FIELD NOTES
APRIL 2002 continued....
The Natural History of The Commons
by Peter Oakenfull, Reserve Warden
The Commons is a Local Nature Reserve owned by Welwyn Hatfield Council. It is situated on the edge of WGC on the south east side, near to the QEII Hospital (TL259111). It covers about 35 acres and has a diverse habitat including fen, meadow, arable and two small brooks. Although not officially opened until 1998, species recording has been carried out there since 1995 and bird ringing since 1994.
Peter Oakenfull and Keith Seaman have been monitoring Harvest Mice and other small mammals on the site; Common, Pygmy and Water Shrews, Wood Mice, Field and Bank Voles are all found on the reserve. Part of Windmill Hill is managed as grassland for small mammals. There is a high population of Grass Snakes , and, six years after construction, an artificial Badger sett is now inhabited.
The upper part of Windmill Hill (about 5 acres) is managed for farmland birds, largely organically. A spring crop of mixed cereals is sown in late March as winter food for birds such as Reed Bunting, Yellowhammer, Goldfinch, Chaffinch and Skylark (which have bred for the last 2 years). Among the arable wildflowers at the site are Corncockle, originally grown from Hertfordshire seed and now self-generating, as well as Cornflower, grown from seed harvested in London Colney. As the reserve is not rich in hedgerows, many of these birds use the arable and its surrounding headland as winter-feeding grounds.
In the northern part of Black Fan Fen there has been little conservation work . The more domed southern part, which in 1996 was covered in brambles , has been flailed . This winter a pond and wet scrapes were created, primarily to encourage Snipe, which were last recorded on the reserve in 1997. The work was finished in November 2001. Since then there have been 5 records of Snipe. The new features are also expected to improve the habitat for dragonflies and Denis Shepperson from the Herts Dragonfly Group has been invited to record there in the summer. It is also hoped that Great Crested Newts, known to occur locally, will colonise the pond.
Hatfield Hyde Brook forms the southern boundary of the reserve. This has a small Water Vole population and management work has been carried out to create more suitable habitat with the removal of scrub along the banks.
When Howland's Meadow was first surveyed some years ago by Trevor James , it was rapidly evolving into woodland, due to invasion by Ash. Regular work parties have coppiced the Ash and much of the unimproved meadow has been restored. Peter has recorded 27 species of butterfly at the reserve, including the Ringlet and White-letter Hairstreak. Elm is the food and over wintering plant for the latter.
The elm is coppiced selectively during the flight period in July to prevent the trees increasing in girth to a size where they will succumb to Dutch Elm disease. The meadow also supports many wild flowers including a substantial colony of Bee Orchids. A small flock of Hebridean sheep are now resident on the reserve and are used in the management of scrub and grassland.
The reserve is managed by Commonswood Nature Watch. This dedicated committee of 10 members are committed to carrying out the work and have achieved great success over the years. They also involve the local community, local businesses (such as Three Valleys and Thames Water and Marks and Spencer) as well as local children.
This reserve is well worth a visit. Entrances can be found at grid references TL258111, TL259114 and TL254112 so put it on your agenda for a visit soon.
Caddis Flies of Hertfordshire
by Dr Ronni Edmonds-Brown of the University of Hertfordshire
Caddis Flies are members of the order Trichoptera, which means 'Hairy wings' and have a long history stretching back to Permian times. They are widespread globally, except for Arctic regions and although not generally colourful, are fascinating insects with 18 families and 191 species known in the UK. The County list is being worked on currently; so far no Red Data Book species are known in Herts.
Most caddis flies have an annual life cycle, with four stages; egg, larva, pupa and adult. The majority of the cycle is spent as a larva in a wide range of watery habitats, from fast flowing streams to lakes and ponds. They may be free living, net spinners or live in the well-known cases made of stones and other debris. At the University of Hertfordshire field station at Bayfordbury, several species have been bred and studied through all their life stages. Valuable information has been gathered about their biology and reproductive rates, which has enhanced their already useful role as fresh water quality indicators and can help with conservation planning. Under new plans an industrial greenhouse at the field station is being converted into an Indoor Aquatic Centre . This conversion , sponsored by the Environment Agency , will soon have an artificial stream and ponds for rearing aquatic invertebrates .
Good taxonomic keys are available for UK species, which will help those who would like to learn more and perhaps start recording . Next Autumn and Spring , Dr Edmonds-Brown will be running collecting and training sessions, which are open to HNHS members. (Contact: Dr V Edmonds-Brown, Dept of Environmental Sciences, University of Hertfordshire, College Lane, Hatfield, AL10 9AB, Tel no: 01707285254, Email: V.R.Edmonds-Brown@herts.ac.uk )
Christine Shepperson
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