Portland Moth surveys
The Portland Moth is a very attractive and quite large Noctuid moth, with mottled green colouration on the forewings. It was formerly quite widespread around the coasts of England, Scotland and Wales, but is now much declined and restricted as a breeding species to a relatively small number of known sites in north-west England, north-east England, eastern Scotland and south Wales.
In Scotland the moth appears to have suffered a particularly significant decline in western areas. The Scottish stronghold now appears to be along the coasts of the Moray Firth. The only other recent Scottish records come from Strathspey and in the Tentsmuir area of Fife.
Due to the decline we are encouraging targetted surveys for this rare moth at known and historic locations.
Habitat and ecology
The moth mainly inhabits sand dunes, preferring sparsely-vegetated areas with loose sand. It is also though to occur on river shingles inland along the Spey.
The adult moth is predominantly on the wing in August. It comes to light where it often crawls rather than flies into moth traps. It can also be found nectaring on plants such as Ragwort and heather, and is also attracted to wine ropes and sugar.
The critical part of the life cycle is the larval stage, the main foodplant being Creeping Willow (Salix repens), although the larvae will feed on other dune plants to a lesser extent such as Common Bird’s-foot trefoil (Lotus corniculatus), Common Chickweed (Stellaria media), Marram (Ammophila arenaria), plantains (Plantago spp.) and restharrows (Ononis spp.). It seems that, in Scotland at least, Creeping Willow, which is prostrate and low-growing, is present at all localities and this seems to confirm that this does act as the main foodplant.
The eggs, which are laid in late summer or early autumn, hatch quickly and the larvae overwinter when very small, becoming fully grown the following June. At all stages they spend the day in burrows that they dig in the sand and they then emerge from their burrow at night to feed on the willow. Wherever they are found, it is apparent that the foodplant has open, bare sand around it, presumably so that the larval burrows can be formed adjacent to it.
The map below clearly shows that Portland Moth has a scattered distribution around the coast of Scotland. It also highlights a decline in the number of sites with fewer records post-2005 despite a general increase in moth recording efforts during that time.
Surveys
Due to these declines Portland Moth is a high priority species in our Scottish Conservation Strategy and is also one of the species identified in Butterfly Conservation’s new corporate strategy as part of its first strategic goal to halve the number of threatened species.
We are therefore keen to determine the moth’s current status in Scotland and would like to encourage moth recorders to visit coastal sandy sites, as well as those along the Spey, with Creeping Willow, and particularly any of the dots on the map. We are also hoping to undertake targeted survey days at some of these locations e.g. Tentsmuir and Findhorn Dunes in August.
Light trapping and/or sugaring/wine-roping of suitable locations in the late summer is the most likely way of finding the moth. For further information on where to set light traps or to get involved, please contact Tom Prescott via [email protected]
2023 Surveys update
Surveys were conducted at a number of sites along the Moray Firth with Portland Moth being found at the Fort George and Morrich More MOD ranges. The latter was the first Easter Ross record of the moth since 1940! Creeping Willow was abundant at Morrich More but absent from Fort George which suggests a different foodplant is being used there. The moth was also found again at Tentsmuir, which is the only site where it has been regularly recorded in recent years. Another individual was unexpectedly caught in Strathspey, continuing the suspicion that the moth may be breeding locally on river shingles. Further surveys are planned in 2024, if you'd like to take part please contact Tom Prescott via the above email address.
