Showing posts with label Desmoulin's Whorl snail. Show all posts
Showing posts with label Desmoulin's Whorl snail. Show all posts

Thursday, 9 February 2012

Notes of a meeting – 6th February 2012 – 10am – Cholsey Marsh.

Present:  Martyn Lane and Debbie Lewis of BBOWT, Paul Chandler, Richard Broughton, Tony Rayner, Mark Gray, Gill Williams, Sue Jeffs, Eileen Watts.

ML and DL from BBOWT introduced themselves and ML explained that they had no firm plans yet for Cholsey Marsh, because the land still technically belonged to Linden Homes, but fencing work had been carried out because Linden had some money available.  Some willow trees had also been felled at the bottom of Ferry Road on the left-hand side, as was evident, because they were overgrowing and gangly.   

On passing it was pointed out that, the right-hand side of Cholsey Marsh (direction of The Four Arches) has a high population of Desmoulin's Whorl snail.  PC also pointed out that another important point was the presence of 120+ winter roost of Corn Buntings (more in hard winters), which are nationally very scarce . Its dramatic population decline in the UK makes it a Red List species. 2 reasons that this site is of national importance.

This side of the reserve may not need any management at all, although it was noted that with the pressures of development more people may be walking in the area.  TR added his concern mentioning that the scrape could hardly be seen, but there was quite a deep channel with no fencing at all.  It was pointed out that it was impossible to fence everywhere.  A population of Common Toads was also noted.

Moving on to the left-hand side (direction of Wallingford) ML confirmed that part of the marsh would be selectively grazed, but as yet no herd had been agreed upon.  TR pointed out that grazing did not work before because gates were left open and nests were destroyed.

ML explained that although sheep fencing had been used, there would be no sheep on the marsh, but it would prevent dogs going through.  He was going to ask for dogs to be kept on leads and hoped that the public would respect this.

At this point PC volunteered to produce a list of birds, which had been recorded on Cholsey Marsh.  Also a good site for Loddon lilies and dragonflies.

Concerns were also expressed about the amount of platforms for fishing (ML) and the amount of litter left on the river bank from the other members of the party.

Moving along to the area adjacent to where the Fair Mile hospital rubbish dump was, a large metal gate has been installed.  However, ML confirmed that there will be no access here for people living in the new development.   In this area, some willows would need to be cleared to make access for cows, if necessary. There will be a permissive footpath cutting diagonally across to Ferry Lane for access to the river bank, where it is hoped to have notices containing information about the marsh, money permitting.

The type of fencing to be erected has not yet been decided – it would depend on the number of people using the path.  At this point SJ pointed out that some funds may be available from the Community Development Trust.  MG stated that it was envisaged that the Fair Mile development would not be a separate community, but integrated into the village.  The question of the old rubbish pit was raised and ML stated that this was still the liability of the National Health Service and they were not touching it at present.

Walking further along the tow path it was noted that willow growth had increased massively where the scrape was and action would have to be taken in this area, but not sure how.  Initial thoughts were to take the tree roots out, but this would need further consideration.

All the old fencing had been taken down and the gates could be taken away for re-use.

It was confirmed that the Thames path team would continue to mow each side of the towpath, but some scrub management may be required on the riverside.

At the boundary of the marsh, it was noted that the present fence was useless.

TR raised a query concerning the wood belonging to the late Col. Evelegh’s son at Bow Bridge, and also queried whether BBOWT would be doing any work on the three islands at the Four Arches where he reported a good showing of Loddon lilies.

Desi the Snail

 Or Desmoulin's Whorl snail.

Desmoulin’s whorl snail (Vertigo moulinsiana), or Desi for short is a tiny Snail that is found on Cholsey Marsh. I am unsure of its status there but apparently, it is doing OK.

This tiny snail, not more than 3mm tall, is found in south and south eastern England around the edges of ponds, streams and rivers. In the warmer months, it lives on the leaves of tall wetland plants when it is easiest to see. Desmoulin's Whorl snail is a priority species on the UK Biodiversity Action Plan.

This species was named after the early 19th century French naturalist, Charles des Moulins.

Is the largest Vertigo species, with a shell height up to about 2.6 mm. It is restricted to calcareous wetlands, usually bordering lakes or rivers, or in fens. High humidity appears to be important in determining local distribution within sites. It normally lives on reed-grasses and sedges, such as reed sweet-grass Glyceria maxima and tussocks of greater pond-sedge Carex riparia and lesser pond-sedge C. acutiformis, where it feeds on the microflora, and in autumn it may ascend taller reeds and scrub. Like all Annex II Vertigo species, it is highly dependent on maintenance of existing local hydrological conditions.

In the United Kingdom, Desmoulin's whorl snail is listed as endangered. Its presence on the site of the planned Newbury bypass caused the building of that road to be postponed; the building works were able to go ahead once the snails had been moved to a new habitat nearby. It is reported to have since died out at the new site.

The distribution of this species is Atlantic (the part of the Palearctic area which is under the direct climatic influence of the Atlantic Ocean), and southern-European. This small snail occurs across Europe as far north as southern Sweden.

Within Western Europe, only the populations in England and Ireland are considered viable.

This species is mentioned in Annex II of the European Union's Habitats Directive.

Population numbers: No accurate figures exist. Though never a common species it is thought, its numbers have reduced recently.

Information gained from various internet sources.





                             Desmoulin's Whorl snail (c) Roger Key