One warm sunny evening early last July, the idea of finding a glow-worm came to mind.
Realistically it was a long shot.
The last time Denise and I had seen a glow-worm had been ten years previously, on a cliff-top near Portscatho, on the Roseland Peninsula in Cornwall. I did some quick digging on the internet, remembering a website devoted to UK Glow worms that contained county by county records of historic sightings. Sure enough, a site not far away between Hertford and Broxbourne showed some potential, so we jumped in the car and set off.
After a few minutes drive through Hertfordshire lanes we pulled over when we thought we were in the right place and took a pleasant stroll round the surrounding woodlands, eyes peeled for our quarry. As darkness approached it seemed our search would be fruitless. However, returning to our starting point we came upon a small gathering.
“Are you here for the glow-worms?”
“Well, yes actually” we replied, somewhat surprised at the accuracy of the enquiry…..
“Splendid, thanks so much for coming”
Confusion was resolved on learning that the group, led by June Crew and Frances Green, had assembled to survey the wood’s glow-worm population, including some tentative early research on male glow-worm responses to varying light sources. After a crash course from June in our invertebrate quarry and with peak glowing time fast approaching, the party departed and the search began in earnest. We learned so much in such a short time that evening, as well as experiencing again the magical moment of finding three or four glowing in the grass.
The following night, armed with the knowledge of likely appearance times after sunset and an appreciation of where to look, we set to investigate an area much closer to our home. It had transpired from the previous evening’s conversation that June had surveyed an area near our home some years before and had turned up one glow worm sighting. Surely then, inspired by the previous evening, it was worth a look. But as we made our way along the footpath in the dusk of another glorious summer’s evening, we prepared ourselves for the possibility that this might be a long and fruitless search.
How wrong we were.
Barwick Ford is located in North East Hertfordshire, sitting in the valley of the River Rib, four miles south of Standon. The Rib is a chalk stream, well known to geographers for it’s meandering profile and oxbow lakes that rises close to Kelshall near Royston and joins the River Lea just west of Ware. North-east of the ford, accessed from the footpath that leads to Latchford and Standon, lies a field of set aside land – it was here that we were to look.
Emerging from the dark canopy of the footpath opposite one of the farm buildings that are nestled in the field, we began to carefully search, treading delicately through clumps of thigh high grass, eyes straining, imagining luminescence where it wasn’t. A few minutes passed, then the rush of success as eyes fell upon a gently glowing green jewel, deep amongst the turf. A few more twinkling gems followed on that first night – a thrilling experience and the confirmation we needed that Barwick Ford did indeed still provide habitat for the glow worm Lampyris noctiluca.
Inspired by Frances and June’s work, we set ourselves to survey and document the population as best we could, returning over following nights to count the females as they glowed to attract a mate. On our first visit we searched the field edge, matching habitat that we had seen at Monks Green. The following night we searched further round the field. Initially our wanderings were pretty random, but by our 3rd visit we felt we had identified four patches across the site in which to record the location of glow worms, to see if particular areas of the site might be favoured.
Due to the extent, thickness and height of the long grass, over successive nights we inevitably began to take a consistent path around the four areas. We changed our search circuit direction each night to balance out searching times in each as it was now taking 30 minutes to cover the area. As the surveying developed, it became clear that glow worms could appear in almost any part of the field, suggesting a more systematic approach would be needed to conduct a full survey of the site in future seasons. The grass though will always be challenging to searchers so advice is welcomed on future surveying techniques. However, even with these restrictions and as the table below shows, we recorded a total of 150 glowing females over a 20 day period through most of July, with a mean average of approximately 10 showing per night and a high count of 19 on 11th July.
|15 Jul||no survey||0|
|16 Jul||no survey||0|
|17 Jul||no survey||0|
|19 Jul||no survey||0|
|24 Jul||field cut||C||2||2|
|26 Jul||field cut||C||1||1|
The most obvious and clear conclusion that can be drawn is that the glow worm is present in reasonably significant numbers on the site.
Their presence at Barwick Ford haduntil now had been unknown aside from June Crew’s lone sighting in the last 10 years and a recording of large numbers being seen in the summer of 1971, found on the UK Glow worm county by county records page.
Other anecdotal records gathered locally indicate that glow worms had been present in the back field of the (now defunct) Duke of Wellington/Factory Arms public house in Barwick up until 20 or so years ago, though searches around the village have so far proved unproductive.
The field in which the Barwick Ford site is contained is split between agricultural crop (typically oil seed rape or cereal) and set aside land and is owned and managed by the Chaldean Estate in Much Hadham. I believe the set aside land is supported through an EU Stewardship Scheme (which one hopes and trusts will be replicated in some form post-Brexit). But on investigating further back, one discovers that the field formed part of a gunpowder factory, the land for which was purchased from the Youngsbury Estate in 1888. Despite an explosion in 1893 the factory continued as an ammunitions and mining explosives factory under various owners well into the 20th Century, indicating that the land itself has been unimproved in agricultural terms for quite some time.
One imagines that due to the changes in farming practices since World War II and the reducing amount of ‘historical’ unimproved land, glow worms are unlikely to be present locally except for in this currently defined site, due to the sedentary nature of the females and larvae. We will however continue to search in future years and hopefully discover more natural history secrets contained in this quiet chalk stream valley.
Having put the Barwick glow worms back on the map, our hope in future years is that more people are able to share in the spectacle. We remain in contact with and indebted to the Chaldean Estate for their interest and support and hope that with them we can arrange a series of glow worm walks in 2017. Check out the site for further details as the season approaches.
Our sincere thanks to June Crew and Frances Green for our fascinating crash course in glow worms.
Thanks also to Anne Peacock and Sally Bond at Chaldean Estate for their interest and for sharing the information on the glow worms in their estate newsletter and to Ian Carle, HMWT Records Centre Manager for his support and correspondence.
UK Glow worm Survey – http://www.glowworms.org.uk/
UK Glow worm page – Historic sightings by county
History of Barwick – https://en.wikipedia.org/wiki/Barwick,_Hertfordshire
Historic maps of the area –http://maps.nls.uk/geo/explore/sidebyside.cfm#zoom=17&lat=51.8549&lon=0.0106&layers=6&right=BingHyb