I did say that the Game Fair might keep this blog going for ages!
In one of his very amusing and entertaining, though not convincing, rants, Robin Page voiced the views that Songbird Survival was a very good organisation and that it was obvious that sparrowhawks and other predators were part of the reason for songbird declines.
I picked up some literature from Songbird Survival at the Game Fair and see that they claim to be ‘Saving songbirds with science’.
Songbird Survival did indeed fund a repeat analysis of the massive BTO database on population numbers of songbirds (and other birds) which includes the results collected in the Common Birds Census period and that collected more recently under the Breeding Bird Survey.
The Songbird Survival funded study was published last year and looked at several species of predator (eg grey squirrel, carrion crow, magpie and sparrowhawk) and a whole range of songbird species (eg both sparrows, several buntings, warblers, tits and others).
That study provided no succour for the view that is widely held, and not, on the face of it at all foolish, that such predators might affect the population levels of their prey. So they might. There are quite a few ecological reasons why they might not, but they might. But the analysis of the data – and it is an enormous dataset – did not suggest that sparrowhawks, magpies etc were responsible for the widespread declines of species such as skylark, song thrush or bullfinch (or many others). The summary (and if you look further – the whole paper) of the paper is available here online.
The research was carried out by BTO, St Andrew’s University and the Game and Wildlife Conservation Trust scientists. Here is how I described the study in a previous life and that still looks a pretty fair assessment to me.
This study is sometimes described as inconclusive but that is only true in the sense that any unsuccessful search for something finds it difficult to be absolutely definitive that it isn’t there. The evidence for the lack of little green men from outer space turning up on earth is inconclusive – we may have looked in the wrong places, at the wrong times and in the wrong ways – but it is probably pretty safe to base your life on the expectation that they aren’t there until the evidence changes.
But that doesn’t suit Songbird Survival whose literature still (as of the Game Fair on Saturday anyway) pictures a lot of predators, including magpies and sparrowhawks, and says ‘These predators are badly damaging our songbird populations’. That’s not what the latest science says is it? Songbird Survival doesn’t seem to be able to take on board the science which they themselves funded, and on which they are completely briefed and well aware.
Songbird Survival probably rates an entry in my occasional series on the raptor haters – but we’ll leave it for a while before going there.
[registration_form]
Songbird Surviaval and all that – How about the ongoing Avon Valley Lapwing work as an example of possible predation limiting a declining species? Perhaps a comment on Loddington as well?
Birdseye – I missed you at the Game Fair – were you there? Very keen to comment on Loddington – particularly in the context of the comparison with the RSPB’s Hope Farm. It wouldn’t be that the GWCT are dragging their feet on this joint paper would it?
By coincidence I was at Loddington only yesterday and mentioned this collaborative paper; GWCT are certainly not dragging their feet, altho’ I know that the Trust’s biometrics expert has much else on his plate at the moment. I agree it will be a fascinating piece of work. Mind you, there is an element of apples and oranges about it, as I understand there is a marked difference in the nature of the habitat (Hope Farm much more open?), and you have conceded previously in another place that the predation pressure at Hope Farm is significantly lower than at Loddington.
Sad to miss you at the Game Fair, but I enjoyed meeting your successor, with whom you won’t be surprised to hear I have already been in contact about Lake Vyrnwy…
Lazywell – welcome! I’m attracting quite a clutch of GWCT supporters here – which I like, of course. I’m sorry to have missed you at the Game Fair but I’m glad you met my excellent successor – I must brief him about you. I do hope that GWCT isn’t dragging its feet as they were very insistent on doing a comparison between Loddington and Hope Farm to which i was very happy to agree (in a previous life). You are right to say that there are differences between the two sites but both are, without doubt, success stories of integrating wildlife conservation with productive farming. So let’s see the data soon please.
I will relay your keen interest to the powers that be. The results were certainly rather surprising at first blush, but you can be sure there is no sense of guardedness about publishing them; nor giving full credit where it is due.
Oh, and worry not – Martin has already been well briefed about me by your erstwhile Scottish colleague.
Like the Norwegian guy who just killed all those kids he still wants the publicity so the best way to deal with this group of morons is to stop writing about them as you are only advertising their presence.
John – first, please keep the comments challenging but polite, please. I think the analogy between SS and Anders Breivik is a bit weak – but if there is something to be learned it might be that good people should speak up for what they want rather than assume that those with more extreme views will simply go away? And SS has some quite powerful friends so they may not go away.
A one farm example, for or against the hypothesis, is not evidence of a mechanism at the sacle of the population which is what the BTO analysis, using correlation was trying to achieve. And while the dataset could be described as large and the best there is it is not by any means perfect for such analyses. Finally, what annoys me most, about all of you, is the fight to try to see one headline triumphing over the other when it will certainly be found that predators have proportionally higher effects on species that are declining for other reasons.
Tom, I am sure research will show predators have a proportionally higher effect on species that are declining for other reasons. That is a very strong argument for reducing the other reasons so that predator and prey can exist together. It is certainly not an argument for reducing the predators whilst failing to deal with the fundamental underlying reasons of species decline.
Bob – well said!
Tom – welcome to this blog! You are right that a one-farm example will be an interesting insight rather than ‘proof’ of a general truth. And you are right that no dataset is perfect (a point I have made about the BTO, University of St Andrews and Game and Wildlife Conservation Trust analysis before – follow the links in this blog). But there aren’t many organisations who would commission research and then apparently ignore its general findings in their literature. SS claim to be ‘saving songbirds with science’ yet there is precious little evidence of them saving songbirds nor of them taking much noticve of science.
I’m sure I’d find the answer reports… but to save time can you tell me if Songbird Survival has a mission, i.e. to kill predators or to save species, or both, and if it’s to save, which species? Gamebirds first is it?
Nige – welcome to this blog! SS is supported by prominent members of the game-shooting community but says that it is interested in saving songbirds so we must take them at their word (shouldn’t we?). Their chosen methods of helping songbirds seem almost always to involve slagging off predators – even when the research they fund suggests that predators play rather a small role in songbird declines.
If you have higher population levels of nest and young bird predators then you are going to have higher levels of predation on nests and young birds which must lead to a decrease in the populations of the predated species . This is not rocket science it is basic common sense!
If the population data used does not contain researched mortality causes then no way is there going to be a link between populations of predators and populations of their prey species.
I think Mark that you will find that the results show that there is no evidence to show a link between predator numbers and prey species (songbirds) numbers and NOT that the results show that predators do not have an effect on songbirds as you suggest in your blog. You cannot come to any certain conclusion from a lack of the correct type of evidence. Maybe you are a little biased here as well
Dave H – welcome to this blog. So, on that basis, any mortality would cause a decline in population numbers? So all wildfowling should be banned as it must cause population declines? I think not. i doubt whether you believe that and I know that I don’t. Life is not all common sense otherwise you wouldn’t need science and the earth would indeed still be regarded as flat!
You are right to say that the study in question does not prove that there is no effect of predators on their prey – i think that’s what i address in the paragraph that mentions little green men. i can’t find the paragraph where I say, what you say I said, that it shows that predators don’t have an effect. However, that is what it strongly suggests.
Your middle paragraph does not make sense. I think you misunderstand the study.
I gave the link to the original study and i don’t think you’ll find my description of it inaccurate – so i don’t know why you accuse me of bias.
OK – Let’s accept for the sake of balance in this blog that predators have an effect, but that there are other management matters [MM] that would help songbirds. Let us also accept that we should deal with the other MM before predators.
What are the other things we can do? Skylark plots [as Grange Farm] – please annotate the remainder and against each one which bird is helped. In addition, spell out, why it is not happening at the moment – blaming subsidy is not enough, unless clearly disadvantaging one or more MMs. Furthermore let us accept that some of us who comment here have practical experience from over 40 years and maybe to disregard that experience just because it is not science or research findings might be deemed somewhat discourteous?
Earlier this year there were 2 or 3 articles in the Times – the first from the leading light in songbird survival – saying that more rigour was needed in researching the reason for declines especially as related to predators. None of them mentioned the study, which came before the articles. Instead they repeated the usual theories and made much or a crow/magpie (can’t recall which) culling trial to be conducted in the west country. One could easily form the impression that, having got the ‘wrong’ result the first time, that someone was trying again until the Sparrowhawk came back into the frame. I have also on occasion been less than impressed by the trust’s newsletter – of course articles in a newsletter are often more about background and colour than strict fact – but a piece on how the skies of the Chilterns were dark with raptors to the exclusion of songbirds did not at all chime with my experience.
I think that when there are issues of natural science, then if the theory and evidence put forward are nonsense, then it must be rigorously, firmly, frequently and publically refuted, especially by anyone in any public natural history role….
Regarding your view about predators i agree i was probably reading between the lines. wildfowl and pheasants etc have evolved to cope with hunting pressures and have large clutch sizes of perhaps 14 eggs/young so this is not a fair analogy. Another disputed point I made which i will try to clarify is that if causes of mortality are not monitored and recorded then the effects of predators on prey species cannot be analysed with accuracy. Normally an increase in prey species will lead to an increase in predator numbers. It is not so much the numbers of predators /prey present but the timing of their ratios of abundandance which is important
Ed – welcome to this blog.
So lets accept that predators eat song birds, simple we all know it happens. They have been doing it for millenia, in fact for far longer than we humans have been controlling predator numbers. Yet until very recently there were no catastrophic declines of song birds, predators uncontrolled did not eliminate them. Indeed had they done so most of the predators would themselves have died of starvation. So we need to understand why this mechanism works. Song birds always rear ( as a population) more young than they need to so that taking mortality into account there will be roughly the same numbers of breeders next season. So if in August there are 6 Blue tits where there was before breeding 2 then as long as there are two left to breed next year thats OK. It works for all species incidentally, so if the local sparrowhawk eats no more than four before they breed it matters not or if they are red grouse it matters not that four or less are shot. When I was a student there was a wonderful book explaining all this in easy to understand terms not jargon called “Why big fierce animals are rare” by Paul Colinvaux.
What SS people do if they are not game people hiding is ignore the environmental changes we have made which cause bird declines by increasing mortality and blame the easy option, the predators, its rather akin to racism in times of high unemployment. Blame the easy option not the right option, we don’t like thinking, even collectively its our fault.
Some game shooters just don’t like sharing the breeding season surplus with anything else, its called greed I think. Hence their calls for predator control. They want the balance tipped in their favour and not to let nature manage it for them.
Paul
No one seems to want to enumerate the reasons for the declines? Contributors seem to want to argue with those who have pointed a finger at raptors? Surely we would all be happy if there healthy populations of songbirds and raptors. I am baffled by the continuing assertion that Songbird Survival is somethng to do with biased shooters – a little evidence maybe, science based?
Birdseye, surely the very evident expansion of our human habitat, (houses, roads, airports, shopping centres, etc), is an obvious cause of habitat loss which deprives many species, songbirds and all the others too, of both food and somewhere to live. Also, the need of our ever expanding population for food, which puts pressure on agriculture to intensify, is also a clear reason for declining fortunes of songbirds who no doubt would benefit from more “weeds” , hedges, undrained wetlands and native woodlands.
To push raptors and other predators to the front of the queue when picking reasons for the decline in bird numbers is blinkered and somewhat ignorant of a rather obvious truth. We are the problem and unless we work towards understanding our impact and controlling our behaviour then we and the birds are all buggered!
Does that go some way towards enumerating the reasons for the declines?
Chris – welcome to this blog!
Paul – that is an excellent book and well worth reading by anyone who wants to understand the relationship between predator and prey in layman’s terms.
If you think that a Sparrowhawk only has about a 30% chance of catching its prey every time it sets off on one of its sorties you begin to understand that a Sparrowhawk in your garden is there because of the high numbers of birds in it. And it’s the same for every predator – it’s basic ecology and I don’t understand why organisations like SS don’t seem to grasp this. Sure, where there is a particularly rare species of songbird or other species present they can be put under additional pressure by predators and some control may be appropriate, but it’s always the last resort and after proper assessments. Song birds – Passerines – as we should probably more accurately describe them are under far more pressure due to agricultural intensification, the hard landscaping of gardens, general obsessive tidying of the countryside and a whole host of other issues, including and, probably most worrying, the effects of climate change in this country and on wintering grounds abroad. Predators are the least of their problems.
When my rabbit population was out of control, there was a multiplicity of buzzards. Now that the rabbit population has been cut back, there are fewer buzzards. We always have an abundance of sparrows, swallows, swifts, house martins and this year a number of feral pigeons have joined the Carbeth family. THE sparrow hawk makes its presence felt each year. I hate it because it often kills blatantly right in front of me, but there is clearly enough being raised to keep it going without impacting on numbers. I have however, noticed an absence of blackbirds and song thrushes though, and sawTHE sparrow hawk attacking a blackbird before being mobbed by the swallows. I’m just hoping my peacock chicks are now too big for it.
it is irrational how people dislike predators especially sparrowhawks, but have no problems with robins killing worms, dolphins devouring fish, whales wolfing down krill or ladybirds chomping aphidsì. Some of those who express such extreme emotions may also be meat eaters themselves and not only have the privilege of eating meat without having to face possible death by starvation if their hunting skills are not up to scratch, but are surely aware of the brutality and cruelty involved in the rearing and butchering of cattle pigs and chickens.
Animals kill others to survive, while we do it to titillate our tastebuds often unconcerned iabout the huge environmental damage our collective habit causes.
Daye,
surely hate is too strong a word, although I accept you do not like it, after all the sparrowhawk is only doing what nature designed it for and knows no better. I too have a regular who visits my very urban garden which also remains except during those brief visits full of blackbirds and sparrows with the odd thrush most days, I am filled with wonder by all of them including the hawk, who of all of them really lives at the cutting edge of survival.