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Dark-bordered beauty moth BAP report

Adult male dark bordered beauty moth

What are we trying to achieve?

The Government agreed a Biodiversity Action Plan for this species in 1999. The targets for this plan were revised in 2006 and are as follows:

Ensure the populations of the dark-bordered beauty moth are maintained on all extant sites
Ensure that there are at least six viable populations within the historical range by 2010
Increase the amount of potentially suitable habitat on at least one England site by 10ha and in Scotland by 0.5ha by 2010 (to include any newly discovered sites)

The RSPB is leading the plan jointly with Butterfly Conservation.

What is the RSPB doing to help?

The RSPB has co-funded work in both Scotland and England with Butterfly Conservation, who have implemented the agreed work programme.
Together, we have facilitated workshops to train surveyors in methods and identification.

In North-East Scotland, We helped organise surveys of historic sites to determine the species’ status. In 2001, the moth was found at three sites: two historic sites in Strathspey and Deeside, and a new site, also in Deeside. Detailed observations of caterpillar behaviour and flight times of adults were made in 2002 and the species’ requirement for short (<50cm) aspen suckers became apparent.

The following year, in 2003, habitat management was implemented at all three sites and the area of suitable habitat doubled at the Strathspey site. It was hoped that the moth population would naturally expand into the new area. Larval searches were undertaken to confirm the height of aspen suckers used. For the first time, an egg was discovered in the wild, on the woody base of an aspen sucker, below a mat of grass. It was taken for hand-rearing and its identification was confirmed. The adult was returned to the wild in 2004.

Annual monitoring has continued at all three Scottish sites but numbers of adults remain low. Despite additional habitat creation and the introduction of grazing to one of the Deeside sites, there has been very limited evidence of use of new habitat by the moth. Additional potential sites have been visited but no dark bordered beauty moths have been found.

In England, Butterfly Conservation has surveyed the two previously occupied sites. In 2003, larvae and adults were recorded at the Yorkshire site, but none were found at the Northumberland site. This latter site had become much wetter and was dominated by reed so a programme of reed-cutting was commenced. A larva was found there in 2004, the first since 1999, although there is some doubt as to its identification since another larva found in 2005 proved to be a bordered beauty moth when reared.

Systematic surveys of the Yorkshire site have recorded adults using a large proportion of the total area. A record 82 adults were recorded in July 2005, the highest count for any of the sites. A masters project looked at habitat utilisation at the site.

In 2006:

Continued monitoring at the Strathspey site suggested a lower success than in previous years, with no signs of occupancy in the newly created clearings despite the habitat appearing to be in good condition
At one of the Deeside sites, around five males were seen in an area where the moth was last found 30-40 years ago
A second masters project using mark-recapture techniques to look at dispersal was carried out at the Yorkshire site
The aspen wood at Invertromie on RSPB’s Insh Marshes reserve was thoroughly checked for both caterpillars and adults, with a view to introducing the moth if not already present. None were found despite the habitat appearing to be in excellent condition
A programme of aspen propagation was commenced by the Highland Aspen Group and around 500 suckers have been raised in the first year. The intention is to use these to join up existing stands of aspen in the Highlands
A trial aspen mapping project was undertaken by Scottish Native Woodlands using aerial photos taken from different heights. The technique is effective and funding is being sought to extend the project
Forest Research used the photos for an aspen modelling project. Dark bordered beauty moths are one of the species being modelled

Summary of progress

The status of dark-bordered beauty moth is still very vulnerable but is improving. It is present at three Scottish sites and one in England.

Habitat observations suggest that in Scotland, the dark bordered beauty moth is very dependent on new low growth of aspen from suckers and is lost when areas become too tall. Management recommendations are being implemented at the three Scottish sites and new habitat has been created, but despite appearing suitable, this has had limited use by the moth so far.

In England, the moth lives in more open habitat and feeds mainly on creeping willow, Salix repens. Two Masters projects examining its habitat utilisation and dispersal have found that the moth is largely sedentary with a small sample of males moving an average of 15m and females 3m.

Has our work been effective?

We have determined the species’ status and have started to investigate its ecology. We are increasing the amount of suitable habitat at the known sites, and attempting to link areas in Scotland. Given the species limited mobility, it could be many years before the population expands, unless assisted through translocation.

What do we plan to do next?

Create 2-3 more clearings at the Strathspey site to open up further areas for aspen regeneration
At an adjacent conifer plantation, now entered into a Scottish Forestry Grant Scheme, create clearings by felling areas of Silver Fir and plant them up with aspen of local provenance
Control scrub and rank vegetation at the first Deeside site
Coppice suckers at the second Deeside site
Consider potential translocation to the RSPB’s Insh Marshes reserve
Continue to increase the area of creeping willow at the Yorkshire site
Continue monitoring at known sites

What are the constraints to fully achieving the targets?

Poor understanding of the autecology, especially at willow sites
Loss of suitable habitat due to neglect or loss of aspen woodland
Population isolation limiting opportunities for natural re-colonisation of suitable habitat