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Thread: All quiet on the sparrow front

  1. #1
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    Default 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

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    Default 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!

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    Quote 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

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    Senior Member Alex Lees's Avatar
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    Quote 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

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    Quote 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

  7. #7
    Senior Member Alex Lees's Avatar
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    Quote 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.

    Quote 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.
    Quote 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

  8. #8
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    Quote 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.

    Quote 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 Ł100 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.

    Quote 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

  9. #9
    Senior Member mafting's Avatar
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    Couple of interesting points:

    Quote 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.

    Quote 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).

    Quote 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:

    Quote 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 at 11:54 AM.

  10. #10
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    Quote 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?

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