Monday, 17 August 2015
A Rather Special Butterfly Walk
Last Saturday afternoon we made our way over the county border into Worcestershire to attend an organised Butterfly Walk held on a Higher Level Stewardship farm.
The one species I was really hoping to see was a Brown Hairstreak (Theola betulae) or an Ash Brownie as it is affectionately known. There is a colony of Brown Hairstreaks on the farm.
The Ash tree in the photo below is believed to be the local "Master Tree". Males, which are more elusive than females, congregate round the tops of Master Trees looking for a mate and feeding on honeydew. Females also spend time around the same tree until they are ready to lay eggs.
As we walked along the lane you couldn't miss the profusion of Blackthorn bushes covered in maturing sloes.
Blackthorn is the main food plant for Brown Hairstreak larvae.
We had been told that a female Brown Hairstreak had been spotted feeding on Knapweed in the hedgerow on the Saturday morning and lo and behold here she was in exactly the same place.
To say I was over the moon is a slight understatement as this was a life butterfly "tick" for me. The butterfly continued to stay on the same flower giving everyone on the walk a chance to take a photo.
Brown Hairstreaks are the largest species of British Hairstreaks. Sadly, long term trends show this butterfly is undergoing a severe decline. One of the main reasons for this is the unsympathetic farming practice of removal and flailing of blackthorn in the hedgerows which destroys the over-wintering eggs of this species. (I hasten to add that this most certainly did not apply to this particular farm!).
Brown Hairstreak are a UK BAP (Biodiversity Action Plan) Priority species. The species has just one generation a year with the adults emerging in late July/early August. They are a local species living in colonies that tend to breed in the same localities year after year. They occur in habitats where Blackthorn, the main larval foodplant, is abundant. Adults will take nectar from Bramble, Devil's Bit Scabious, Hemp Agrimony, Hogweed, Ragwort and thistles as well as taking honeydew/sap.
Eggs, which resemble miniature sea urchins, are laid on the bark of Blackthorn (occasionally other species of Prunus such as Bullace are used) usually in a fork on a branch in sheltered areas exposed to sunlight. The larvae undergo partial development and then overwinter within the egg which makes them very vulnerable to hedge trimming as the eggs are laid on the youngest growth.
Caterpillars emerge from the egg in the Spring and following the first moult they will hide during the day in a silk pad on the underside of the leaf emerging at night to feed. They pupate amongst leaf litter or at the base of a plant after the third moult.
Over 400 eggs were found on this farm last Winter during surveying work by the West Midlands Branch of Butterfly Conservation. Little blue tags, as shown in the photo below, show the location of each egg found.
We left the lane to walk along wide field margins where wild flowers and butterflies flourished. It took me back to the countryside of my childhood when butterflies were everywhere and just shows the huge benefits of a farm managed for wildlife under a Higher Level Stewardship Agreement with Natural England Huge credit must go to the farm for all the hard work they have put in to develop an environment where butterflies and birds are so abundant.
Butterflies seen on the three hour walk included:
Meadow Brown (Maniola jurtina)
Green-veined White ( Pieris napi)
Small Copper (Lycaena phlaeas) - my first of the year!
Dozens of Common Blue (Polyommatus icarus)
Small Skipper (Thymelius sylvestris) or is it an Essex as originally thought? Were there ever two harder species to tell apart?!
Brown Argus (Aricia agestis) - another new species for 2015.
We also spotted Large and Small Whites, dozens of Gatekeepers, Speckled Wood, Ringlet, Comma, Small Tortoiseshell and I think possibly a couple of others that we missed as we'd lingered to take photos.
Day-flying moths included several species of Grass Moth (Crambidae), Silver y, Straw Dot and Shaded Broad-bar.
There were so many highlights during the afternoon and a sighting of a Roesel's Bush-cricket (another "lifer" for me) was the icing on the cake.
Roesel's Bush-cricket (Metrioptera roeselii) was found only in the South-East of England in the early twentieth century but there has been a rapid expansion in its range northwards and westwards in recent years. Roadside grassland and scrub have acted as "corridors" and allowed it to travel to new areas.
We finally returned to the farm and were treated to homemade cakes and tea - a lovely ending to a wonderful afternoon.
Every single hectare of Upper Hollowfields is farmed sympathetically to benefit wildlife under a Natural England Higher Level Stewardship Scheme. For example, wild bird mixes have been sown, hedge management is undertaken on rotation taking into account the requirements of different species including Brown Hairstreak, wild flower meadows have been created, a wet meadow of botanical importance has been allowed to naturally regenerate, scrapes have been created for waders and an orchard is currently being restored. 80 species of bird have been recorded on the farm.
I appreciate not all farms qualify for HLS but it was exceedingly interesting and uplifting to see what a difference farming in an environmentally friendly way can make for wildlife.
Many thanks to GC who led the walk for his knowledge, friendliness and enthusiasm (and for finding a BH for us all to see!!) and to Wild Hollowfields who hosted this superb event.
Most of the photos above were taken by David with the Canon Bridge which far outshone the Olympus dslr and 70-300 lens! The photos with an asterisk underneath were taken by me with the Olympus.