- The Dark Bordered Beauty moth is one of the UK’s rarest moth species and can only be found at a few sites in Scotland and a single location in England
- RSPB Insh Marshes nature reserve has had the best year ever for recording the moths with a population of 176, a significant increase from 81 in 2022
- By managing the aspen woodland, where the Dark Bordered Beauty can be found, the reserve team have created suitable habitat for the moths to flourish
The Dark Bordered Beauty is one of the UK’s rarest moth species but has been reported in record numbers at RSPB Insh Marshes in Scotland this year with a population index of 176. This is a significant increase from the reserve’s previous best record of 81 individuals in 2022. Whilst the Dark Bordered Beauty is still a Priority Species on the UK Biodiversity Action Plan, these numbers provide hope for the species.
This attractive yellow-orange moth, with characteristic dark wing borders, can only be found at a few sites in Scotland and a single undisclosed location in England. They are typically associated with aspen woodland in Scotland, which is itself a threatened habitat, and has declined over recent years as a result of deforestation and over-grazing.
Aspens rarely flower or set seed and rely upon suckering from tree roots to spread – these suckers act as a primary food source for Dark Bordered Beauty moth caterpillars at RSPB Insh Marshes. To improve suitable habitat for the rare species, the reserve team have implemented conservation efforts to support aspen woodland regeneration.
As Julie Ellis, the warden at RSPB Insh Marshes, explains: “On the Insh Marshes reserve, we have ensured that there are areas available for the aspen to spread into by suckering. We have removed birch saplings in some areas, where they might out compete aspen suckers by keeping them in the shade, and have even cut aspen suckers to the height apparently used by caterpillars. Ideally, in the future, the aspen woodland boundary can ebb and flow naturally so that less intensive habitat management is required.”
The combination of aspen woodland regeneration and reducing grazing pressure in and around the woodland, has led to the record number of Dark Bordered Beauty moths at Insh Marshes – demonstrating how effective conservation efforts can support moth populations.
Intensive monitoring of the Dark Bordered Beauty this summer resulted in more than twice as many moths caught than in previous years and was undertaken by a single member of staff during their sabbatical at RSPB Insh Marshes.
For one month, Mick A’Court, assistant warden at the RSPB’s Buckenham and Cantley Marshes and Sutton Fen reserves, set up moth traps in different areas of aspen woodland at night during the Dark Bordered Beauty flying season. Trapped moths were identified, counted and released in the morning – a total of 12,058 moths of 212 species were trapped over the four-week monitoring period.
Although initial numbers of Dark Bordered Beauty counted were low, they soon ramped up to never-before-seen levels with 34 moths (33 males and 1 female) counted in a single trap, a notable increase from the previous year’s record of 13.
On his efforts, Mick says:“It was astonishing to find 33 males and 1 female in a single trap. This is far in excess of anything caught in a single trap before. Quite why this apparent irruption in numbers occurred at the end of the moth’s flight season is unclear, but the final count of 176 moths does demonstrate that there is a good population at Insh Marshes.”
A captive breeding programme of Dark Bordered Beauty moths is currently being undertaken by the Royal Zoological Society of Scotland at Highland Wildlife Park, with the stock used originating from Insh Marshes. The programme provides eggs, larvae and adult moths for introduction into a small number of suitable sites in an attempt to start new populations in other areas of Scotland.
By combining vital habitat restoration and management, alongside the innovative captive breeding programme, the outlook hints at a brighter future for this rare moth.
ENDS
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