More than 300 eggs of the rare brown hairstreak butterfly have been discovered near Llandeilo in south-west Wales this winter, marking a record count and a 50% increase on the previous year. The recovery follows a decade of decline, attributed to landowners halting annual flailing of hedges.
The brown hairstreak lays its eggs on blackthorn in summer, but mechanical cutting of hedges each autumn destroyed thousands of eggs unknowingly. Conservationists persuaded landowners to adopt a gentler rotation, leaving sections uncut for up to three years, allowing more eggs to survive winter.
Volunteers for Butterfly Conservation counted 276 eggs on the north verge of the A40 west of Llandeilo and 117 on the south verge – both record counts. Nearby hedgerows also saw increases after sympathetic management, including planting new blackthorn bushes.
The upturn comes after the butterfly almost disappeared from the Tywi valley due to increased flailing. In 2021, a small remnant population was found, prompting annual egg counts and collaboration with the National Trust and the South Wales Trunk Road Agent to protect hedgerows.
In contrast, a nearby group of fields where hedgerows were flailed saw egg counts drop from an average of 60 to just four this winter. Richard Smith, a volunteer for Butterfly Conservation, expressed excitement at the signs of recovery, noting that the Welsh government's new sustainable farming scheme requires avoidance of annual flailing.
Dan Hoare, director of nature recovery at Butterfly Conservation, urged landowners to cut hedges every two to three years instead of annually, emphasising that hedgerows are vital ecological infrastructure and that the brown hairstreak is an indicator of getting management right.
