Who To Believe? (1 Viewer)

[Nightranger]

Hi Anthony,

You can have #125 because I predicted privately that this thread would degenerate to personal comments again. I am not picking on you BTW because you are not alone.

Ian

 

[Nightranger]

There can be endless amounts of theory in endless amounts of internet searches, but eventually it boils down to observation of what actually happens on the ground. And Stevie's experiences show that curtailing the Magpie population does work on the ground. And what's more, his experiences are backed up, up and down the country.

Hi Alan,

This is perilously close to a strawman argument and it is a little self-defeating because it infers that one bit of evidence must be rejected to believe whatever you want. What I can tell you is that researchers have specifically looked for any evidence that predators cause species declines but nothing is ever found. This should not surprise us that much if we look at predator behaviour. Tim Birkhead states that an average value for predation is around 10% of their total diet. Now if we express this as a function of time then something that seems more than coincidence occurs. 10% is the equivalent of 35-36 days every year and is it coincidence that this is close to the value for the period between hatching and fledging of magpies? Magpies have a single brood per year and significantly this is timed to coincide with the maximum number of nests (early breeding residents will be on 2nd broods, summer migrants and single brooders will be on 1st or only broods) being present. Put simply, nest predation takes a lot of effort and is simply not worthwhile for an omnivorous bird at any other time. This begs the question, are single brood birds the ones that are declining? No, thrushes and blackbirds are on middle broods at the time of peak nest predation and 1st and last broods are likely to go unmolested except to occasional opportunism. Significantly, complaints to this office peak during the period of magpies nesting and calls at other times during the summer are rare if not, unheard of. Stevie's observations are perfectly valid except they refer to the situation indicated by Anthony about breeding succes and not to any relationship to species declines. Young birds will swell the population for all species in late summer but mortality to all causes starts to eat at this until we reach the lowest point just prior to the start of the breeding season. Inevitably, if you remove the predators, the population of young birds will not reduce as quickly (although, reduce it will certainly do). I would be interested to know if anyone reporting this effect has evidence that the breeding pairs were up in subsequent years. Despite what some people will have us believe, unpaired birds do not number an equivalent of the breeding pairs and the absolute limitation on any species is the habitat (including food and nesting resources).

Ian

 

[James Lowther]

There can be endless amounts of theory in endless amounts of internet searches, but eventually it boils down to observation of what actually happens on the ground.

Sorry Alan, but I don't think that's fair. Those papers are not 'endless amounts of theory', rather they are based on 'observation of what happens on the ground'. The difference between the data presented in the papers, and the experiences related by Stevie, the Tom etc. are that the former has been systematically gathered, properly controlled, peer reviewed etc. etc.
Nature is highly complicated and there will always be apparent exceptions to every rule, but we have to rely on the best evidence to formulate our theories, and the best evidence will always be scientific, not anecdotal.

James

 

[John o'Sullivan]

The problem lies not with science but with individuals and sections of societys desire to hold onto what they are able to believe (or at least pretend to believe). Sometimes no amount of evidence or reasoned debate will change positions. Over time, cultural attitudes and beliefs change and accepted truths become outdated and no longer sustainable without appearing eccentric. The importance of this discussion (not just here but also in the wider world) is not to dissuade those with fixed positions but to try to influence the debate so that eventually people tackle the actual issues and not the self-evident half truths and simplistic misunderstandings or misrepresentations. The main purpose of the overall arguement (hence the selective publication of this study in the field magazine) is of course not essentially to do with magpies and songbirds but to attempt to hold onto the outdated principle of killing predators as a way of justifying this practice as a principal. This can then be applied in relation to raptors, foxes, corvoids etc. The times however are a changing and sooner or later the principal will be rejected. I look forward to this.

 

[me1000]

John,
do you really think that the landowners and keepers of our countryside i.e farmers and the gentry,will just sit back and let "bunny huggers" not my phrase you understand, dictate to them how to run their affairs?.
Do not fool yourself into believing that the U.K.will end up as a giant Nature Reserve at the moment farming is in decline but I can assure you in the near future it will be needed again.
Happy birding me

 

[Jane Turner]

Just an observation Magpie numbers in my area for some reason this year seem to have been lower than normal and the blackbird and thrush population have increased accordingly also the jays reared their nest this year (first time in three years) because the magpies left them alone ,which leads me to believe that in areas where magpies are in high numbers they do affect young bird survival I am no scientist and my observations may be only a small sample of the big picture but would affect my personal judgement on this subject

Jays of course never eat nestlings! Though that in itself is also an entrirely irrelevant issue!

I could just as easily show from my own records that the peak in Magpie numbers on the tetrads I survey also coincided with peaks in breeding pairs of Lesser Whitethroat and Stonechat and the decline in Song Thrush numbers is mirrored nearly perfectly by an increase in Mallard numbers. I would of course not suggest that these facts were in any way dependent on one another.

 

[Jane Turner]

The problem lies not with science but with individuals and sections of societys desire to hold onto what they are able to believe (or at least pretend to believe). Sometimes no amount of evidence or reasoned debate will change positions. Over time, cultural attitudes and beliefs change and accepted truths become outdated and no longer sustainable without appearing eccentric. The importance of this discussion (not just here but also in the wider world) is not to dissuade those with fixed positions but to try to influence the debate so that eventually people tackle the actual issues and not the self-evident half truths and simplistic misunderstandings or misrepresentations. The main purpose of the overall arguement (hence the selective publication of this study in the field magazine) is of course not essentially to do with magpies and songbirds but to attempt to hold onto the outdated principle of killing predators as a way of justifying this practice as a principal. This can then be applied in relation to raptors, foxes, corvoids etc. The times however are a changing and sooner or later the principal will be rejected. I look forward to this.

Absolutely John

I have zero expectation of altering AM's views one iota and to be honest it would be a terrible disappointment if he did. I just thought it was time to give people wanting to read the available evidence, an opportunity make their own minds up anf something to work with beyond Shooting Times hyperbole....or wherever it originated.

 

[me1000]

Shooting Times hyberbole ,
I will not retort as you wish that I would, Jane? my family tends my garden although it is only a few hundred acres and with 15 emplyees, how many acres do you look after in this green and pleasant land of ours??????
me

 

[Edward woodwood]

I give in folks

it's the magpies wot dun it guv.

I don't need to see any proof cos i knows it

Population dynamics? It's Humbug!

 

[John o'Sullivan]

So here we are at reply no 135. The answer to the original question as to Who To Believe is demonstrated in the responses. Ultimately people believe in what they choose and are taught/conditioned to. I choose to believe that the principle of attempting to control prey through culling predators has not been demonstrated to be effective. I also choose to believe that even if it had been, the end would not justify the means. There are structural reasons why e.g. songbird nos have been shown to decline adressing these is the way I would prefer this to be tackled. I also think that an understanding of this issue requires not just an ecological perspective but also a political, an economic, a psychological, a sociological, a philosophical, a spiritual and at least also and very importantly an historical perspective (I apologise to any specialists out there that have been missed off). The mistake with common sense understandings is they are often based on reductionism and localised impressions. As scientific justification for the effectiveness, value or intelligence of an intervetion they are frequently irrelevant. Finally I choose not to respond to this thread anymore as its going round in circles. I am glad however that there are people around who have got the energy to take the time to put forward more complex and coherent explanations as to why the reductionist arguements do not adequately explain how eco-systems actually inter relate. The more this permeates through society then over time, the more victorian understandings of ecological control will disappear.

 

[Edward woodwood]

yep John, very well said. I wish i had your patience...but i use it all up being nice to children all day at school.

lets hope you're right. I like your positive attitude
educashun is all wot we got after all

knowledge is power folks

g'night

 

[Jane Turner]

I choose to believe that the principle of attempting to control prey through culling predators has not been demonstrated to be effective. I also choose to believe that even if it had been, the end would not justify the means.

It would of course be a different debate if there was a prey species that had a population level way below the numbers that remaining habitat could support. Then I guess I'd prefer "barrier methods" if they were practical.

 

[Jane Turner]

I have some more references, but to be frank they are all saying much the same thing. I don't know about anything else, but to me it shows the value of all those breeding tetrad surveys which build up into the CBC. I expect many BF members have taken part over the years. Apart from anything else its great fun.... the highlight of my spring (and I flushed a Nightjar off the dunes of my local patch the same morning) was seeing a pair of Tree Sparrows disappearing into a hole in an old willow on a piece of land I'd never have visited had it not been part of one of my tetrads. I had not been able to prove that the species had bred since the mid 80's

Anyone looking for something constructive to do, consider joining in.

 

[Richard D]

“Would it matter to you, if your grannie had been eaten by a cannibal when she was 10 years old??”

...“so any analogy to bird population dynamics is of course spurious.”



Not so. That little songbird that was on your feeder today, had a “grannie”. If it’s grannie had been eaten prior to breeding, then that on your feeder would be an open space instead of a grandbird, or grandchild of the previous mentioned grannie, the bird that is, not your one.

...Quite easy. Draw up your family tree. Go back 6 generations if possible. Count the numbers of persons mentioned. Then note your direct descendants. At your Great Grandmother, put in a comment that she was eaten by a Magpie when she was a child in her pram. Then work out what happens to the family tree. Recount the numbers again. Quite easy to obtain a result.

...

As I stated in the part of the post you didn't quote, the reason the analogy is spurious is that as humans our population size is not constrained by natural habitat. It doesn't matter if a thrush, blue-tit, whatever is eaten by a magpie if there isn't enough habitat for it to survive in. Unless you ignore all the research that points to lack of habitat as being the limiting factor in songbird populations then natural predation of these birds is not a problem. If a bird produces five off-spring and there is only enough habitat to support one of those off-spring then the other four aren't going to survive anyway.

Regards Richard

 

[Nightranger]

As I stated in the part of the post you didn't quote, the reason the analogy is spurious is that as humans our population size is not constrained by natural habitat. It doesn't matter if a thrush, blue-tit, whatever is eaten by a magpie if there isn't enough habitat for it to survive in. Unless you ignore all the research that points to lack of habitat as being the limiting factor in songbird populations then natural predation of these birds is not a problem. If a bird produces five off-spring and there is only enough habitat to support one of those off-spring then the other four aren't going to survive anyway.

Regards Richard

Hi Richard,

I have been trying to explain this point for the last few days but I feel like I am banging my head against a wall now. It is clear that BF is infested with one or two people that have absolutely no interest in birdwatching. They may have a passing interest in birds and wildlife (mostly to kill it I suspect but that is not the point) and their sole reason for being here is to agitate. As John intimated, the thread title was a total blind for presenting certain opinions that have nothing to do with birding. The thread ran a familiar course with Jane and Anthony swatting each other with personal comments yesterday and ME bringing up the fluffy bunny point again. It would be funny if I had not predicted all this privately to Jane, Steve and oceans. So bets down for the next prediction. I said during the cormorant debate that it was the thin end of the wedge so I am now waiting for the debate on sawbills and herons. Why be selective? We have heard the so-called case against peregrines and sparrowhawks so what about merlins, hobbies, great spotted woodpeckers, weasels and stoats, badgers, squirrels and hedgehogs?

Ian

 

[Anthony Morton]

Hold on just a moment while we all catch our breath. I began this thread by referring to two earlier postings which appeared to me to be giving opposing answers to the same question. I did not express an opinion in any way, shape or form as to which one I felt was correct but instead invited members to put forward their views on the subject - and that's when the fight started!

Later on I quoted extracts from an article based on a scientific paper which appeared to contradict the opinion arrived at by most ecologists. Once again I quite deliberately expressed no opinion whatsoever on whether I agreed or disagreed with its contents but this did not stop some members behaving as though I had written the article myself - I didn't by the way!

Reams of factual evidence have been put forward, all supporting the accepted view but NOBODY seemed either prepared or able to address the merits (or otherwise!) of the one paper I had referred to. Even more interesting, perhaps, is that several of this paper's authors are well respected ecologists with numerous other papers to their credit all expressing the accepted view. So have these people perhaps changed their opinions, been misquoted, their findings taken ouit of context - or what?

Strangely it does now seem that some of the more recent postings are trying to discuss the original question I began this thread with. Better late than never I suppose!

Edit

I had posted the above before reading Ian's latest effort. For my part I will try not to disappoint him!

 

[Edward woodwood]

no

read the damn thing

and work it out for yourself

Tim

 

[Brian Stone]

Reams of factual evidence have been put forward, all supporting the accepted view but NOBODY seemed either prepared or able to address the merits (or otherwise!) of the one paper I had referred to. Even more interesting, perhaps, is that several of this paper's authors are well respected ecologists with numerous other papers to their credit all expressing the accepted view. So have these people perhaps changed their opinions, been misquoted, their findings taken ouit of context - or what?

Forgive me if I am wrong but I am sure it has been stated a couple of times here that the source you refer to does not contradict the findings in the others.

Remember if you keep stating that black is white you will eventually be killed on a zebra crossing (with apologies to Douglas Adams).

 

[Edward woodwood]

I think your understanding of Mr Sutherland et als findings is 'out of context' Mr M.

 

[Nightranger]

Later on I quoted extracts from an article based on a scientific paper which appeared to contradict the opinion arrived at by most ecologists. Once again I quite deliberately expressed no opinion whatsoever on whether I agreed or disagreed with its contents but this did not stop some members behaving as though I had written the article myself - I didn't by the way!

With respect Anthony, several people have pointed out that the article does not contradict other opinions. Indeed, there is plenty of detailed discussion about why this paper is not contradictory. What is disappointing is that you have failed to even acknowledge this effort and you got into (with equal blame on both sides) a personal(ish) interchange with Jane. Other contributors have entered the thread firing rhetorical bullets that discredit any science that disagrees with their personal views. Is this a fair summing up Anthony? Equally disappointing to me personally is that I predicted the direction of the debate (as did Tim to a certain extent). Jane also proved in a rather compelling way that certain contributors only join the debate when it is a controversial subject. I just feel some people (naming no names) are operating under a disingeniously hidden agenda. Fine I suppose but it is a bit galling when a few of us put in a bit of background work to have it go completely unacknowledged or dismissed by some people. If the purpose of the thread was to stimulate a discussion on the subject then it has me wondering if there was any point given that some people find it too easy to throw away what they do not want to believe. I find that attitude mystifying and disappointing but not just from a scientific perspective but from a debate point of view.

Ian