Common Wood: part 7
When I bought Common Wood on 19 October 2011 I had not realised it was potentially a butterfly hot spot. Then Jenny Plackett, Butterfly Conservation’s Two Moors Threatened Butterfly Project Officer, told me it had the potential for Marsh, Pearl-Bordered and Small Pearl-Bordered Fritillaries. Now I am learning how to improve the habitat to attract these species—and it’s not straightforward.
Fortunately, Jenny, ecologist Hil Marshall and the Dartmoor Preservation Association volunteers have been invaluable in advising me and helping to make the habitat more butterfly-friendly.
Common Wood, in the parish of Mary Tavy on western Dartmoor, is on a steep, south-east facing slope adjoining the River Tavy which runs along the bottom. It is bisected by a leat, with a public footpath running along the eastern side.
Much of the land is wooded, but on the upper part, above the leat, there is some open ground (A on the map). The top is grassy, but as one moves down the slope the bracken increases until it becomes scrub then woodland.
With the help of the DPA volunteers, we have been clearing the vegetation lower down so that it is suitable habitat for the Pearl-Bordered and Small Pearl-Bordered Fritillaries (see previous blogs under the Common Wood tab).
We have spent five days there over the last three years and have made good progress, removing much of the gorse, hazel and bracken and piling it to make a windrow above the leat (a nice habitat for birds, and much better than burning).
However, we need cattle to keep the vegetation down and to make paths through the bracken. A nearby farm has rights to graze this part of the common for some of the year, but when the gate is opened to let the cattle through, they tend to stay near the top where the grass is sweeter. We could do with more trampling and have cut tracks through the bracken to encourage the cattle to come down.
The flat land between the leat and the river is rare Rhôs pasture (B on the map), quite wet and open and suitable for Marsh Fritillaries. Here we need Devil’s-bit Scabious (Succisa pratensis), the butterflies’ food plant, to thrive.
This requires a certain amount of grazing but not too much. A local farmer grazes the land on the other side of the river. In August, after he has put the cows to the bull, he moves them into a separate field which adjoins the river. The cattle come down to drink and when the river is low they cross it and graze the marshy area.
That is good provided they graze it at the right level. Last summer the grazing was too much and there weren’t many Devil’s-bits left.
It’s a fine balance and depends on the height of the river at the time the cattle are in the adjoining field. The problem is that there is no way of stopping the cattle from crossing the river—I offered to fence the other side but then the cattle couldn’t get access to drink. It is too difficult to provide a bowser here. So you can see that it is complicated.
Jenny and I discussed it with the farmer last September and he was very accommodating.
Next year he will ring Jenny when he puts the cattle in the field, usually in the first week of August. Four or five days later Jenny will arrange for a visit to check whether the cattle are grazing the marsh and, if so, will determine when they should be removed. The farmer has agreed to cooperate with this, although I appreciate that early removal is annoying for him (on the other hand, he is getting some free grazing).
Fortunately the local farmers understand the importance of encouraging the Fritillaries, to make a corridor for them along the Tavy valley. It will be a slow process. With lots of help, Common Wood can become a Fritillaries’ haven—and heaven.