The Heart of Durham project was initially set up to halt the decline of one of the UK’s most endangered resident butterflies, the small pearl-bordered fritillary butterfly.
Working in partnership with Northumbrian Water, Durham County Council and Butterfly Conservation, the project is reversing this decline.
With a £120,000 funding grant from the SITA Trust Enriching Nature Fund, as well as a Northumberland Water- Branch Out grant of £6,000, the project has been working successfully with landowners and project partners to restore and link habitats and sites to develop wildlife corridors. These ecological routes through the countryside are important for many species of animals, reptiles and invertebrates, but especially those species that have a low dispersal ability such as the fritillary butterfly.
Ten sites were selected as a result of studies on existing colonies, site surveys and historical records of SPBF presence and practical management was carried out to:
- enhance and expand the habitat were existing colonies were present
- restore degraded habitats to a condition to support new colonies
Since 2010, the Heart of Durham project has increased this suitable habitat area by 40% and aims to continually increase this as it works on a landsacpe scale.
Habitat improvements have focused on planting propagated marsh violets the caterpillar’s main food plant.
With the help of the grants the project has re-established over 3000m of hedgerows and 140m dry stone wall providing valuable sheltered areas for the butterfly to breed and 770m of fencing to exclude cattle from sensitive areas during the spring and summer months.
A captive breeding programme (more information below) has enabled the project to introduce caterpillars to two sites where historically they were present.
Creating new colonies of butterflies is important because it reduces the chance that unfavorable factors, like climate change with milder wetter winters and summers, could lead to localised extinction. In addition, establishing new colonies ensures that populations are spread across the landscape where interaction with adjacent populations is more likely.
Working with Kew and Durham Botanical Gardens
Marsh violets are the main food plant for the small pearl-bordered fritillary larvae (caterpillars) and planting these plants was necessary to re-store some sites. So the grants funded the propagation of thousands of marsh violet plants using a variety of different methods in partnership with the Royal Botanic Gardens – Kew, London and also the Botanical Gardens in Durham. Teams of volunteers, schools and retirement homes also took up the challenge to help grow plants from seeds. As a result over 10,000 plants were planted.
Nectar plants, such as ragged robin, devils bit-scabious and bugle, important nectar sources for the adult small pearl-bordered fritillary, were bought in as plug plants and planted out to augment this food source.
A captive breeding programme
In 2011, a pregnant female small pearl-bordered fritillary butterfly was captured from the wild and put into a cage where she released her eggs. The eggs in specially created rearing cages developed into larvae in 2012, and the intention was to release the larvae, on to the first re-introduction site, at the pupae stage. However, the very wet winter and spring was catastrophic and few survived.
In the second week of May 2014, 170 caterpillars successfully overwintered from a 2013 hatching, were transplanted at the pre-pupae stage onto the first reintroduction site.
It was a very exciting day and the wait for these caterpillars to emerge as butterflies was an anxious time. It was with great joy that the first butterfly was spotted on the site on the 3rd of June. Butterfly Conservation continued to monitor this site during the summer and counted 20 small pearl butterflies on a single day in July, and volunteers continue to monitor this site.
In the summer of 2014 a new hatch of larvae emerged from eggs laid in captivity and 500 eating machines munched their way through marsh violets at Low Barns. In May 2015, 170 caterpillars were released on to a second re-introduction site, with good numbers of adults counted flying that June.
See this link on the Wildlife Trusts’ website for more information about marsh violets