Rare butterfly numbers on the rise

Record numbers of the rare and exotic Swallowtail Butterfly have been sighted in the Broads this summer – the first increase in nearly 100 years. The Swallowtail, Britain’s largest butterfly, draws enthusiasts from all over the UK to sites including the How Hill National Nature Reserve, Hickling Broad and Strumpshaw Fen from late May until early July and a rare second brood has extended the Swallowtail season into August.

The Swallowtail has a wingspan of up to 9 cm, predominantly yellow with dramatic black markings and scalloped edging at the bottom. Swallowtails were once widespread across the UK but they are now found only in the Broads and at Wicken Fen in Cambridgeshire. The rise is thought to be due to successful fen management over the last 15 years which has resulted in an increase in milk parsley which provides food for the Swallowtail caterpillars. Numbers declined sharply in the 1920s when the demand for thatch and marsh hay for London cab horses diminished – bringing about a decline in the reed- and sedge-cutting industry. This left the marshes overgrown and neglected, and by the 1980s much of the open fen had been lost and milk parsley could not survive in the scrub. This meant there was limited food for the caterpillars.

In the late 90s the Broads Authority, a member of the National Park family, set in motion a fen management strategy and together with the Norfolk and Suffolk Wildlife Trusts, RSPB, Natural England, National Trust and private landowners began harvesting the fen and clearing scrub which had been invading the fen since the Second World War. Government funding from agri-environment schemes to landowners has financed  much of the work.

For more on visiting the Broads, please see www.broads-authority.gov.uk