Grey squirrels 'do not harm woodland birds in England'

[Ukwildlifeo]

Originally Posted by aeshna5

Agree it's a superb book, though Peter Marren gave a rather sniffy review of it in British Wildlife, which I found rather petty.

Really!? Well my copy of british wildlife is still in the sealed packet because Ive been too busy reading the book - hows that for a glorious bit of irony

[SheffieldLass]

Originally Posted by loripo

I think the sparrows went when all the rebuilding work was being done in towns during the sixties/seventies. We now have two or three small flocks using the now mature shrubbery in peoples gardens and around the green spaces. Here the trees aren't usually large enough for squirrels to nest, they stay in the large plane trees that were left in situ and visit places where they get fed!

In Sheffield where I used to live the house sparrows disappeared when the privet hedges that used to be everywhere between gardens were taken out. Gardens that retained their hedges continued to have them. And we all had grey squirrels.

[Dogs]

Originally Posted by tufftie

I agree about not going there again! However it's hard when something new comes up, like this, not to get the old t-shirt back out..if only to check the moths haven't munched on it!

However, there was that paper that Brains sent me about the effects of culling on various species which showed that when culled some species maintain their numbers, others suffer losses while others over compensate for it. In the case of most rodents they over compensate for the decline in numbers due to culling. This makes culling them seem pointless - unless you put up a buffer zone around a small area but then how do you maintain the reds in said area as a viable population? I've often wondered if that's some of the reason why reds are so susceptible to disease - because they are living in communities that are not large enough to maintain healthy populations? Then there's population dynamics and the only species that seems able to go against those laws and survive is humans!

Jenny the main adverse effects in nature are mostly due to humans and global warming/cooling - whether human induced or not. Once one thing changes in an ecosystem it has a positive or negative knock on effect, whatever the cause. However like Eeyore I'm not really wanting to go back over this one (my t-shirt appears to be largely free of moth holes!) - however if you look back over my old debate you will see my thoughts and research on it

I was going to stay on the topic of bird predation, but feel that I need to add my penny's worth in this debate....
Im currently working around some of the largest red squirrel reserves in the country. These are mainly pine forrest and comercial plantations, where the red's can thrive. The grey squirrel is a squirrel of broadleaved woodland, though can survive in mixed plantations. It is absolutely essential that the grey's are kept out of these areas, or we may loose our native red's completely.
In my area, the grey is a new species, and we have recently seen them take over from the red's in most of our broadleaved woodlands. This is unavoidable, and it would be foolish to think we can reverse this invasion. Ive since been inundated with calls from both domestic and landowner customers, who are suffering damage caused by the grey squirrel. However, I never once recieved a call about a problem red squirrel, and thats not because people turn a blind eye to them, or that they are a protected species, but simply because they rarely cause any notable damage of any form.
Greys are a much more serious pest than the reds ever were, and as such should be controlled in all areas to maintain low level populations, resulting in less damage occuring. And if undertaken in a profesional manner (it takes some considerable work), a healthy balance CAN be achieved... Surely, this is what any sensible woodland owner is aiming for?

[Dogs]

Squirrels, among other rodents, dont 'respond' to the actual culling itself - by breeding more profusely - but instead the 'response' comes from the fact that a void has been created, and extra food sources can be exploited.
Like rats,(if left to their own devices) they will overpopulate an area, strip their own food supplies down to the bone, before a notable decline in numbers can be seen. Resulting in a vastly depleated ecosystem, thus having negative knock on effects on a huge variety of other life forms in the woodland ecosystem.

[Paul mabbott]

This isn't actually new data. The paper quoted is a metanalysis of previously available data. I (like most everybody here, I imagine) have read only the summary on the BBC site or elsewhere. Even on that reading the use of the headline "Grey squirrels 'don't harm birds'." is a patent nonsense.
The summary says there is no evidence that most common species are unaffected by grey squirrel activity but some species may be and there is no evidence either way regarding rare species. It is, however, the latter that are critical - a species which is rare may be made locally extinct by predation or competition!
I shall be interested to read the paper.

Originally Posted by tufftie

I agree about not going there again! However it's hard when something new comes up, like this, not to get the old t-shirt back out..if only to check the moths haven't munched on it!

[RKB]

Originally Posted by tufftie

The long and short of this is that squirrels, be they grey or red only take birds eggs when they are running out of other food sources in their area

What kind of staple food source would a squirrel be running out of in May? Plenty of vegetation and a glut of insects (caterpillars).

From my experience squirrels predate nests opportunistically, and I have seen them predating tit nests in live mature trees by knawing open the holes - it must have taken them hours! But in mys studies this is a very low rate of predation - much less than weasels, woodpeckers and even rain.

It's worth saying that the paper shows only correlations, not causes. So if squirrel numbers are associated with lower populations of bird x, that just tells you that there is a relationship, not a cause. This is the problem with meta-analyses - it flags up relationships but not what those relationships are. There might be different factor(s) that are influencing bird and squirrels numbers in opposite ways, without them affecting each other.

For instance, squirrel numbers were positively associated with some bird species in the paper, which was attributed to habitat being good for both. Nobody is suggesting that squirrel numbers promote e.g. Coal Tits. This logic means that (quite reasonably) the opposite is also true - there can be a negative relationship with bird numbers without the squirrels causing it - it may be habitat nuances again. So the paper is basically a tool to flag up areas for more detailed work. Previous studies have failed to conclusively pin squirrel predation to any bird decline.

It's also worth noting that greys don't do anything that reds don't do, re bird predation, but that isn't necessarily important because bird densities are different and so, therefore, is the potential pressure and impact. People/foresters considered reds enough of a pest to have bounties on them into the 20th century.

One impact of greys rarely mentioned is their impact on hazel. By taking virtually the whole national crop before it matures, they have arrested the ability of hazel to naturally reproduce. Hazel is now totally reliant on people to survive. Apparently, reds took hazel nuts at a later stage and allowed some to be be sown.

Finally, re introduction vs native. Reds went virtually extinct in Britain in the 18-19th Century and were widely reintroduced from Europe. They are unlikely to be the same race as was native, and so can themselves be considered an introduction.

[mbaldw]

Hi RKB,

thanks for a very informative and interesting response. I have a quick query regarding one part:

One impact of greys rarely mentioned is their impact on hazel. By taking virtually the whole national crop before it matures, they have arrested the ability of hazel to naturally reproduce. Hazel is now totally reliant on people to survive. Apparently, reds took hazel nuts at a later stage and allowed some to be be sown.

Do you have any other details of this phemomenon (some of the studies, perhaps)? I know that greys have been implicated in various forestry problems, but I wasn't aware they were 'big players' in hazel decline. In their paper to Biological Conservation last year Sheffield Uni biologists Javier Laborde and Ken Thompson wrote:

"Indeed, American grey squirrels - which are both bolder and less exclusively arboreal than the native red squirrel (S. vulgaris ... ) – may well be more effective dispersers of Corylus into open grassland than red squirrels. It may be no coincidence that Corylus has spread markedly in Cressbrook Dale over the last 40 years, a period that has seen the replacement of reds by greys across central England."

They concluded that grey squirrels were the most important dispersers of hazel into grassland, but perhaps this is insufficient to offset any arresting of hazel woodland regeneration?

Cheers,
Marc.

[RKB]

Originally Posted by mbaldw

Hi RKB,

thanks for a very informative and interesting response. I have a quick query regarding one part:

Oliver Rackham makes a big deal of it in his NN 'Woodlands' book. I haven't seen any studies (it's slightly out of my lit) and took it at face value. It does mirror my experience, however, as I don't think I've ever seen a hazel bush attain more than a couple of mature nuts as the squirrels strip them well before they're mature, and I have never seen a natural hazel sapling. Granted though, my statement probably needs more backing than that (depends whether you trust Rackham or not!).

Hmmmn, but if Laborde & Thompson have documented hazel spreading over Cresssbrook Dale....maybe Rackham's being a bit rash?

Rackham (Woodlands, p.356): "Hazel has fared badly. Grey Squirrels have taken away its means of reproduction. Usually all the nuts have disappeared by August while still reen and unviable, and a young hazel is a rarity. Hazel is thus a threatened species, although its longevity will see it through some centuries to come".

[mbaldw]

Thanks for that, I'll take a look at Rackham's book.

Hmmmn, but if Laborde & Thompson have documented hazel spreading over Cresssbrook Dale....maybe Rackham's being a bit rash?

Maybe this is a more recent development, given that Rackham's book was published a couple of years before the paper. I notice that there's a new edition of Rackham's book due to be published in March; it'll be interesting to compare that to the original.

Cheers,
Marc.

[danthekeeper]

I am surprised at the last few posts re hazel every year we gather hazel nuts by the bucket and my friends love them perhaps we have more hazel than the squirrel's can cope with.That said we don't have that many squirrel's even though we have never culled them