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

[CPBell]

Earleybird, King Edward

Please excuse my mumbling - I meant to say that many hedges are now 'managed under agri-environment schemes'.

My point really is that in both urban and rural environments, it's extremely difficult to objectively measure habitat suitability. It's easy to point to a change and say look, that's made the environment worse and it's proved by the fact that species x has gone down. This is a circular argument, however. There are both beneficial and detrimental changes going on all the time in complex environments like farmland and urban settlements, any of which can be argued to cause population increase in species x, or decrease in species y.

Rest assured also that there's nothing sinister in my reference to a 'solution'. I just meant a solution to the conundrum of why sparrows have declined. I'm purely a scientist rather than a conservationist - I just want conservation to be informed by science rather than the other way round.

http://www.youtube.com/CultoftheAmateur

 

[Amarillo]

Can't be bothered going through the whole thread...this is complete nonsense right?

The decline in house sparrows is certainly a very interesting issue, but the idea that sparrowhawks are anything other than a minor contributing factor just doesn't add up. There are a lot more sparrowhawks than there were, but nowhere near enough to have a significant effect on the numbers of a bird as abundant as sparrows.

 

[jacksnipe]

I agree with you chrisKten.thanks.

 

[Motmot]

Valencia area
http://www.informaworld.com/smpp/content~content=a924951983~db=all~jumptype=rss
http://www.ardeola.org/files/ardeola_500.pdf ,summary in english.

Could not find anything linkable from Madrid but SEO-Birdlife says this city is losing around 14.000 House Sparrows every year (don't know how they reached that result though).
Ringing at the Parque del Oeste (Madrid) showed a massive decline (from 200 average birds per year to 5).

Valladolid
http://www.livingplanet.be/Balmori_and_Hallberg_EBM_2007.pdf

Cheers

 

[spencer f]

Amarillo

I am inclined to agree with you, but what makes you so certain?

 

[spencer f]

CPBell

The RSPB will never support a theory that a bird is responsible for the demise of another, especially a Sparrowhawk. There would be uproar, the Rspb would rapidly loose membership. I have to say that the RSPB have some excellent programmes, the 'Homes For Wildlife' in particular can only do good in my opinion.

Whatever theory you support, the creation of extra cover and supplementry feeding would still be a prescription for it.

 

[mjh73]

Thankfully the RSPB employs scientists and ecologists who look at the facts ,
The fact is that, in nature, birds can be responsible for the decline of other birds. If need be the RSPB is more than capable of managing a common bird to save a threatened one, although I agree in a case as high profile as this they would need rock solid evidence, and I suspect would still baulk at controlling sparrowhawks. Anyway, I thought the indication from the research was that numbers of sparrows were now stabilizing, in which case action might be un-necessary.
I'm not sure where this thread is going. No one seems to agree with C P Bell, but in the absence of some research that proves the contrary he is obviously very confident in his outcomes.

mjh

CPBell

The RSPB will never support a theory that a bird is responsible for the demise of another, especially a Sparrowhawk. There would be uproar, the Rspb would rapidly loose membership. I have to say that the RSPB have some excellent programmes, the 'Homes For Wildlife' in particular can only do good in my opinion.

Whatever theory you support, the creation of extra cover and supplementry feeding would still be a prescription for it.

 

[King Edward]

To look at the question from another angle, how does today's Sparrowhawk population compare to the population and distribution before the decline caused by pesticides? Is there much known about the numbers of Sparrowhawks and House Sparrows / farmland birds prior to WWII? I'm not thinking so much about towns here but about the wider countryside.

With regard to agricultural intensification, just because changes in habitat quality are difficult to measure objectively it doesn't mean that they can be ignored as a factor. The British countryside changed massively over the 20th century, and will no doubt continue to change, and it just isn't plausible that there haven't been substantial effects on birds and other wildlife, even if attribution of the effects is difficult.

 

[spencer f]

If need be the RSPB is more than capable of managing a common bird to save a threatened one,
mjh

I have great respect for the RSPB so please don't take this the wrong way, but do you have an example?

 

[mjh73]

I have great respect for the RSPB so please don't take this the wrong way, but do you have an example?

Yes, from when I worked on the voluntary wardening scheme in the 1990s. In fact the RSPB aknowledges this on it's website:
http://www.rspb.org.uk/advice/gardening/unwantedvisitors/predators_and_prey/controlling_predators.aspx

I suppose the question is this. If a species has become super-abundant because of human influence, to the detriment of a threatened species, should we intervene?
My answer would be that yes, to maintain biodiversity and protect a species from extinction we should consider intervening but only on the basis of sound scientific analysis.
I know some on here will disagree....

 

[CPBell]

Valencia area
http://www.informaworld.com/smpp/content~content=a924951983~db=all~jumptype=rss
http://www.ardeola.org/files/ardeola_500.pdf ,summary in english.

Could not find anything linkable from Madrid but SEO-Birdlife says this city is losing around 14.000 House Sparrows every year (don't know how they reached that result though).
Ringing at the Parque del Oeste (Madrid) showed a massive decline (from 200 average birds per year to 5).

Valladolid
http://www.livingplanet.be/Balmori_and_Hallberg_EBM_2007.pdf

Cheers

Thanks, I was aware of the Murgui and Balmori papers, but not the one by Gil-Delgado. The other thing we require is information about Sparrowhawks. They do seem to breed in the vicinity of Madrid, Valladolid and Valencia - how certain can we be that they haven't increased and/or penetrated urban areas at the same time as sparrow declines are occurring?

 

[Motmot]

"how certain can we be that they haven't increased and/or penetrated urban areas at the same time as sparrow declines are occurring?"

Afaik this hasn't happened in spanish cities. Possibly a few birds can be found in parks (surely only very few in Madrid or Valencia) but they can't be blamed for those big declines.
Something bad is happening to our sparrows; lack of good habitat, pollution, radiation, who knows, but sparrowhawks...
All this sounds to me like what many spanish hunters think of the Bonelli's Eagle. It's spanish name is Águila Perdicera (eagle that eats partridges) so they are regularly blamed for low numbers in Red-legged partridges. They often get shot and culling is frequently demanded. Hmmm...

 

[spencer f]

Yes, from when I worked on the voluntary wardening scheme in the 1990s. In fact the RSPB aknowledges this on it's website:
http://www.rspb.org.uk/advice/gardening/unwantedvisitors/predators_and_prey/controlling_predators.aspx

I suppose the question is this. If a species has become super-abundant because of human influence, to the detriment of a threatened species, should we intervene?
My answer would be that yes, to maintain biodiversity and protect a species from extinction we should consider intervening but only on the basis of sound scientific analysis.
I know some on here will disagree....

Very informative thankyou.

 

[Amarillo]

Amarillo

I am inclined to agree with you, but what makes you so certain?

I'm not certain, but when someone comes up with a theory that goes against basic ecological principles then there needs to be a bit more to it than just sparrows declining + sparrowhawks increasing = sparrowhawks responsible for sparrows decline if it is to be taken seriously.

 

[CPBell]

To look at the question from another angle, how does today's Sparrowhawk population compare to the population and distribution before the decline caused by pesticides? Is there much known about the numbers of Sparrowhawks and House Sparrows / farmland birds prior to WWII? I'm not thinking so much about towns here but about the wider countryside.

"Before the second world war the Sparrowhawk was heavily persecuted by gamekeepers, but it made a considerable recovery when gamekeeping declined during the war, and it was increasing from about 1940. Around Oxted and Limpsfield one observer found 18 pairs breeding in 1948, which looks a remarkably high density by present standards. About this time it became a regular breeding bird as close to central London as Richmond Park, Wimbledon Common and occasionally Greenwich Park. It also attempted to breed on Hampstead Heath and even in inner London, at Holland Park"

(from Montier, D. 1977. Atlas of breeding birds of the London area)

With regard to agricultural intensification, just because changes in habitat quality are difficult to measure objectively it doesn't mean that they can be ignored as a factor. The British countryside changed massively over the 20th century, and will no doubt continue to change, and it just isn't plausible that there haven't been substantial effects on birds and other wildlife, even if attribution of the effects is difficult.

But agriculture is not being ignored - it's every other possible explanation of bird declines other than agriculture that is being ignored. There is a mountain of research on the effects of agriculture on bird populations, and billions has been spent on implementing their findings in the form of agri-environment schemes. Yet the Farmland Bird Indicator continues to flatline. Does that not raise a smidgeon of doubt in your mind?

Possibly a few birds can be found in parks (surely only very few in Madrid or Valencia).

Surely? Why?

 

[Motmot]

Surely? Why?

Check the spanish bird related publications (anuarios etc), or better still come to those cities and check it out for yourself. I promise we won't hide the sparrowhawks in cages.

 

[earleybird]

"Before the second world war the Sparrowhawk was heavily persecuted by gamekeepers, but it made a considerable recovery when gamekeeping declined during the war, and it was increasing from about 1940. Around Oxted and Limpsfield one observer found 18 pairs breeding in 1948, which looks a remarkably high density by present standards. About this time it became a regular breeding bird as close to central London as Richmond Park, Wimbledon Common and occasionally Greenwich Park. It also attempted to breed on Hampstead Heath and even in inner London, at Holland Park"

(from Montier, D. 1977. Atlas of breeding birds of the London area)

I'm not sure how breeding numbers during and shortly after the war have much bearing on the past decade or so since sparrows were noted to be in serious decline ?

London is a very small part of the UK and the date of Montier's observation is 30+ years old . How do we acount for sparrow decline in the rest of the UK ?

 

[CPBell]

Check the spanish bird related publications (anuarios etc), or better still come to those cities and check it out for yourself. I promise we won't hide the sparrowhawks in cages.

Thanks for the invitation - I'd love to galivant around Spain looking for Sparrowhawks, but I doubt whether anyone will pay for it. Failing that I think I'm still looking for my well documented exception.

I'm not sure how breeding numbers during and shortly after the war have much bearing on the past decade or so since sparrows were noted to be in serious decline ?

London is a very small part of the UK and the date of Montier's observation is 30+ years old . How do we acount for sparrow decline in the rest of the UK ?

This was a response to King Edward's query about the pre-war situation. Sparrowhawks numbers were relatively low pre-war, but then increased during and immediately after the war, before crashing in the 1950s. The post war increase was probably not so great as the 70s-80s increase. E.g. Sparrowhawks didn't manage to penetrate central London successfully in the post-war period.

For an explanation of sparrow decline across Britain as a whole I recommend you take a look at the powerpoint presentation on my Youtube channel.

 

[simple]

The farmland bird indicator continues to decline because there aren't enough of the right land management options out there, at the right scale and in the right places.

This is proven FACT - DEFRA acknowledge this, also the RSPB's own Hope Farm proves the point robustly, using simple land management that does not effect profit, the farmland bird index has risen 301% since RSPb aquired the farm. Now the question should be 'why can't we get more farmers to do the right things?'

Have a look at the farmland bird increases on Flamborough Head, where the RSPB advised the farmers there and helped them enter the governments two-tiered Environmental Stewardship Schemes, all of the headland is in HLS and Tree sparrows and Corn Buntings are increasing.

3 key things are missing from our countryside for birds; safe nesting sites, insect rich habitat and winter food - the RSPB, Natural England and BTO have proved how you can turn it around - getting it done is the perrenial problem when the farming lobby groups can't support or protect these funds when crunch time comes.

We all know whats needed - now we have to get it done!

 

[simple]

BTW - both Flamborough and Hope Farm have a number of Sparrowhawks last time I checked.