented the conclusions of that study. I know Bill wouldn't agree with you and if you follow Kleijn's other papers, e.g. Kleijn et al. 2009:

                        Worldwide agriculture is one of the main drivers of biodiversity decline. Effective conservation strategies depend on the type of relationship between biodiversity and land-use intensity, but to date the shape of this relationship is unknown. We linked plant species richness with nitrogen (N) input as an indicator of land-use intensity on 130 grasslands and 141 arable fields in six European countries. Using Poisson regression, we found that plant species richness was significantly negatively related to N input on both field types after the effects of confounding environmental factors had been accounted for. Subsequent analyses showed that exponentially declining relationships provided a better fit than linear or unimodal relationships and that this was largely the result of the response of rare species (relative cover less than 1%). Our results indicate that conservation benefits are disproportionally more costly on high-intensity than on low-intensity farmland. For example, reducing N inputs from 75 to 0 and 400 to 60 kg ha−1 yr−1 resulted in about the same estimated species gain for arable plants. Conservation initiatives are most (cost-)effective if they are preferentially implemented in extensively farmed areas that still support high levels of biodiversity.
                        which is in turn not neccesarily the case in the tropics, e.g.Mahood et al. (2011)

                        A lot of straw men in your paper, and moreover why didn't you cite some of the rich literature on predation - papers which talk of the synergisms between habitat loss and predation risk for example? Seems disingenuous to me.

                        Edit - this: http://www.ncl.ac.uk/biology/assets/...11JAppEcol.pdf worth a read.
                        Last edited by Alex Lees; December 7th, 2011, 07:17 PM.
                        Dept. of Zoology, University of Cambridge, UK

                        My website - Neotropical Bird Club -Tropical Forest Research - Punkbirder - Wikiaves

                        In natural science the principles of truth ought to be confirmed by observation. — Carolus Linnaeus

                        Comment


                        • #13
                          Originally posted by mafting View Post
                          This wasn't the biggest conjecture in the Auk paper. The whopper, in terms of guesswork/discussion, was that Sparrowhawks picked off sparrows in sufficient numbers to account for the decline. Without direct evidence based on sparrow mortality, this will always be just a guess (and hence why the prize wasn't won). Where there is direct field evidence of mortality, it is for chick starvation in the nest, which would undermine your conjecture about predation being the main driver. The Auk paper cannot account for that result, nor counter it with better field data.
                          First of all, it’s generally agreed that the demographic mechanism for sparrow decline has been a decline in adult and particularly first year mortality (as would be expected if raptor predation were the cause). In the Auk paper I developed a population model with an empirically derived intrinsic rate of increase, and an assumption that Sparrowhawks take 20-30% of local sparrows in a given year. This produces an annual population decrease of 7%, which closely matches the observed trend at locations across Britain following re-establishment of Sparrowhawks.
                          Rural Sparrows typically reach densities of 30 per km2, and urban sparrows 300 per km2, so for a typical Sparrowhawk hunting territory of 4km2 there is a population of 120 sparrows in rural areas, and 1200 in urban areas. To cause 30% mortality, a rural hawk pair would have to take 30 sparrows, and an urban pair 300. Unlikely? Actually no, since Sparrowhawks in newly colonised urban areas have been seen to bring back to the nest up to 400 sparrows in a season. Sparrowhawks do indeed pick off sparrows in sufficient numbers to cause the decline. Indeed, our best guess as to how many they pick off would reproduce precisely the decline observed in all its temporal and geographic detail.

                          The model developed by Peach in his Animal Conservation paper, which factors in chick mortality observed in Leicester by Vincent, predicts an INCREASE in breeding success over the period of sparrow decline, and the pattern of increase predicted closely matches that derived from nest records over the period. Breeding success CANNOT therefore be the cause of sparrow decline, hence the casuistry on the part of RSPB/BTO about the role of density dependent breeding success in stabilizing sparrow populations.

                          Originally posted by mafting View Post
                          It's ok to have a theory, but not to start with the conclusion and look for evidence to fit, ignoring that which doesn't (e.g. chick starvation). That's not good scientific method.
                          If you think the Auk paper starts with a conclusion and then looks for evidence to fit, you really have not understood it. It begins with a clearly stated hypothesis, which enables predictions to be derived which are precise and, importantly, improbable in the event that the hypothesis is untrue. In other words it is hypothetico-deductive science, and the deduced predictions are fulfilled in every detail. It’s my opponents who are guilty of trawling for evidence to fit their conclusion, and despite the huge resources at their disposal, they’ve been unsuccessful. Instead they’ve resorted to hand waving and statistical sleight of hand, allied to a concerted campaign of disinformation that has led to and extraordinary waste of resources on ineffective conservation initiatives.

                          Originally posted by mafting View Post
                          It's also quite bad to abuse by name in public not only your co-authors but anyone else who has published on the subject and doesn't share your conclusion
                          For instance?

                          Originally posted by mafting View Post
                          - which may explain the non-cooperation (although I understand the BTO data is available to CP bell from the BTO at the market rate [according to a youtube video he made], so that's not non-cooperation, that's unwillingness to pay.)
                          Like most markets, this one is rigged in favour of one party. The BTO are not in a free market in any sense - how much do they pay their volunteers for the data they they’re so keen to sell to the highest bidder? And what about the half million a year they receive from the taxpayer for data curation? Does that not make their data a public good that should be available on demand? They are taking their volunteers for a ride, and hoarding the data to conceal any evidence that might affect their ability to chisel more money out of the government. Like I’ve said elsewhere, I can’t afford the asking price, but even if I could there’s no way I would pay these people for the privilege of doing their job for them.

                          Originally posted by mafting View Post
                          So why is it going on on surfbirds, youtube and birdforum, and not in the pages of Journal of Applied Ecology, like other scientific debates? Why not subject your opinions to standard peer review?
                          You might want to take another look at post #1 in the thread.
                          Originally posted by Alex Lees View Post
                          I'm happy to accept that a rebounding population of Sparrowhawks represent an additive source of motality for many populations of already declining small passerines.
                          It’s clear from the analysis in the Auk paper that House Sparrows were stable before the return of Sparrowhawks, and failing BTO intransigence we would know if this were also the case for a dozen other farmland species. As it is I can only cite the ‘signature’ mid-1970s downturn of so many farmland species, which were not declining before Sparrowhawks flooded back into the British lowlands. As for the agriculture-predation interaction trope, I’ve no doubt the RSPB have well laid plans to use this as a fall-back position. You’ve also linked to a paper by Whittingham – I’ll try to read it, but forgive me if I don’t put it to the top of my list – my previous sampling of his oeuvre falls firmly within the ‘time wasted’ category.

                          Originally posted by Alex Lees View Post
                          Clearly however Sparrowhawks can't be held responsible for the declines in invertebrate populations in agropastoral landscapes observed across the UK. This fact is I presume undisputable and coupled with land-use change surely the overwhelming driving factors in the declines of all farmland species?
                          I accept that insecticides kill insects if that’s what you mean. However I’m not convinced by the overall ‘insects have declined’ narrative. Benton et. al. tends to come up a lot, despite being unconvincing, and there’s always a lot of talk about insects on radiator grills. Perhaps you’ll enlighten me however?

                          Originally posted by Alex Lees View Post
                          from Kleijn & Sutherland (2003)
                          I would say that you misrepresented the conclusions of that study.
                          The point Kleijn & Sutherland were making was that agri-schemes had not been thoroughly evaluated. Does this not mean that evidence for their efficacy is necessarily weak?

                          Originally posted by Alex Lees View Post
                          I know Bill wouldn't agree with you and if you follow Kleijn's other papers, e.g. Kleijn et al. 2009:
                          So use of Nitrogen fertilizer on grassland reduces plant diversity. I do remember that from Ecology 101 – but your point is?

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

                          Comment


                          • #14
                            Originally posted by cpbell View Post
                            First of all, it’s generally agreed that the demographic mechanism for sparrow decline has been a decline in adult and particularly first year mortality (as would be expected if raptor predation were the cause).
                            Or if starvation of juvs was the case due to lack of autumn/winter food.

                            Originally posted by cpbell View Post
                            In the Auk paper I developed a population model with an empirically derived intrinsic rate of increase, and an assumption that Sparrowhawks take 20-30% of local sparrows in a given year. This produces an annual population decrease of 7%, which closely matches the observed trend at locations across Britain following re-establishment of Sparrowhawks.
                            Rural Sparrows typically reach densities of 30 per km2, and urban sparrows 300 per km2, so for a typical Sparrowhawk hunting territory of 4km2 there is a population of 120 sparrows in rural areas, and 1200 in urban areas. To cause 30% mortality, a rural hawk pair would have to take 30 sparrows, and an urban pair 300. Unlikely? Actually no, since Sparrowhawks in newly colonised urban areas have been seen to bring back to the nest up to 400 sparrows in a season. Sparrowhawks do indeed pick off sparrows in sufficient numbers to cause the decline. Indeed, our best guess as to how many they pick off would reproduce precisely the decline observed in all its temporal and geographic detail.
                            The problem isn't the model, it's the assumptions and the datasets you used. In particular, your model used spatio-temporal cetegories which had some very small sample sizes (some well below 10 sample points). Fundamentally, you modelled spatio-temporal change in birds but not habitat - your urban/rural cetegories contained no check of temporal change whatsoever, which compounds the small sample sizes. Thirdly, the garden birdwatch data is dodgy - it is a crude count of maximum number seen at any one time, which is not the same as number present. For instance, the same dataset shows a long-term decline in Blue Tits, whereas we know from every other index that this is spurious bull..... You have no way of knowing if the sparrow data is similarly flawed, or by how much. Finally, the Sparrowhawk recovery map is extremely broad resolution (masquerading as a smoothed continuous surface within smoothed bounding regions), which further compounds your small sample sizes. So whatever answer pops out the back of a model based upon these datasets is really not the sort of thing that you want to hold up as a solid result and stake your reputation.

                            The polarisation of Bell and the RSPB can be summed up as Bell correlating a decline in sprrows with a demonstrable increase in Sparrowhawks, and the RSPB correlating a decline in saprrows with a demonstrable decrease in food supply. The problem for Bell is that the pattern of Sparrowhawk recovery is the same as the pattern of agricultural intensfication, which means that his spatio-temporal approach (however flawed) cannot be decoupled from food supply. As Bell's Auk paper is essentially just a correlation of one thing happening in time and space while the inverse of another thing happens in time and space, but without a demonstrated causal link (his 'evidence' of predation and mortality were estimates), this means that we could possibly get the same result if we replaced Sparrowhawks in the model with anything else that showed a similar rough-and-ready spatio-temporal pattern of northwest-to-southeast - such as phenology of daffodil blooms, incidence of bird tables (which may act as a disease vector) or even mobile phone usage. No matter how hard he tries, and note he lacks any tangible public support from his co-authors (we can assume Dan Chamberlain disowns the Auk paper), he cannot overcome the fact that it's just a correlation in a model full of numbers that he has selected to input. It would be interesting to know if any other iterations were performed before the best set of estimates were selected, but that would be unfair to speculate. It is also unfair to speculate how the paper was funded, as there was no funding acknowledgement (unusually).

                            Originally posted by cpbell View Post
                            The model developed by Peach in his Animal Conservation paper, which factors in chick mortality observed in Leicester by Vincent, predicts an INCREASE in breeding success over the period of sparrow decline, and the pattern of increase predicted closely matches that derived from nest records over the period. Breeding success CANNOT therefore be the cause of sparrow decline, hence the casuistry on the part of RSPB/BTO about the role of density dependent breeding success in stabilizing sparrow populations.
                            Which just goes to show you the limitations of models such as yours and Peach's in a relative data vacuum, where you're trying to join pin-prick dots of data with a the modelling equivalent of an 8" paintbrush.

                            Originally posted by cpbell View Post
                            If you think the Auk paper starts with a conclusion and then looks for evidence to fit, you really have not understood it.
                            Such a putdown may work for the Birdforum Intelligenstia (your words), but not here. I did not claim that for the paper, which I found interesting for its method, with a provocative and fairly brave conjecture in the discussion. No, I implied that the lead author starts his internet argument with the conclusion. I notice that there is a big difference between what you say in the Auk paper (couched in caveats and conjecture) and how you state your case on Birdforum, Surfbirds, youtube and Talking Naturally. The reason you couldn't use the latter bullish approach and strong claims in Auk is that they cannot leap the scientific bar - they're just your (largely) unsupported opinion. But outside the Big School of peer review, in the internet playground, your claims are much stronger because you know teacher can't stop you and say "that's an unsupported claim, young Bell!" and clip your ear. So what that seems to be, is an attempt to circumvent peer review, and an attempt to make claims of fact without being challenged by those qualified to do so in the accepted forum for such. You have essentially selected the same platform to disseminate your scientific theories as David Ike.

                            Originally posted by cpbell View Post
                            Instead they’ve resorted to hand waving and statistical sleight of hand,
                            This is a little rich when your Auk paper uses sample sizes of well under 10 to model national trends, and claim spatio-temporal rigor when your habitat data consisted of a single point in time.

                            Originally posted by cpbell View Post
                            For instance?
                            A read through the Birdforum thread shows you've named numerous people in disparaging terms, such as Will Peach, Dan Chamberlain and Ian Newton, who you accused of being in it mainly for the money.

                            Originally posted by cpbell View Post
                            Like most markets, this one is rigged in favour of one party. The BTO are not in a free market in any sense - how much do they pay their volunteers for the data they they’re so keen to sell to the highest bidder? And what about the half million a year they receive from the taxpayer for data curation? Does that not make their data a public good that should be available on demand?
                            This is astonishing. What you are saying here is that you want free access to a product that is knowingly donated by fee-paying members and other volunteers, and held by a charity that accepts paid work from the taxpayer. By the same logic, I suppose you feel entitled to help yourself to the bookshelves of the Camden branch of Oxfam? Both Oxfam and the BTO are charities that accept donations of time/work/goods by members and non-members alike, and also accept funds from the UK Govt (DFID and defra, respectively).

                            You are essentially demanding that data donated to the BTO is given to you free of charge, to do whatever you like, without any knowledge or consent of the BTO volunteers and without any gain for the organisation they have chosen to support. So you want all the benefits and infrastructure of a large membership-based organisation, and the support of its 100 staff and 15,000 volunteers, without contributing anything at all to that organisation? I suppose you also want the BBC to waive your TV licence, the NHS to treat you without paying National Insurance, and the RSPCA to walk your dog?

                            Originally posted by cpbell View Post
                            It’s clear from the analysis in the Auk paper that House Sparrows were stable before the return of Sparrowhawks,
                            No it isn't, not based on that garden birdwatch data. You can suggest it, but I wouldn't bet a career on it, when it shows such anomalies as the Blue Tit trend.
                            Last edited by mafting; December 7th, 2011, 11:54 PM.

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                            • #15
                              Originally posted by cpbell View Post

                              "Originally Posted by mafting
                              It's also quite bad to abuse by name in public not only your co-authors but anyone else who has published on the subject and doesn't share your conclusion"

                              For instance?
                              From here: http://www.birdforum.net/showthread.php?p=2009158

                              CP Bell states: "To understand the silence from the likes of Peach, Newton et al. you really have to get inside the mind of a professional ornithologist. To most amateur enthusiasts, it probably seems like about the best thing you could possibly do. However the truth is, once you’ve got your feet under the table, it becomes pretty much like any other job, and your priorities are simply getting through the day, paying off the mortgage, putting the kids through school, just like everybody else. All thoughts of solving the great mysteries of nature soon become a distant memory.

                              Against this background the ‘professional’ mentality takes over. You want to hear Peach’s opinion? Put your hand in your pocket. You want to catch the pearls of wisdom dripping from the lips of Newton? Insert your debit card here."

                              and:

                              "The Peach/Vincent, Chamberlain and Wilkinson studies exemplify the ascientific approach used to support the urban Sparrow decline narrative that the conservation industry has sought to establish. They have not erected clear hypotheses, nor have they derived improbable predictions and subjected them to critical tests. Instead they’ve sought broad correlations, which are very likely to be spurious, and presented these in aggregate as a ‘weight of evidence’ in favour of their rationalisations. The background to this is that urban Sparrow declines spoil the ‘agricultural intensification’ narrative of bird declines since there’s no agriculture in cities. This means that another, quite separate reason for urban Sparrow declines has to be found, because if urban and rural Sparrows are declining for the same reason, it isn’t agricultural intensification."

                              and:

                              "You could also look at the paper by Shaw, who was a BTO supervised PhD student at Exeter and produced a wonderful hand-waving exercise on the back of Chamberlain’s crazed scribblings, reading all manner of significance into the habits of the kinds of people who live in ‘back to back’ housing, though she obviously has no idea what this is. "

                              I think that supports my assertion.

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