Saturday, 21 December 2013

Trip report, 14/12/2013 The Geology Trail, Brown’s Folly Nature Reserve

A group of 32 people, plus and minus their cars, gathered at the entrance to Brown’s Folly nature reserve near the top of Farleigh Rise, waiting to be entranced by Elizabeth Devon’s introduction to the Geology Trail that has been marked out through the woods and grassland with blue-topped posts. Elizabeth is one of those rare educators who bring her subject enthusiastically to life by setting the scene of the ‘big picture’ within which the details of the smaller scale, analytical view can be appreciated and understood. She laid out a magnificent coloured wall chart for us to view, on which were mapped out the environmental circumstances in which the surface rocks of different regions of Britain and Ireland were formed. This gave us the awareness of how to look, where to look, what to look for and why we would expect to find it there, which is so crucial to well-informed – as distinct from haphazard - naturalistic exploration and enquiry.
Thus prepared, we set out first of all along the top of the reserve to Site I, possibly an old adit mine whose roof has collapsed and been cleared. Here we were able closely to examine the layer of cream coloured Bath Oolite that was mined for use in the buildings in and around Bath. Informed by Elizabeth’s introduction, we were able to examine the tiny spherical ooids – or hollows where they had been – in full knowledge of how they were formed. Above this was the hard ‘Roof Bed’, which serves as a very clear marker band in rocks seen elsewhere around the reserve.
We continued around the trail in mild, mostly dry and at times breezy conditions, visiting the different sites at which we were able to observe such features as current-bedding – which gives some exposed rocks a striking ridged and grooved appearance, and a variety of fossils. Amongst the most exciting of the latter was a sample of fossil coral, which drew gasps of admiration from people as they took a close look at it with a hand lens.
Back at the car park, Elizabeth handed out some free wall charts and took a small party who were prepared to delay lunch, to see some fascinating fossil burrows through rocks near there. We left richly informed and looking forward to future visits to Brown’s Folly reserve well-prepared to understand the above ground distribution of surface fauna, flora and mycota in the context of what lies below ground – and how, why, where and in what circumstances it got there.

Alan Rayner

Trip report, 07/12/2013 Winter biodiversity in Smallcombe Cemetery

A hardy group of 15 people assembled on a dull damp day at the entrance to the Cemetery to meet Alastair Cowan representing friends of St Mary’s Cemeteries.  Alastair explained the plans for the Cemetery and his hopes that the biodiversity of the site might be enhanced in the future.  We intended to assess what we could find in a morning and due to the season and weather this was going to be limited.  Our task was made even harder by the Council having strimmed the site a day or two before so that everything was covered with a layer of chopped grass.
Having established the need of the day Alastair guided us around part of the Cemetery and we found much biographical detail (on the gravestones) to interest us. 
Despite the best efforts of the Council we were undeterred in our plan to carry out a biodiversity assessment using bryophytes and snails which was still possible if somewhat more difficult.  I explained the technology of the biodiversity assessment for bryophytes (using a dog lead and three canes) and we allocated tasks.  Alan and Marion Rayner were our referees for identifying bryophytes. Andrew Daw set about exploring nooks and crannies for snails, finding an impressive total of 16 species in all, including blind, glass and grass snails.
I think most people expected to find very little, so it came as rather a surprise that in the first circle we found 13 species. We continued for another four circles and each circle took about 15 minutes to examine so that after about an hour and a half we had examined 5 circles amounting to a 250 m2 area. Clearly this detailed examination of the gravestones and grass is more fruitful of species than the traditional “surveying by walking about”. By now everyone was getting a little chilled so we stopped albeit that the method optimises at 20 circles.
The data were assembled and analysed using a method that I have specially developed and applied widely to sites in the vicinity of Bath as well as elsewhere in the UK.
We found a total of 24 species and the data indicated that at least 30 would have been present.  I calculated a Nitrogen (pollution) index and the index was just over 5 indicating that the site is polluted (unpolluted would have an index of around 3).  This therefore established a baseline for us to check as progress is made in the restoration of the site.  Alan and Marion found a further nine species either just outside our circles or on a previous visit so the total of 33 for the site is an indication of the extent of suitable surfaces/niches for bryophytes.
Pollution will presumably continue to be a feature of the site and it was noticeable that the acidic granite and sandstone gravestones had no bryophytes associated with them whilst the alkaline limestone gravestones neutralized the acid and were “fertilized” by the pollution.

Alan Feest

Friday, 13 December 2013

Sad news Friday, 13 December 2013

Dear Bath Nats,

I have just heard the sad news from Gillian Barrett that Peter James, a Past President of BNHS died yesterday. I have no further details, but thought those of you who will remember him would like to know.

Sunday, 8 December 2013

Buttoned Snout moth Sunday, 8 December 2013

A Buttoned Snout moth, a rarely sighted moth in Somerset, was found in my living room of all places on 1st Dec.I live in Oldfield Park and the moth was on the wall behind the TV ! I have never seen one of these before. The photo is not good but enabled the ID to be confirmed by Richard Pooley and others in the Bath Nats moth group. This is one of the few macro species that over-winters as an adult and probably came in from the ivy flowers in the vicinity. An amazing find !

Thanks to Geoff Hiscocks

Wednesday, 4 December 2013

Paul wilkins overwintering pupae Wednesday, 4 December 2013

"Now that moth activity has almost ceased I have turned my attention along with another Bath NATS member to searching for overwintering pupae. This is the first time I have done this since I was a young man back in the 1970's and I found it just as exciting as I remembered, just like searching for buried 'treasure'

From my past experience I have found that searching around the base of mature isolated trees in a field or parkland tends to give the best results. So on this occasion we went to a field in Claverton Down where mainly mature Oak and Ash and the odd Beech were growing in parkland grazed by cattle.

The method used was to very carefully dig with a small hand-fork or trowel immediately around the trunk and buttress roots of the tree to a depth of about 2 inches (50mm) starting about 6 to 8 inches (150 - 200mm) away from the trunk searching through any leaf litter or grass roots as you go. Most pupae will be found in this top layer, if you find that the ground is hard then so would any pupating larvae so try a softer area. If it is evident that the ground has already been disturbed then it's very likely that any pupae here would have already been predated by birds or small mammals.

As one would expect Oak trees can often yield the best results, however on this occasion we were surprised to find that we had better results searching around an old Ash tree than around the couple of Oak trees we tried.

Although we only found a total of just eight pupae of varying shapes and sizes together with a couple of hibernating larvae in a little over an hour it was a most enjoyable pastime on a pleasant autumn morning.

It is very important that when collecting pupae like this that you put the soil, grass and or leaf-litter back as you found it, firming it back down carefully when you've finished searching.  Another thing to consider is that once you have found your pupae you will need to keep them until they emerge the following spring/summer because once they have been disturbed from their 'pupal chamber' in the soil they will need to be protected from predators and the elements.

Now comes the task of trying to identify your pupae which unless the pupae are very distinctive like those of the various Hawk-moths this can be quite difficult with any great certainty.

Start by looking at which species are associated with the particular tree where they were found and then look at which of these overwinter as pupae and whether their normal pupation site is underground?  Then considering the size of the pupa you can start to narrow down what possible species they could be.

One of the identifying features of pupae is the shape and form of the cremaster (tip of abdomen) which can have different arrangements and numbers of 'hooks' and 'bristles' however I have yet to find a definitive guide for this.  There is surprisingly little on the internet on moth pupae although I have found that the website UK Lepidoptera to be one of the best. If anyone knows of a better source then I would be very grateful to know about it.

Ultimately though with a bit of luck and a bit of TLC you will be rewarded with an adult moth the following spring/summer.

Another very useful outcome of collecting pupae is that you can sex the individual pupae with a hand lens or low powered microscope and this can help to find females of a number of species that do not readily come to light in the same way the males do and is particularly useful for finding species that have wingless females such as the Dotted Border or Pale Brindled Beauty which you don't normally see.

To aid future identification of pupae I have photographed each one as shown below noting where and when it was collected and what species of tree it was associated with.

Each pupa has been placed in a separate labelled container so that when the moth emerges I can relate it to appropriate photograph"

Photos to follow