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

[occasional]

Your hypothesis seems to be that sparrows respond with such alacrity to the appearance of sparrowhawks that negligible mortality occurs, but their local ranges are then restricted, resulting in density dependent reduction in breeding success, which then causes a population decline which relieves the density dependent breeding depression. This is not impossible, but then you would have to explain why there has been a decline in adult and first year survival over the period of the decline (also in the withdrawn BTO report). In short we have a sparrowhawk-related population decline in tandem with a decline in adult/first year survival, and no evidence of decline in breeding success temporary or otherwise.

As far as I am concerned it is not my hypothesis, but rather your hypothesis, modified to take into account information which can be gleaned from contributions to this board.

You have then exagerrated the hypothesis by adding such expressions as "negligible mortality". If adult survival has declined, I, at least, am quite happy with that being part of "the sparrowhawk effect" and indeed it is what I would expect to find.

To put it simply, if one can find a hypothesis which appears to be consistent with all the evidence, both scientific and anecdotal, then that is the hypothesis which I would prefer to defend.

 

[Andrew Rowlands]

... my next research project will be on the migratory behaviour of trolls, to find out why flocks of them seem to mysteriously appear, then disappear again for no apparent reason.

Where are you having the GPS implant fitted?

 

[Apodemus]

Oh and by the way, my next research project will be on the migratory behaviour of trolls, to find out why flocks of them seem to mysteriously appear, then disappear again for no apparent reason.

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

Odd behaviour to keep labelling long-established members of this forum as trolls.

 

[CPBell]

Where are you having the GPS implant fitted?

The place they talk out of, where else?

 

[cates]

The article claims the source is research from the BTO and Cambridge University. Given the spin that the press applies to research results it would be wise to track down the original report and see what it actually says. Even if the Sparrowhawk population has quadrupled since its pesticide induced nadir (as claimed), I'd guess it's still no greater than in the 1940/50s so why weren't sparrow populations similarly depressed? The fact that both sparrows and sparrowhawks were common at that time needs explaining. No, I'd suggest sloppy science or sloppier reporting is at the root of this claim,

hi, most, if not all, species that are no longer around, declined at around or soon after the advent of organo-phosphate agricultural chemicals. the rspb. seems to have a policy of sweeping this one under the floor-boards; the carpet doesn't even come into it.

 

[Nature__lover]

Personally I think it will have more to do with the fact we treated them as pests for years. Some people even used to eat them.natural habitats are being replaced with roads and cities. the increase of pesticides must have taken it's toll too.

And we must remember nature is nature- survival of the fittest!

 

[spencer f]

I was wondering about predator averse behaviour today. I've noticed that the robin in my garden like many others is a very bold and seemingly tame creature. Sparrows used to have a simular reputation, so I was wondering why sparrows have lost their boldness and robins have retained it?

Also I've heard thoat house sparrows are kean on white millet, does anyone have expierience of this, most birds just ignore it. I've conducted a little experiment by filling seperate feeders with red & white millet, wheat, cannary seed, black sunflower mixed with hearts. With mainly finches and tits visiting the sunflower wins every time with the others not being touched apart from the cannary occasionaly.

 

[occasional]

Sparrows used to have a simular reputation

I am not sure that this is strictly true.
Had you tried to catch them as a child I think you would have found that sparrows are exceptionally risk averse ( or perhaps I am simply older than you ).

 

[spencer f]

Prehaps your right, I'm just going on stories I've heard. I'm also astonished at sights like those sparrows beig hand fed at Notredame cathedral and the famous pictures of Hedges Bates 'The Bird Man Of London' surrounded by sparrows in Hyde Park.

 

[MJB]

Prehaps your right, I'm just going on stories I've heard. I'm also astonished at sights like those sparrows beig hand fed at Notredame cathedral and the famous pictures of Hedges Bates 'The Bird Man Of London' surrounded by sparrows in Hyde Park.

I think the fundamental difference between House Sparrow and Robin behaviour is that the sparrows flock, and so nervousness by one individual obtains a flock reaction, thus making them difficult to approach. Robins, being soiltary for most of the year, make up their own minds, and so are known, in the UK, as confiding birds, whereas on the European Continent they exhibit skulking behaviour. I once lived in Germany for a few years, and it took me ages to persuade the Robin whose territory included my garden not to flee as soon as anyone entered the garden.

The Notre Dame sparrows and those in Hyde Park probably exhibit leant behaviour from previous generations, the original confiding birds likely having been few in number. Almost horses for courses, reall.
MJB

 

[London Birder]

Some Hyde Park / Kensington Gardens House Sparrow census figures;

Nov 1925: 2,603
Dec 1948: 885
Nov 1966: 642
Nov 1975: 544
Feb 1995: 46

'The reasons speculated for the national decline - changes in farming practices and increased number of predators, including Sparrowhawks - do not seem to apply to the parks unless the population, considered by some as largely sedentary, does require an injection of birds from outside London. The decline in horse traffic after 1925 has also been suggested as a possible factor'. (Sanderson. 1995).

My last sighting was of a single in 2006 though four birds were reported in January 2010 on one of the areas set aside for the RSPB's House Sparrow project. These areas now appear to be defunct from what I can see.

As for Sparrowhawk; a pair probably breed annually (but ascertaining this has been surprisingly difficult). Sanderson states that there wasn't a single record of this species between 1953 and 1975 (though this in part will be down to observer coverage) and only seven records between 1975 and 1995.

 

[MJB]

Some Hyde Park / Kensington Gardens House Sparrow census figures;

Nov 1925: 2,603
Dec 1948: 885
Nov 1966: 642
Nov 1975: 544
Feb 1995: 46

'The reasons speculated for the national decline - changes in farming practices and increased number of predators, including Sparrowhawks - do not seem to apply to the parks unless the population, considered by some as largely sedentary, does require an injection of birds from outside London. The decline in horse traffic after 1925 has also been suggested as a possible factor'. (Sanderson. 1995).

Are there any figures for domestic/feral cat density over the same period?
MJB

 

[spencer f]

Good points MJB. I notice that sparrows are quite bold when theres good cover around but are still quite nervous of humans, I find this odd since they live alongside us. Even the goldfinches in my garden will feed quite happily just a few yards away from me.

 

[London Birder]

Are there any figures for domestic/feral cat density over the same period?
MJB

None that I'm aware of though I can say that I've never seen a single one over the 625 acres in eight years birding the site (usually in excess of 100 site visits per year), though I dare say they occur.

 

[spencer f]

Regarding public parks, where did these sparrows nest, I suspect in the houses surrounding them, how are they now maintained, and how these parks are now managed (hedges, shrubberies etc)

 

[CPBell]

As for Sparrowhawk; a pair probably breed annually (but ascertaining this has been surprisingly difficult). Sanderson states that there wasn't a single record of this species between 1953 and 1975 (though this in part will be down to observer coverage) and only seven records between 1975 and 1995.

I don’t think there’s any disagreement that the sparrow crash between the 1920s and 40s was caused by the disappearance of horse-drawn transport, and the figures for ’48, ’66 and ’75 are probably within the margin of error, so it can’t be inferred that the decline continued through this period.

The 1995 autumn count for sparrows in Kensington Gardens for was 81, which was an 85% drop from the 1975 figure (no counts were done in the interim). Breeding by sparrowhawk in the grounds of Kensington Palace (which adjoins Kensington Gardens) was first confirmed in 1995, but they had been breeding in nearby Holland Park and Regent’s Park since at least 1993.

Credit where it’s due, Roy Sanderson was practically the first to hint at the idea that sparrowhawks might be contributing to sparrow decline, though I think he recanted when shown the instruments of torture. Here’s an extract from his article in the 2000 London Bird Report:

“The House Sparrow, a versatile species, used to be found in all habitats in the park, predominantly where they were likely to be fed by the public…For some time sparrows in the park have rarely waited out in the open for the public to throw bread for them. When they do take food, they come out of the shrubberies and shoot back into cover immediately afterwards, certainly not the tame behaviour of the traditional sparrow. This change suggests concern about predation. A few sparrows, seen during 2000 under the glass canopy of the Hay’s Galleria on the south bank of the Thames, were still tame, feeding under the chairs and tables of diners and perching out in the open. Clearly the canopy protects them from predators. The change of behaviour in Kensington Gardens seems to have coincided with the arrival of the Sparrowhawk, early in the 1990s.”

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

 

[London Birder]

Regarding public parks, where did these sparrows nest, I suspect in the houses surrounding them, how are they now maintained, and how these parks are now managed (hedges, shrubberies etc)

In Hyde Park / Kensington Gardens (from Sanderson. 1995);

'The number of potential nest sites has certainly declined. Tree holes, also used extensively by other species, are far fewer following the loss of many hundreds of the older trees to disease and strong winds and many old buildings, like the shelter on Buck Hill which used to have some 50 House Sparrow nests under the eaves, have been renovated'. A nesting colonoy of this species on a hawthorn was described as showing 'weaver bird characteristics'.

'On the basis of the 1967 census during the breeding season the number of breeding pairs was estimated at 160'.

 

[Cleme]

Sparrowhawk took a blackbird from our Wiltshire garden today - we think it must be the first time as it took him a day or two, and a few goes, to work out how to cope with dodging in and out of our fences...

It'll be interesting to see if he keeps coming back... I'd have to say that given the amount of sparrows/blackbirds/robins we've got it would be surprising if he didn't.

 

[London Birder]

Credit where it’s due, Roy Sanderson was practically the first to hint at the idea that sparrowhawks might be contributing to sparrow decline, though I think he recanted when shown the instruments of torture. Here’s an extract from his article in the 2000 London Bird Report:

“The House Sparrow, a versatile species, used to be found in all habitats in the park, predominantly where they were likely to be fed by the public…For some time sparrows in the park have rarely waited out in the open for the public to throw bread for them. When they do take food, they come out of the shrubberies and shoot back into cover immediately afterwards, certainly not the tame behaviour of the traditional sparrow. This change suggests concern about predation. A few sparrows, seen during 2000 under the glass canopy of the Hay’s Galleria on the south bank of the Thames, were still tame, feeding under the chairs and tables of diners and perching out in the open. Clearly the canopy protects them from predators. The change of behaviour in Kensington Gardens seems to have coincided with the arrival of the Sparrowhawk, early in the 1990s.”

I had this convo with Roy and I wouldn't disagree. I remember seeing sparrows 'dust'-bathing in a sugar bowl on one of the tables at the Serpentine Restaurant back in the '70s. Unfortunately I never birded the site during such time as their behaviour changed, nor during the arrival of Sparrowhawks.

Do you have any info on recruitment into isolated urban populations from outside of the area? The remaining Inner London sector birds seem very sedentary in my experience.

 

[CPBell]

Do you have any info on recruitment into isolated urban populations from outside of the area? The remaining Inner London sector birds seem very sedentary in my experience.

I don't think there is any, if you mean exchange between the isolated central London populations and the more contiguous populations in the suburbs. I put colour rings on the London Zoo population, but we never had a single sighting outside the zoo, which is not surprising since they are hardly ever even seen in Regent's Park. I checked a nearby colony in Primrose Hill a few times but never saw any ringed birds there.

Perhaps we'll find out when we see the results of the massive London-wide sparrow research projects carried out by the RSPB over the past few years, about which they seem remarkably quiet.