The Future of the Brown Hairstreak (Thecla betulae)

This is something of a follow up to Joe Grainger’s great blog post last year  – covering many of the reasons behind surveying for Brown Hairstreak eggs, and methodology of BH conservation efforts undertaken on many of the sites we help manage.

In regards to our conservation efforts, this year we have done much of the same – clearing (“scalloping”) areas of mature blackthorn (Prunus spinosa) to make way for the younger 2-3 year old growth that Brown Hairstreaks prefer – with excellent results. By cutting large crescent, or scallop shell, shapes into the hedge line we not only create space for new growth, but also create slightly sheltered alcoves which will warm up more quickly and retain heat. This allows more herb growth and in turn benefits various insect and mammal species, as well as effectively extending the total length of the hedgerow.

scallopLarge blackthorn scallop at Roundshaw, leaving younger plants standing where brown hairstreak eggs were found.

Recently, the Sutton Nature Conservation Volunteers and the LBS Biodiversity team journeyed out to the wilds of Roundshaw Downs with Butterfly Conservation, not just to scallop the blackthorn, but also to survey for Brown Hairstreak eggs.

For this species, the eggs are the most conspicuous and obvious evidence of a population to look for, as the adults spend most of their time high in woodland canopies, and the tiny larvae are small, green and feed on the underside of leaves. Searching for little white dots might not sound easy – and it isn’t – but the eggs are a lot easier to find than other forms!

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Adult Brown Hairstreak

With a large cohort of volunteers we carefully picked through the site’s various blackthorn thickets searching for the tiny white dots of the eggs. Despite the weather’s best attempts we all avoided frostbite, the occasional adrenaline burst that comes with finding an egg proved sufficient to warm us up. Although it must be said that when it’s that cold differentiating eggs from ice crystals can be difficult!

Our morning of searching along the north and south blackthorn hedge lines turned up 65 eggs, up from just 19 found in 2015. Of course, this may be due to a larger team (and there were a lot of us braving the cold!) searching the area more thoroughly, but it is undeniably encouraging to see such a stronghold of a relatively rare butterfly on one of our sites.
What’s more, the areas which had previously been scalloped, mainly on the southern edge of the site, turned up far more eggs than those areas which hadn’t been cut back, showing that our hard ongoing work has been worth it!

bh_eggsThe ‘Sea anemone’or ‘golf ball’ shaped eggs of Brown Hairstreak (Thecla Betulae)  

As a little bonus, on top of this we recorded 16 Blue Bordered Carpet Moth (Plemyria rubiginata) eggs. While this isn’t a particularly rare or unusual species it is the first confirmed record of it on the site, and 16 eggs found coincidentally could suggest a healthy local population of the moth.

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Ovoid eggs of the Blue Bordered Carpet Moth (Plemyria rubiginata)
But what is the ultimate point of collecting this data? Joe has explained before that the Brown Hairstreak is in decline, and at risk of regional extinction. Thus it had been included as a priority species for conservation in the UK Biodiversity Action Plan. This decline is thought to be mainly down to the destruction and improper management of blackthorn hedge lines where Brown Hairstreaks can lay their eggs. Therefore showing correlation between well managed blackthorn hedges like those at Roundshaw Downs and increases in Brown Hairstreak numbers is important in proving that point, and can be used to encourage more sensible management of blackthorn hedges.

Of course, showing that we have seen an increase in the species on a site is always a good thing, especially when the species concerned is a priority species. However it is important to remember that we are a small part of the bigger picture, and what we are really doing is contributing to a huge database of surveys and information collected about these species, which becomes more complete as time goes on and more surveys are undertaken. Using the data collected from this site, Butterfly Conservation can extrapolate certain information by comparing it to other sites on a local and national scale.

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Population Map of Brown Hairstreak

Brown Hairstreak are generally confined to the South of the UK – with strongholds in Surrey and West Sussex, North Devon and South West Wales – however the data collected in Surrey by Butterfly Conservation since 2000 shows trends that the species is actually slowly moving North. Southerly sites in Surrey have seen a marked decline while at sites in the North and West of the county have seen an increase.

As mentioned previously, these assumptions may be slightly skewed. Have the sites with recorded increases of population (like Roundshaw Downs this year) really seen an increase, or is it that they have been more thoroughly surveyed? Had some of these sites not been previously surveyed at all? I mentioned above that we found the first recorded Blue Bordered Carpet Moth eggs at Roundshaw, but that absolutely doesn’t mean that there was no population there previously, just that they hadn’t been recorded.

The only way to verify these trends and gain real meaning from the data collected is through widespread and consistent surveying, both through organised survey days with large groups like our frosty morning with Butterfly Conservation, and through individual recording.

Both individuals and groups can submit sighting information to Butterfly Conservation  via the iRecord Butterflies app, for any and all butterfly species. All information submitted this way will add to the overall database of knowledge, giving a clearer and more complete picture of butterfly populations.

While this blog has focused on Brown Hairstreak the message extends to all species: the more information we collect, the more useful it is.
So get recording – the future of the Brown Hairstreak may well depend on it!

Future flowers

Over the past few months, a huge effort has been invested by SNCV and local Queen Mary’s Woodland volunteers to bring future floral splendour to the woodland. Nature conservation is a discipline that is always informed by science and occasionally, partway by art. Sometimes when restoring habitat, like restoring a painting, one just has to scrape away and start again.

A management objective for the woodland is to diversify its habitat from what was a singularly very shady, ivy dominated woodland. To this end, we have been resetting the light levels across the woodland. Since last winter, work has focused on clearing trees and shrubs and other ‘rough’ vegetation to allow for more open and sunnier conditions through to dappled shade and then fuller shade conditions within the woodland.

This is most evident on the eastern side of the wood, where, after much clearance of invasive cherry laurel and sycamore, the subsequent ground scraping of topsoil created a new bare ground ‘canvas’ to work on. The plan for this area is to create new grassland and herbaceous dominated vegetation zones, with a high diversity of flowers and grasses. These would then be relatively easy to manage through seasonal meadow management, such as an autumn cut and clear and hopefully in the future, conservation grazing.

A new canvas 

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There was little of particular interest from the subsequent spontaneous growth of vegetation from the remaining seed bank: a bit of cock’s foot grass, cleavers, herb robert and some thistles and brambles. This was sprayed off and hoed, to keep the ‘canvas’ free from unwanted species and ready for a new palette of plants to be encouraged.

Next came the new seed sowing, which were undertaken by the Biodiversity Team and volunteers over a number of sessions, from late summer through to the autumn.  Various commercial wildflower and grass seed mixes suitable to the site’s conditions, such as, chalk grassland, woodland and hedgerow were selected (as well as a pond margins mix for the new pond). These were then blended together in various proportions to help widen the range of potential plants to grow within any one area. Most areas were sown with about 5g of seed per square metre, the majority (c.60%) of that being wild grasses. We also planted 75 mature foxglove plants (9cm pots) among the cedar trees. As foxgloves are biennial we shall see their beautiful spikes of purple bells flower next year and hopefully they will then perpetuate themselves.

Seed sowing with woodland seed mix

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Planting foxgloves

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Elsewhere, along one long strip on the south eastern side, we have also invested in experimenting with three contrasting small scale grassland creation techniques. Like elsewhere, the whole area was scraped with a excavator to remove the concrete and any topsoil, to reveal the chalky subsoil below. We then laid down 150mm layer of Meadowmat low fertility soil, a commercial product with a very low nutrient factor. This created a superb base for the introduction and establishment of a wildflower meadow and will hopefully deter those nutrient hungry nettles, docks and brambles.

The three techniques we used were:

  1. 120m² of standard seed sowing of a chalk meadow seed mix
  2. 160m² area covered with  a 25mm deep layer of a commercial product called Wild Flower Earth which is essentially a pre-seeded germinating medium; we chose the peat free option!
  3. 200m² of Meadowmat – a commercially grown wild meadow turf.

From a materials cost and logistics perspective, if you are interested in trying any of these at home, seeding was cheapest (approx £3 per m²) and least effort. Turf laying was the most expensive (£10 per m²) and the hardest work (most labour intensive!) and the Wildflower Earth was nearly the same cost as the turf (£9 per m²) but easier to install by just raking out, although we added some grass seed because it does not include grass seed as standard.

An area of the low fertility soil base sown with chalk meadow mix

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Wildflower earth being raked out

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Meadow turf laying

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Meadow complete!

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A green fuzz of germinating plants can already be seen and we shall watch with fascination how all these areas develop. No doubt additional weeding and a little fussing over will be required to help establish these new plant communities. We plan to carry out more seed sowing and wildflower plug planting around the woodland loop path and other areas next spring, once the new path and additional tree work has been completed this winter.

We’ll be keeping you updated as to how each of these experimental areas works out!

Germinating seed!

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If you want any advice on how to create your own wildlife rich area, please get in touch with the SNCV sncvvolunteers@hotmail.co.uk, chat to the Biodiversity Team biodiversity@sutton.gov.uk or look through the old wildlife gardening pages for some ideas: https://suttonnature.wordpress.com/biodiversitygardens/wildlife-gardening-resources/

Latest Task Programme – Out Now

The new task programme is now out: November 16 – February 17

With the addition of colour coding it hasn’t been easier to see what regular SNCV volunteers and Sutton’s Biodiversity Team will be getting up to and what seasonal nature events are on offer.

As the winter approaches our attention turns to the control of trees and scrub as well as the seasonal maintenance of ponds and wetlands around the borough. And with more work planned to continue the improvements at Queen Mary’s Woodland, there are plenty of opportunities to ‘Help Wildlife on Sutton’s Doorstep’.

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Woodland pond ahoy!

 

An impressive amount of hard work has been accomplished at Queen Mary’s Woodland over the last few weeks by SNCV and local resident volunteers, working alongside the Biodiversity Team. The result a new pond for the woodland!

We knew that common frogs and common toads were present in the woodland and a pond seemed a good idea to further diversify its habitat. We chose a relatively open, sheltered area of the woodland to site the pond in, recently cleared of cherry laurel shrubs, roots and other unwanted vegetation. This will provide the pond with a mix of sun and shade. Enough sun to attract frogs and toads to breed in warmer, shallow margins and encourage good plant growth but also limit direct evaporation of water. Of course, being on free draining chalk, we knew a liner would be required and that meant a lot more work than just digging a hole in the ground. In the ‘old days’, any ponds on chalk would have been hand lined with straw and ‘puddled’ clay (squished and trodden down to squeeze out air pockets  to make a solid, immovable, watertight layer) to hold water and were known as ‘dew ponds’ for watering the livestock pasturing on the Downs. This is something of a lost art and we chose the more efficient and reliable approach of using an artificial pond liner.

With Biodiversity Officer David Warburton at the controls of a 5 ton excavator, we dug down into the underlying chalk and further refined its shape with hand tools. Then with the benefit of volunteer help, a 225m² Firestorm 1mm liner was laid out (and phew, was it heavy!). This has been given copious protection, being sandwiched between sand and a special geotextile matting. Finished off with a covering of chalky soil mix and then sown with a wild pond plant seed mix, the exciting prospect of a new habitat for the woodland was given form.

The pond will be fenced in the near future to safeguard against casual access and allow the pond time to establish, free from disturbance. Hopefully, the coming winter rains will yield sufficient clean rainwater to fill the pond and the pond plant seed mix will germinate to provide a valuable habitat opportunity for common frogs, common toads and a myriad of other animals and plants to breed and thrive next year.

We fully expect this pond to have a ‘dynamic’ water level and it may occasionally dry out. Not all ponds need to have constant water all year (although our UK amphibians need some water into the summer to complete their life cycle from egg to emerge onto land as a juvenile). A great many of our pond species are well adapted to fluctuating water levels within ponds and even drying out. This drop in water levels can be a good thing, by controlling any large fish present, which in a relatively small pond like this, are often be detrimental to the pond’s overall wildlife value, by eating lots of the invertebrates.

We will keep a careful eye on its development over the coming months and if necessary, carry out further planting to ensure we have a diversity of plant species and vegetation structure in the pond and grading into the woodland. Planting and seeding is appropriate on this occasion, given the pond’s location and the lack of abundant wetland habitat in the vicinity to recruit plants from. It will be fascinating to observe it developing over the next few months and years and we’ll keep posting to keep you updated on what we find.

A pond for wildlife can bring a great deal of interest to any garden and does not need to be as big as ours to be of real value for wildlife. Now is a great time to install ponds to harness the autumn winter rains. For more guidance on this take a look at the Froglife website here.

Creating our woodland pond was a big job for us to take on and a very big thank you goes out to our volunteers who made an extra effort in getting the job finished. We just need some water now: so let it rain, let it rain, let it rain!

 

It begins… (taking levels to ensure depth, gradients and top levels are what they should be)

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Smoothing out the base and levelling the surrounding ground

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Sand going in to prevent rock or roots near the liner

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Geotextile woven underliner giving strong protection to liner

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Pond liner unfolds

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More geotextil overliner and sand to protect the liner

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Final fill on top (looking like a bomb crater!)

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New Biodiversity Assistant

Something awful has happened to Sutton’s Biodiversity team…

…It’s got me in it!

It’s Adam Asquith, by the way. Hello everyone!

I’ve been volunteering twice weekly with the SNCV for well over a year now, getting my hands dirty with everything from pulling ragwort, to pulling reeds, to pulling thistle, to pulling a muscle in my back.

Writhing on the floor in a pair of leaky waders after being thwarted by a tough reed may be enough to turn some people off their work, but it’ll take a lot more than that to keep me away. This isn’t a challenge, by the way, if the ancient and vengeful God of Manual Lifting Technique happens to read this.

Building up my knowledge of conservation work watching and listening to Dave, Mark, Alex, Joe and the other SNCV volunteers has given me a real passion to learn more and continue to work on our sites.

Having previously only really done office work under the iron thumb of ‘the man’, rather than practical, useful, tree-huggy (except when we chop ‘em down) work for the good of the environment, I can’t tell you how liberating and energising the last year and a bit has been. Genuinely, since being thoroughly accepted into the SNCV tribe, I’ve been happier and healthier, so cheers all.

The position of Biodiversity Assistant has been vacant since Joe Grainger’s departure earlier in the year to explore new pastures. With his blessing, I am to follow in his footsteps… Nice one, Joe.

Anyway Hi all, I’m Adam, the new Biodiversity Assistant. Adam the pun-slinging, wild food-foraging, mountain-walking, booze-brewing, music-making hippy.

…I normally just go by Adam, though.

…Also, I’m not sure I’m old enough to be a hippy.

Other than being the Biodiversity Assistant I am also a computer programmer/IT guy (I have to get money in somehow), and I play drums and sing in a doom metal band (cheeky link). Recently, we’ve been writing songs about how ruddy lovely nature is, if you can believe it.

If you don’t know what doom metal is, you may want to take the way I used ‘sing’ with a pinch of salt. ‘Yell’ or ‘bellow’ may be better words for what I do. I am fairly unlikely to burst into a heartfelt rendition of ‘My Delilah’ while working, you’ll be pleased to hear, but I can’t promise that I won’t start humming ‘Iron Man’. The volunteers will have to learn to deal with it.

Many of you reading this will know me already. Hello friends.
Those who I haven’t met, I look forward to getting to know you soon enough.

I’ll be updating the SNCV blog regularly in the future, covering the practical work we are undertaking and addressing the hows and whys of doing said work, deepening my own knowledge of it and hopefully yours too.
I’ll also post some in depth looks at certain species or groups that I find particularly interesting on a personal level (i.e. things I can eat), so expect something tasty popping up on here soon!

Cheers for reading,
Adam

A summer pick of ragwort

What a magical day.

I could never have imagined that tugging up ragwort could be such a wonderful experience.

Let me start by explaining I am a volunteer for Sutton Nature Conservation and I am part of a team that assists with habitat management work on a number of wildlife sites in the London borough of Sutton.

I volunteer on a Thursday and have turned my hand to many tasks since I started volunteering a year or so ago, such as raking, cutting down trees, pruning hedgerows, coppicing and pulling weeds! But nothing has compared to the lovely day I had pulling ragwort.

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Roundshaw Downs

The team’s task for the day was to remove ragwort on Roundshaw Downs, Sutton’s largest wildlife site. Ragwort is a biennial plant which is common in grazing paddocks and areas of unimproved pasture. Although a number of myths circulate about ragwort, the chemicals it contains can lead to liver damage if consumed. As Roundshaw Downs, is grazed, ragwort is pulled annually to minimise the risks associate with eating the living plant or dried pieces, which may find their way into hay that is cut as part of site management.

Imagine walking through a meadow full of beautiful wild flowers – names I have been told many times, but still cannot remember – and seeing a glorious array of colours. Yellow, white, blue, pink. The sun was shining and I was watching the butterflies, blue, brown, golden (again an identification memory loss) fluttering from flower to flower resting for a moment to enjoy the heat of the sun.  Imagine too hearing the bees as they work their magic collecting the pollen.

I was lost in the beauty of the meadow. I could have been Shirley Valentine (without the sand, sea and glass of wine) or Julie Andrews in the sound of music (without the singing, thank goodness). For me it was a magical experience, completely lost in my thoughts and day dreams, only realizing, from time to time, that I need to keep up with the rest of the team to complete the task in hand!

What a wonderful day – one of the best.

For more information about ragwort visit – http://www.ragwort.org.uk