In the spring of 2011 the NT, in liaison with Butterfly Conservation and Natural England, carried out an officially-approved reintroduction of His Grace the Duke of Burgundy to two small and almost-adjacent chalk grassland sites in the Bradenham Valley, west of High Wycombe in the Chilterns. The butterfly had died out there circa 2000. Fortunately, the reasons behind the extinction have been identified and addressed, and habitat conditions have improved greatly. The two sites support other invertebrates with similar requirements to His Grace, notably Small Blue and Dark-green Fritillary butterflies and the rare bee-mimic hoverfly Microdon devius.
The chances of natural recolonisation were deemed extremely slim, though there is a small colony, the last in the south Chilterns, along a railway line over 2km away. This is isolated from a developing matrix of chalk grassland habitat patches in the Bradenham valley by intensive agriculture. The butterfly has declined drastically in the Chilterns during the last 20 years.
In late May 2010 91 eggs were harvested from the Ivinghoe Hills (NT) further north in the Chilterns. These were bred through in captivity by Ched George of BC Upper Thames Branch. From these, 29 adults were released at Small Dean Bank and 25 at Park Wood in the spring of 2011.
Close monitoring, mainly by Ched, revealed a reasonable colony at Small Dean Bank in 2012. The peak count there was 14 (3 females, 11 males) but only a maximum of 2 was recorded at Park Wood.
On Mon May 27th this year, in windy weather which hinders this butterfly considerably, 3 males and 1 egg-laying female were counted at Small Dean and a max of 4 males and 1 female at Park Wood. We undoubtedly under-recorded due to the windy conditions, and would probably have seen twice as many had we visited in calm sunny weather. At least three of the adults seen were freshly emerged, and it is likely that a few more adults are due to emerge. Habitat conditions have improved further. Hopefully enough eggs will be laid during this poor spring to see the butterfly through into next year.
Gaining official approval necessitated 4500 words of reports and letters, plus some emails and phone calls. Both donor and receptor sites are SSSIs, so double approval had to be obtained from Natural England. Internally, all wildlife releases and extirpations have to be approved by the NT's Natural Environment Panel. This required me to write a 1500 word report and attend a Panel meeting. The Panel approved the release but expressed some concern as to the long term future of the butterfly in the Chilterns under a climate change scenario - the Chilterns may become too drought-prone for a butterfly whose larvae depend on Primula leaves that remain green well into the summer. The Panel was, though, impressed by the Trust's vision for recreating chalk grassland in the Bradenham Valley (where several areas are being restored to downland from agriculture or forestry). Hopefully the butterfly will 'take' properly at Small Dean and Park Wood, and then spread to other places within the Bradenham Valley. The butterfly needs some decent weather though, and cannot have laid many eggs yet this season....
5 comments:
The odds of normal recolonisation were considered to a great degree thin, however there is a little settlement, the rearward in the south Chilterns, along a railroad line more than 2km away. Buy an Essay Online This is disengaged from a creating framework of chalk prairie natural surroundings fixes in the Bradenham valley by concentrated farming. The butterfly has declined radically in the Chilterns amid the most recent 20 years.
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