Surely chopping down trees can’t be good for nature?

It’s counter-intuitive, chopping down healthy trees in the name of woodland conservation. Walking around the woods, and stumbling across a new clearing surrounded by 6ft high-visibility plastic fencing doesn’t exactly give you a glow of seeing nature at its best. So I can understand why the grumpy dog-walker was so upset by the work the Wildlife Trust had done in one of the woods I regularly visit. But despite appearances, this work is vital for the wildlife that lives in the wood.

While we think of our woodlands as wild places, humans have played a big role in making them what they are. When the need for wood as fuel, or for ship-building, was greater, many of our woodlands would have been managed in some way, for example coppicing. Coppicing is where every few years trees and shrubs are cut down to ground level, to allow vigorous regrowth. Coppicing can help trees live longer, and crucially allow light into woodlands.

Without management of some kind our woods would soon go from beautiful wildlife havens filled with birdsong and bluebells in spring, to deep, dark, silent places reminiscent of troubling fairy tales. When trees grow too big, they prevent light reaching the understory (lower-growing plants), so these plants disappear, along with the insects, birds and animals that depend on them for food (like the dormouse).

So that explains why the trees were cut down. But why the ugly fencing? The fencing is needed to keep deer and bunnies out. Deer have a voracious appetite, and would quickly eat the new shoots coming from the coppiced trees, preventing them from re-growing properly. Once the coppiced trees are big enough, the fences can come down to let everything wander freely through the coppiced area.

So chopping down some trees (done not too much, nor to frequently) can help to ensure our woods remain how we like to think of them, bursting with life of many kinds. While the work might not be pretty in the short term, it’s essential.

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Alien invaders 1: Canada Geese

Canada GeeseEach day I walk through the park, past the mill pond, and nod good morning to one particular goose. He’s quite distinctive, with the white marks on his face. He’s the patriarch of the community of Canada Geese on the mill pond. While his many goslings are growing up, he tirelessly watches over them, protecting them. (Unlike the ducks, which take a rather more laissez faire approach to parenting, letting their tiny ducklings zoom off or get left behind.)

Over the years I’ve grown affectionate towards him – you’ve got to admire that kind of devotion. A couple of years ago a tree fell right on top of the nest his mate was sitting on, yet miraculously she and the eggs survived, and together they brought up the large brood. I was rooting them on, each morning anxiously counting the number of goslings to make sure they were still surviving.

Goslings

So it came as more of a surprise to me than it should have, when I learned that they count as an invasive non-native species. I mean, the clue’s in their name: Canada Geese. But I still find it hard to think of them in the same category as Japanese knotweed. According to the GB Non-native species secretariat, an invasive non-native species is any non-native animal or plant that has the ability to spread causing damage to the environment, the economy, our health and the way we live.

So, are Canada Geese a problem? They’ve lived in the UK since they were first brought from North America to St James Park back in the 17th century. But their numbers have increased hugely over the last 60 years, going from 4000 in 1953 to around 89,000 in 2000. They are viewed by many as pests – they make a lot of mess on footpaths in parks, and there are concerns they may spread salmonella to cattle. Canada Geese who are nesting or looking after young can be aggressive towards people (which can be a problem as they seem to like living in public parks, bringing them into close contact with people, particularly children). Their droppings may increase the nutrient content of water, which reduces oxygen content for fish. And around airports there have been problems with damage to planes and people when they collide with Canada Geese. The main issue is they are so numerous…

In fact, in some places the eggs of Canada Geese are treated so they will not hatch, to try and prevent them from expanding even more. So while I was rooting on each of the goslings, should have been hoping the reverse? I try and be fairly unsentimental about my love for wildlife. But I can’t yet find it in my heart to feel anything other than affection for at least this one particular Canada Goose, alien invader though he may be.

The badger cull: an ‘evidence to policy’ perspective

Lots has already been written about the badger cull. There’s no dearth of emotive responses to it online. If you’ve visited my blog before, you’ll probably have picked up that I love wildlife. What you may not know is that, in my day job, I work on randomised controlled trials. More specifically, I work on translating the evidence we get from trials into policy and practice. So I’m trying to write this post with my ‘evidence to policy’ hat on.

Randomised controlled trials are the most reliable way of finding out if an intervention works. This short film explains why randomised controlled trials are important.

Outside of medicine, it’s rare for proper randomised controlled trials to be conducted to test if an intervention works. So the fact that a trial was conducted to test whether badger culling reduces bovine TB is a big deal. It means we have high quality evidence about the efficacy of badger culling.

So what did the Randomised Badger Cull Trial (RBCT) find?
The trial found that after 4 years of culling, bovine TB in cattle was reduced by 23% in the cull areas, but increased by 25% on the land less than 2km from the cull zone. It also found that localised reactive culls (where badgers are culled only after an outbreak of bovine TB) actually increased bovine TB in cattle.

Does this mean the current badger cull will help reduce bovine TB?
While it might initially seem that the evidence from the trial supports the current cull, it’s actually much more complicated. When working out whether the results are generalisable, (will apply in a different setting to the original research) we need to consider whether the intervention being used now is the same as that used in the trial.

In the RBCT badgers were culled by being trapped in cages then shot. This method is expensive, but it reduces the chances of badgers being missed, or being wounded and then escaping. The current cull is looking at free shooting, which hasn’t been trialled, and might not be so effective at killing badgers.

The proportion of badgers that are culled within an area is also important. In the trial, 70% of badgers in cull areas were killed. If the proportion killed is lower, it doesn’t simply mean there will be less reduction in bovine TB. This is because culling causes badgers to scatter further afield than they would otherwise (this is called perturbation), which, if they are infected with TB may actually result in increased transmission to cattle (as was found in the reactive cull areas, and those around the cull zone).

That’s why the pilot culls are important: we need to know whether free shooting is effective at killing enough badgers to make it likely that there may be a reduction in TB in cattle. Both pilot sites (Somerset and Gloucestershire) have been unable to kill the required proportion of badgers, and extensions to the cull periods have been applied for. The pilots have proven that free shooting cannot kill enough badgers quickly enough. This raises the risk that the culls may actually increase perturbation and therefore bovine TB.

What else needs to be considered when thinking about translating trial evidence into policy?

Cost-effectiveness RBCT found it wasn’t cost-effective. That’s why in the current cull they decided to go for free shooting rather than the more expensive trap and shoot used in the trial. The calculations were that it might be cost effective with this cheaper method. However, with the costs of policing the pilot estimated to run into millions, this now lookes unlikely. This is exacerbated by the apparent failure of free shooting to kill enough badgers. Failing to reach the target proportion of badgers culled increases the risk of the cull causing perturbance, which could increase bovine TB. To tackle this, there are reports that hundreds of cages have been brought in. This will increase the costs of the cull, and may well mean any benefits are outweighed by the monetary costs.

Feasibility: as well as considering whether an intervention is effective and cost-effective, policymakers need to consider whether it is feasible to implement it at the required scale and quality. The necessity of extending the length of the pilot culls would perhaps indicate that it is less feasible than anticipated.

Acceptability: clearly, given the keeness of the NFU to introduce badger culls, the intervention is acceptable to many farmers. It is equally clear that the measure is unacceptable to many in the general public, as evidenced by the number of signatures on petitions against the cull, and active protests around the country. It doesn’t look like a compromise is likely to be possible.

Need: bovine TB is a major problem, costing the UK £90m last year. Farmers and DEFRA argue that this means something must be done. However, it doesn’t make sense to argue that because something must be done we must do something that is likely to be ineffective (and probably harmful to the cattle who we are aiming to protect), and where the monetary benefits are outweighed by the monetary costs. We need to find ways to tackle bovine TB, but that doesn’t mean we should ignore the evidence on the likelihood of effectiveness and costs of any strategy.

Risk: a first principle of medical interventions is ‘first, do no harm’. The scientists who carried out the RBCT have come out strongly against the cull, saying it is not supported by the evidence, and is more likely to do harm to cattle than good.
Wiping out large numbers of badgers is likely to have effects on other animal species as well. We have to be careful when messing with the natural foodchain, as changes in the numbers of one species affect many other species. Reduced competition from badgers may well lead to an increase in other species, such as foxes, who aren’t too popular with many farmers either.

Ethics: badgers are protected by law. They are living creatures. One of the aims of the pilot cull was to assess the humaneness of free shooting as a method of killing badgers. It has now been admitted that it is unlikely to be able to tell us this. There is even talk of gassing of badgers in their sets, despite this having been outlawed 3 decades ago for being inhumane.

If we, as a society, are consciously going to wipe out large numbers of any of our native species, we need to be very sure it will have the effect we want. I believe the current evidence does not stack up. The cull is unlikely to significantly lower incidence of bovine TB, may actually increase it, and will cost more than the benefits are worth. We need to tackle bovine TB, but this is not the way.

Only connect: children and nature

This week the RSPB launched a report about children’s connection with nature. This looked at empathy for creatures, having a sense of oneness with nature, having a sense of responsibility for the environment and enjoyment of nature. According to a survey of 1,200 children from the UK, conducted as part of the research, only one in five children had a good connection to nature. If you would like to see how connected you are with nature, you can take the survey here.

Being connected with nature is important for all of us. Previous work done by the RSPB has suggested that spending time in nature is good for us both mentally and physically. But it’s also really important that children have a good connection with nature, as if they don’t value it then they are not going to look after it when they are older.

Reading about this report made me think back to my own childhood, and try and work out why I became interested in nature. I can’t think of a damascene experience, but a few early memories do stand out.

Frogs and slow worms
I remember spending lots of time playing in the garden when I was young, chasing frogs and finding slow worms. I was surprised a few years ago, when Fat Cat brought in a frog, how hesitant I was about picking it up. I certainly had none of that squeamishness when I was a child!

Acorn treasure
The infant school I went to used the park as a playground. There were some magnificent oaks in the park, and I remember each year gathering acorns as treasure. Green ones still in their cups were the ones I prized most. All these years later the sight of an oak tree laden with acorns still thrills me, and I often can’t resist gathering a few acorns.

Wildlife Watch
When I was a bit older my mother’s godmother bought me membership of Wildlife Watch (the Wildlife Trusts’ club for children). I remember a brilliant weekend on Dartmoor, learning to identify antiseptic moss, dambusting, visiting a badger rehabilitation centre, and going for a midnight walk on the moors.

Reading animal stories

I was always an avid reader, and I think the animal stories I read as a child played an important part in getting me interested in wildlife. I’m sure some experts look down on anthropomorphicised animals in children’s books, but I think beautiful stories like the Brambly Hedge books, Wind in the Willows, and later the Animals of Farthing Woods and Duncton Woods can help children learn to love wildlife and nature.

Nature is fascinating and beautiful and disgusting enough to capture the imagination of any child, given a chance. I’m determined to help my god daughter and nephew to grow up connected to nature. I want to give them a chance to experience the wonder and joy of exploring our natural world. I’m not sure where to start, but I have a few ideas.

Were you connected to nature as a child? What got you interested in wildlife?

Bird nerd part 2: summary stats

So, having collected all this lovely data, what do I know about the birds that visit my garden? Here are some summary stats from the last three years of data collection.

  • In 2010-11 I saw on average 7 different species per observation day. In 2011-12 this went down to 6, and in 2012-13 it went up to 8.
  • In 2010-11 I saw on average 14 individual birds per observation day. In 2011-12 that went down to 12, and in 2012-13 it went up to 15.
  • These averages hide quite a bit of seasonal variation: September is generally pretty quiet, while the bird table is unsurprisingly busy in December and January.
  • The most regular avian visitors to the garden were: bluetits in 2010-11, being seen on 55 out of 64 observation days, starlings in 2011-12, being seen on 35 out of 43 observation days, and woodpigeons in 2012-13, with only one observation day out of 44 when they didn’t make an appearance.
  • The most numerous visitors to the garden were starlings by far (which won’t surprise anyone who has seen hoardes of them descend on a bird table), although in the last year house sparrows have almost managed to catch them up.

    Bluetit
    Bluetit gathering nesting material

Changes in which species visit over time

As I mentioned in the first ‘Bird nerd’ post, altogether I’ve seen 26 different species of bird in the garden, although never all in the same year. In 2010-11 I saw blackcaps on 15 observation days (in the winter), but only once in 2011-12 and once in August 2012-13 (which is a shame, as they are pretty birds).

There have been no records of jays since 2010-11, but even then they were not frequent visitors. Other birds missing in 2012-13 that I have seen (infrequently) in other years include crows, greenfinches and siskins.

On the bright side, in 2012-13 I saw chaffinches and some kind of warbler for the first time. It’s quite encouraging that 4 years after moving here we’re still spotting new species.

Future analysis to be done

The few stats I’ve presented here are only the tip of the iceberg in terms of what I could examine from my data. One question I would like to look at is how the weather affects bird numbers. I’ve got very basic data on weather for most observation days, but only as far as whether it was sunny, snowy, rainy or overcast. Since we had solar panels installed last June I now have data on sunlight. My theory is we get more bird visits on sunny days than rainy or overcast (controlling for the month of the year), but we’ll see if the data supports that…

Let me know if there are any other questions you would like me to look at – for example, if you’re interested in a particular species or comparison over time…

Whose pawprints are these?

I’ve got an exciting new toy! It’s not much to look at. A black plastic tunnel. But it’s great at creating suspense. It’s a tool for finding out which small mammals visit your garden, by capturing their pawprints.

It’s very simple. You put the tunnel along a fence or other boundary in your garden. You put some bait in the middle of the removable black plastic plate, paperclip a piece of paper at either end, and put a strip of special safe ink either side of the bait. The animal has to walk through the ink to get the bait, and on their way out leaves inky pawprints on the paper.

We tried it out baited with mealworms (I’ve yet to discover an animal that doesn’t love the disgusting looking things). The ink is a mixture of black poster paint and vegetable oil, so is safe for animals to lick off their paws.

Here are our results from the first night of monitoring.

Hedgehog and mouse pawprints
Pawprints from the mammal tunnel

There are definitely hedgehog prints, but I found it quite hard to tell from the diagram what the smaller prints were, so for the second night I decided to add an infrared camera to the tunnel, which together with motion trigger software showed us this: (nb. this is a speeded up version which only includes when the animals are actually in the tunnel).

Mystery solved: mouse and hedgehog.
Not really a huge surprise, as we knew we had both in our garden. But it’s fun to get their pawprints and film them. On a more practical note, if you didn’t know what visited your garden, this could be a good way of finding out. And more importantly, you can submit your results to the National Mammal Atlas Project.

You can get the tunnels from the Mammal Society, and submit your results there too (nb. They don’t come with infrared cameras – that was my own modification).

Amateur ecology

Over the last few years I’ve been doing quite a lot of reading about wildlife, as well as going on courses. One of the biggest surprises I’ve had is there’s so much we don’t know, even about some of our most familiar species. For example, we don’t really know what water voles do all winter, or where basking sharks go. Linked to the realisation of how much we don’t know about our wildlife, is the discovery that normal people, like you and me, can make a meaningful contribution to scientific research about wildlife.

The other day I read, in Hugh Warwick’s book The Beauty in the Beast, about Denis Summers-Smith. It was inspirational. Denis is a mechanical engineer and an amateur birdwatcher, who has written five books and over forty scientific papers on the house sparrow. He has discovered many things about house sparrows, including that they mate for life. And all this has been done in his spare time…

For those of us not quite ready to write a book based on our own discoveries, there are many citizen science projects that rely on the contributions of hundreds (or thousands) of volunteers to gather data from across the country. The commitment and expertise involved varies considerably.

For example, each year in January the RSPB run the Big Garden Birdwatch. Almost 590,000 people took part in it in 2013. This involves spending an hour counting the different types of birds that come into your garden on a specific weekend. From this, they can analyse the data from across the country, and spot any significant changes in the bird population. This is important to inform conservation work.

Many other organisations run similar surveys. This BBC Nature article contains a good list.

At the other end of the spectrum, the National Dormouse Monitoring Programme is rather more indepth, requiring trained and licensed volunteers to carry out box checks each month (except over winter). The data collected from this programme is providing new insights into these lovely creatures. At a dormouse conference I attended a couple of years ago, it was very exciting to hear scientific presentations based on data that I helped (in a very small way) to collect. We now know much more about this species than we did before the programme started.

Like many girls of my generation, I gave up studying science after I finished my GCSEs, despite getting my best grades in science and maths. I didn’t think science was for me. I didn’t realise how exciting science could be, and the range of things it could involve. It has been thrilling to learn, somewhat belatedly, that science is for me, and I can contribute to finding answers to questions about our native wildlife. These answers may help us better protect our beautiful and vulnerable creatures, for this generation and those to come.

Hog watching

The first we knew about our nocturnal visitor was when my infrared motion-triggered camera caught the unmistakeable shape of a hedgehog snuffling on our lawn. We were very excited, having not seen one for years. So, in an effort to encourage it, each night we would put out a bowl of mealworms. The camera was getting regular footage of the hedgehog, and the bowl was emptied each night. Then, as summer progressed and the days got shorter, we would sometimes see the hedgehog munching away, oblivious to the light and us watching through the French window.

Hedgehog eating mealworms
Hedgehog eating mealworms

I wanted to find out more about our nocturnal visitor, so I read Pat Morris’ excellent Hedgehog book. He said that research had shown that what people think of as being ‘their’ hedgehog, a regular visitor to their garden, actually is several hedgehogs. So we decided to try the experiment he suggested. By marking our hedgehog with a small dab of paint on his (or her) spines, we would be able to tell if the one we saw the next night was the same. And he was right – the next day it was a different hedgehog munching the mealworms. So we marked that hog in a different place. By the end of that summer we had seen 7 different adult hedgehogs in our garden, much to our surprise.

We were also able to watch a hedgehog courtship (which seems to involve the male pestering the female until she gives in, temporarily distracted from the mealworms). And then 3 little hoglets started appearing with their mother.

Hedgehog and hoglets
Hedgehog and hoglets

Watching the hedgehogs over the course of the summer was a real privilege and joy. They’re surprisingly quick when they hitch up their skirt and run. They can squeeze through unfeasibly small gaps in hedges, and climb better than you’d expect. They’re not the cleverest animals. They love mealworms, but ignore the slugs that climb into their bowl. Their preferred approach to eating the food we leave out is to climb into the bowl with their food, stand on top of it and then wonder where it has all gone.

My top tips for hog watching:

  • If you don’t know if you have hedgehogs visiting your garden, look out for hedgehog droppings. Many wildlife books are a bit bashful about putting in photos of droppings, but it’s much easier to tell from a photo than and description or drawing. The Collins Complete Guide to British Animals has a good guide.
  • If you have (or can borrow) an infrared motion triggered camera, set it up so it is aimed at wherever the hedgehog is most likely to visit. In our case it was under the bird feeding station, where mealworms sometimes get dropped, and near an ants nest in our lawn.
  • If you have hedgehogs visiting, encourage them to come to a part of the garden you can easily see by putting out bowls of food (meal worms – rehydrated if you buy dried, or dog food).

House sparrow explosion

House sparrows have been fairly regular visitors to our garden. We see them all year round, with an average number of 3 per observation day. But in the last few weeks the sparrow population in our garden seems to have exploded. Before September this year, the most we’ve seen at one time was 9. Now there are more than I can count (they keep moving!).

They’ve been hanging around our garden quite a bit, and getting through the bird seed faster than I’ve ever seen before. I’ve no idea why we have had the sudden increase. In previous years there hasn’t been a large increase in numbers around this time of year.  Perhaps they’ve had a particularly good breeding year?

They’re not the most spectacular of birds, but it’s great to see so many of them, as their numbers have plummeted in recent years. In the 1970s there were around 12 million pairs in the UK. Now there are between 6-7 million pairs. The good news is, data from the British Trust for Ornithology suggests that the decline has stabilised. Now we just need to work out how to help them recover.

Earlier this year we installed a sparrow terrace (to try and tempt them away from our gutters as a nest site). The boxes weren’t used this year, but hopefully some of our new visitors will decide they’re a good nest spot for next year. I’ll let you know!

Have you noticed anything similar in your garden?