On Tuesday we had a great morning in Hembury woods on a ‘Bat and Butterfly walk’. The aim was to see the Pearl-bordered fritillaries that emerge for a few weeks in the spring. Megan Lowe from ‘Butterfly Conservation’ explained that there has been a dramatic decline in the numbers of these butterflies (61% since the 1970s). However there are a few places where they are still doing well, and Hembury is one of them.
The aim at Hembury is to improve the habitat of bracken litter and dog violets which provide the warmth and food sources needed for the butterflies to breed, and for the caterpillars to develop. Ponies are used on the site to help trample down the bracken and churn up the soil which helps the dog violets to grow.
While we were walking through the woods, Helen from the Devon Bat Project described their work to reduce the decline of Greater Horseshoe bats and encouraged us to sign up for the Devon Bat Survey. Bats have also seen a decline in numbers, due to the reduction of open areas within woods. However there is still a large roost of Horseshoe bats at Buckfastleigh. Although on a sunny day there was no chance of us seeing a bat on a walk through the woods, the webcam on the Devon bat project website provides a fascinating window on the behaviour of bats in their roost.
Helen and Megan were joined by John who is the National Trust ranger for Hembury woods. He explained how the woods are being managed to create a mosaic of habitats and increase biodiversity. Priority species include the pearl-bordered fritillaries and small pearl-bordered fritillaries, as well as dormice and summer migrants such as pied flycatchers. The aim is to push back the edge of the wood somewhat, and to create some clearings so that oaks can prosper.
Changes since the Second-World war mean that old coppiced woods have become darker as the canopy regrows and coppicing is no longer continued. This results in a reduction in habitats created by vegetation on the ground layer of the wood. One area of contention is the bluebells in the wood. These are beautiful for a few weeks of the year and much loved by local people. However, although they provide nectar source for adult butterflies, they create cool conditions that are unsuitable for the fritillary butterflies to breed.
Once we reached Hembury fort there were plenty of pearl-bordered fritillaries active among the bracken. These are likely to be mainly male butterflies who tend to emerge a few days before the females. The sunny warm weather meant that the butterflies were very active and rarely settled onto a plant. We saw one butterfly up close, which still had a curled top wing and had only emerged very recently. All the fritillaries we saw were the pearl-bordered rather than small pearl-bordered which usually emerge a few weeks later. The cold weather in March this year makes it unpredictable when different butterflies will emerge.