A new colony of one of Europe’s rarest butterflies has been discovered on an RSPB reserve in Cumbria, marking a new milestone for a reintroduction project.
The initial discovery, made by volunteers at RSPB Campfield Marsh, revealed 12 Marsh Fritillary butterflies on an area of rough wet grassland and a later visit by Cumbria Marsh Fritillary Project volunteers confirmed the sightings.
This is the first known natural re-colonisation of Marsh Fritillary butterflies on Campfield Marsh and the only RSPB nature reserve in England where the species is currently present, arising from a successful re-introduction scheme in Cumbria led by Butterfly Conservation, Natural England and DEFRA in 2007.
Once widespread throughout the UK, the Marsh Fritillary has declined severely over the twentieth century and is now confined to the western side of Britain and Ireland.
The number of colonies in Cumbria dropped from over 200 to just three in the year 2000 and by 2004 they faced extinction in the area.
In 2007 conservationists released 42,000 Marsh Fritillary larvae over four sites as part of a re-introduction programme aimed at bringing back the population of these beautiful butterflies to the area.
It’s thought the new colony at Campfield Marsh is a colonisation from one of the initial nearby release sites, Finglandrigg, which is about 5km away.
Dave Blackledge, RSPB Cumbria Coasts Reserves Warden, said: “This is what I love about nature - you can be out with volunteers surveying wildlife and stumble across a new species. People love butterflies and we want future generations to be able to enjoy the sight of them, so this new discovery is definitely a step in the right direction.”
Part of the overall plan of the Cumbria Marsh Fritillary Project is to establish core colonies so the butterflies can increase in numbers in those core areas and naturally expand onto suitable habitats they find for themselves.
Steve Doyle of Butterfly Conservation Cumbria said: “This is a great example of how the RSPB can help butterflies - we would have never stumbled across this remote corner otherwise. It’s fantastic news that the butterflies have expanded and re-colonised and hopefully the butterflies will continue to spread naturally in our four core areas of Cumbria.”
The RSPB and Butterfly Conservation will continue to work together to survey the caterpillars on Campfield Marsh and ensure the habitat is suitable to support the new colonies going forward.
The Marsh Fritillary is threatened, not only in the UK but across Europe, and is therefore the object of much conservation effort. The butterfly was once widespread in Britain and Ireland but has declined severely over the twentieth century. The Marsh Fritillary populations are highly volatile and the species requires extensive habitats or habitat networks for its long term survival. It is now confined to the western side of Britain and Ireland.