The Marsh Fritillary, once common across the UK and Ireland but severely reduced during the last century, has enjoyed a strong resurgence in Northern Ireland thanks to warm weather and long-term conservation work.
Butterfly Conservation reports major increases in the number of silken caterpillar nests found during recent surveys. While favourable weather helped, the charity stresses that habitat restoration is the real key to recovery. The species relies on a single plant—Devil’s-bit Scabious—found in grazed grasslands and heathlands, many of which were lost due to modern farming practices.
Conservation manager Rose Cremin has worked closely with farmers to ensure land is managed in a way that supports the butterfly’s needs. This includes adjusting grazing practices and maintaining ideal grass heights for egg-laying.
Each autumn, volunteers count the larval webs that caterpillars build around their food plant. The results this year were dramatic: one site saw nest numbers jump from 24 to 53, another from 24 to 139, and a third from 5 to 27.
The Marsh Fritillary produces only one brood a year, making it particularly vulnerable to habitat loss or food shortages. Its distribution fell by 43% between 1985 and 2019, and overall UK butterfly populations continue to face long-term decline.
Cremin says the latest increases show that years of work by farmers, volunteers and landowners are beginning to pay off—but sustained habitat management remains essential for the species’ future.
