DHBlog030 · Report on the event held jointly by the Dorset Flora Group and the Dorset Branch of Butterfly Conservation, 19th July 2023
By Tom and Jean Smith
In addition to being active Dorset Flora Group members we normally lead a walk or two each year for the Dorset Branch of Butterfly Conservation, who asked us whether we’d like to lead a joint walk this year. We took up this suggestion and decided that Dorset Wildlife Trust’s Winfrith Heath reserve would be a good site for interesting plants and butterflies.
We managed the pre-walk on Monday 17th July and were delighted to find Bog Orchid’s helped by an 8-figure grid reference. The most surprising aspect of this recce was finding and recording 21 species of butterfly. We parked on the verge opposite the reserve, and this was well stocked with wildflowers including Weld (Reseda luteola), Great Mullein (Verbascum thapsus), Soapwort (Saporina officinalis) and Teasel (Dipsacus fullonum). Consequently, on this sunny day it was humming with Butterflies, Hover flies and Bees. We saw a Dark Green Fritillary here among several other species including Gatekeeper, Marbled White, Common Blue, Meadow Brown and Peacock. The rest of the pre-walk went very well, and we had sunshine throughout which helped us see a Purple Hairstreak on one of the Oaks a short distance from the ‘Prison Fields’ area of the site.
Two days later we arrived early for the event but were disappointed to find that the wildflower verge had been mown for its entire length, leaving nothing in flower, no butterflies, but easier parking! Fifteen of us gathered for this trip on a warm, bright morning. Initially we explored the southwestern part of Winfrith Heath. Here the habitat includes wet and dry heath and some small areas of acid grassland a copse and a strip of woodland habitat along the boundary path.
Some of us were soon on our hands and knees looking at Thyme-leaved Sandwort (Arenaria serpyllifolia) and Sand Spurrey (Spergularia rubra). We spent some time looking at nearby scrapes to see what was about. No Graylings, but we did see a Bee Wolf, which as their name suggests prey on Bees.
Moving on we went past a small copse then along the boundary path so were not surprised to find Speckled Wood in this area. Emerging out on to the open heath we started seeing our first Silver-studded Blues of the day, more or less equal numbers of males and females. In the wetter areas we were finding Bog Asphodel (Narthecium ossifragum), White-beaked Sedge (Rhynchospora alba), Round-leaved Sundew (Drosera rotundifolia) and Oblong-leaved Sundew (Drosera intermedia) and Deergrass (Trichophorum germanicum), so plants all characteristic of wetter heath.
Eventually we reached the minor road that separates this part of Winfrith Heath from the main part of the site. The verges and ditches here provided more variety including Bog pimpernel (Anagallis tenella) and Yellow Rattle (Rhinanthus minor). This was also where we saw the only Ringlet of the day; a species which seems to be having a very poor year.
We then carefully found a route through Molinia tussocks to an area of wet heath. This is where, with the aid of an eight-figure grid reference we saw Bog Orchid (Hammarbya paludosa) in a boggy area with a slight flow of water.
The flowering stems of these orchids are only about three to eight centimetres tall and very hard to see, so we were on our hands and knees searching for them. On the day we discovered that there were about 6 plants in total in two distinct groups with Carolyn Steele finding the second group. Nearby Jon Crewe also found Pale Butterwort (Pinguicula lusitanica).
By now it was lunchtime, so as it was sunny, we headed to a shady spot not far from the cars in the main part of the reserve. During lunch it clouded over so during the afternoon fewer butterflies were noticeable except in sheltered, warmer areas. Our plant list was still growing and at the edge of a ditch alongside the main track we found one of our target species Great Burnet (Sanguisorba officinalis) and also Marsh St John’s-wort (Hypericum elodes). On the track itself were Lesser Centaury (Centaurium pulchellum). As we approached the edge of the Prison Fields, we saw the only Painted Lady of the day. From here we crossed some more dry heath where we saw several Silver-studded blues, Small Copper and numerous Gatekeepers. A tiny plant (with minute white flowers) on the track here proved to be Allseed (Radiola linoides). Finally, we reached a ditch about 15 metres north of Tadnoll Brook and here we saw both Yellow Loosestrife (Lysimachia vulgaris) and Purple Loosestrife (Lyhtrum salicaria) and Marsh Valerian (Valeriana dioica). As time was getting on, we concluded our walk by heading back up to the cars along the main track.
In total we saw 19 species of butterfly on this trip: Silver-studded Blue, Common Blue, Holly Blue, Small Copper, Peacock, Red Admiral, Painted Lady, Small Copper, Brimstone, Small White, Large White, Small Heath, Gatekeeper, Meadow Brown, Marbled White, Ringlet, Speckled Wood, Small Skipper and Large Skipper.
Other fauna included a Bee Wolf, Golden-ringed dragonfly, Common Darter Dragonfly, Banded Demoiselle and a frog and a Common Lizard.
Our thanks to all who attended and contributed their expertise and enthusiasm and to Dorset Wildlife Trust for allowing this event. Special thanks to Kevin Denham for the excellent photographs.