Suffolk Valley Fens Naturetrek Tour Report 15th – 29th August 2020 Common Darter (Su Gough) Fen Raft Spider (Su Gough) Grass of Parnassus (Marion Marshall) Southern Migrant Hawker (Marion Marshall) Report compiled by Su Gough Naturetrek Mingledown Barn Wolf's Lane Chawton Alton Hampshire GU34 3HJ England T: +44 (0)1962 733051 F: +44 (0)1962 736426 E: [email protected] W: www.naturetrek.co.uk Suffolk Valley Fens Day Trips Report Summary All five of the day trips to the Suffolk Valley Fens, led by Su Gough, have run fully booked and all have enjoyed the intriguing flora - especially Grass of Parnassus at its best - and the plentiful invertebrate life associated with the fens. The Fen Raft Spider, Britain’s largest spider, both elusive and extremely rare, has been found on most trips, a fine conclusion to a wonderful day spent exploring this little-known series of reserves and special places on the Norfolk/Suffolk border. Yellow Loosestrife Bee (Su Gough) Harebell (Su Gough) Saturday 15th August We met at Market Weston Fen in pouring rain which didn’t bode well, but it quickly cleared and luckily held off for the rest of the day. Low overhead was a big group of Swallows and House Martins feeding up before leaving for the winter and joining them were a couple of very late Swifts. As we stood on the bridge at the entrance to the fen a Kingfisher shot past our heads, and then a Hobby suddenly appeared, drawn by the flock of martins and swallows. The morning was spent enjoying the range, number and diversity of wildlife at this jewel of Suffolk Wildlife Trust’s reserves, before heading on for lunch outside the fully functioning and very picturesque Thelnetham Windmill. After lunch we marvelled at the sheer number of orchid seedheads at the nearby Thelnetham Fen and enjoyed a sighting of a handsome male Banded Demoiselle damselfly before moving on to the larger Redgrave and Lopham Fen. Here we did, finally, find a young Fen Raft Spider but perhaps the most surprising and exciting sighting was of a Yellow Loosestrife Bee, a rare and range-restricted species that was not known at this site. Sunday 16th August The group met in much kinder weather but the darkening clouds warned of an impending thunderstorm. Remarkably we avoided the rain all day – with our morning at Market Weston Fen warm, sunny and very, very © Naturetrek 1 Suffolk Valley Fens Day Trips Report humid with thunder rumbling around us. In the still, humid conditions at Market Weston Fen invertebrates were particularly noticeable, with a surprise find of a Wasp Spider delighting everybody. One of the many Silver Y moths in the fen habitat also turned out to be the scarce Dewick’s Plusia moth. Thankfully the rain didn’t start until we made it back to the cars but continued ‘enthusiastically’ over lunch before stopping again in time for the afternoon walks. As the group were keen photographers and enjoying the insects, we decided to adapt the itinerary and go to Redgrave and Lopham Fen first after lunch as more rain was forecast later in the day. Another Fen Raft Spider was found, along with a total of 17 Yellow Loosestrife Bees confirming this as a new colony and, most surprising of all, a stunning male Southern Migrant Hawker dragonfly, a very rare recent colonist, joined us while we were watching the spider! With an hour to spare, but with thunder clouds once more ominously building, the group all decided to leave the day on a high – a good decision as the heavens opened shortly after. We later discovered that the lunchtime storm had delivered a quarter of the expected annual rainfall to a nearby village in just one hour, we could certainly believe it! Saturday 22nd August Common Blue (Su Gough) The group were lucky with a warm, dry day although it was pretty breezy which did keep some of the insects well hidden, although the whole group were able to get very close-up views of a male Migrant Hawker dragonfly sheltering in the vegetation. Thelnetham Fen delivered excellent views of a young Hobby - which dived down and caught a dragonfly - and three Grey Herons hunting the plentiful frogs in an area of recently cut grazing marsh. We also considered the strange non-stinging Stinging Nettles growing in the fen. As a large site, Redgrave and Lopham Fen is fairly exposed but in a sheltered area of wet Sallow woodland we discovered the strange egg-laying scars of recent colonist Willow Emerald damselflies high above the mud in an area which dries up in the summer. The rain over the previous week had refilled many of the spider pools, which did mean there was much more habitat for us to scan but it also meant that the adult spiders had come back and eventually we located not one but two stunning adult females, as well as drawing a bit of a crowd of interested members of the public! Sunday 23rd August A dry and only slightly breezy day, with very comfortable temperatures made for perfect weather for exploring the fens. At Market Weston Fen we got our first chance to consider the differences between Common and Ruddy Darter dragonflies and every time we were on a bit of boardwalk we were accompanied by Common Lizards. Some of the Ivy thickets had just come into flower and a brief scan revealed the first handsome Ivy Bees of the season. The plentiful Water Mint on the site also delivered Mint Moths, a micro moth which previously everyone had only ever seen on cultivated herbs in gardens and Marsh Fern and seedheads of Water Plantain reminded us that we were on a wetland site. © Naturetrek 2 Suffolk Valley Fens Day Trips Report The Great Burnet growing on the ‘schwingmoor’ at Thelnetham Fen was admired in this outlier location for this typically northern and western species along with drifts of Devil’s-bit Scabious which shone in sunlight warming the fen. The group took a little time to identify an abundant fern (Narrow Buckler Fern) growing in clumps under the wet woodland - such a common sight in so much of the country but rare in East Anglia, especially so near the dry sands of Breckland. As we walked around, we saw several striking Roesel’s Bush Crickets, once rare but over the last 20 years increasing their range. At Redgrave and Lopham Fen we were able to compare the Common Emerald Damselfly with the Willow Emeralds which we eventually found near the egg scars spotted on previous visits and we rounded off the day with close views of a female Fen Raft Spider. Saturday 29th August In typical August Bank Holiday style the group met in cool and breezy conditions with rain forecast during the day. The morning spent at Market Weston Fen remained dry and the huge number of flowers were thoroughly enjoyed. Comments were made on the number of bumblebees – of a number of species – that were roosting on flower heads in the unseasonal conditions. Almost all chose heads of the plentiful Devil’s-bit Scabious and made an unusual sight. Three Buzzards flew low overhead and then circled above us, while Marsh Tits were suddenly obvious on site once more, having finished their post-breeding moult. Everyone got very close views of a lovely female Common Darter roosting on a plant and several new plants were found, including Fleabane and Brookweed. After lunch, the group enjoyed a pleasant walk around Thelnetham Fen and the adjoining Little Ouse River. Hops were conspicuous with large amounts of fruit hanging from the trees, and the Pedunculate Oaks were covered in various different types of wasp galls. A large female Fen Orb-web Spider was discovered nestling in the Purple Loosestrife and a pair of Muntjac entertained us. By the time we arrived at Redgrave and Lopham Fen the rain had settled in for the day, although the wind had dropped. Sadly, the rain dimpling the surfaces of the spider pools, and the fact that the water had risen so much, meant the surrounding reedbeds had open water and we didn’t catch up with the Fen Raft Spiders, but we were delighted to spot several roosting Willow Emerald damselflies very close Wasp Spider (Su Gough) to the path. © Naturetrek 3 Suffolk Valley Fens Day Trips Report Species List Scientific Name Common Name 15-Aug-20 16-Aug-20 22-Aug-20 23-Aug-20 29-Aug-20 Equisetaceae Equisetum arvense Common Horsetail X X X X X Equisetum palustre Marsh Horsetail X X X X Equisetum telmateia Giant Horsetail X Pteridophytes Pteridium aquilinum Bracken X X X X X Dryopteris carthusiana Narrow Buckler Fern X X X X Thelypteris palustris Marsh Fern X X X X Pinaceae Pseudotsuga menziesii Douglas Fir X X X X X Ranunculaceae Ranunculus acris Meadow Buttercup X X X X X Ranunculus flammula Lesser Spearwort X X X X X Ranunculus repens Creeping Buttercup X X X X X Thalictrum flavum Common Meadow Rue X X X Papaveraceae Papaver rhoeas Poppy X Ulmaceae Ulmus Elm sp. X X X Moraceae Humulus lupulus Hop X X X X X Urticaceae Urtica dioica Nettle X X X X X © Naturetrek 1 Suffolk Valley Fens Day Trips Report Scientific Name Common Name 15-Aug-20 16-Aug-20 22-Aug-20 23-Aug-20 29-Aug-20 Urtica galeopsifolia Fen Nettle X X X Fagaceae Quercus robur Pedunculate Oak X X X Betulaceae Betula pendula Silver Birch X X X X X Betula pubescens Downy Birch X X Alnus glutinosus Alder X X X X X Corylus avellana Hazel X X Chenopodiaceae Chenopodium album Fat Hen X X Caryophyllaceae Stellaria graminea Lesser Stitchwort X X X Stellaria media s.s.