Yorkshire Status: Scarce and local resident.

Pale Pinion first appeared in the county at Low Bentham in 1996 and can now be found all across Yorkshire. The lockdown ramblings from 2020 go into this in detail and ask a lot of questions. Since the low point of 2020, numbers have increased substantially to 83 records in 2023. These wide fluctuations in numbers may have something to do with cyclic "regulation" from its ichneumon parasitoids.

2020 (CHF): Pale Pinion is a polyphagous woodland moth which historically has been confined to the south and the west of England. In MBGBI in 1983, nearly all records were south-west of a line from the Thames estuary to the Mersey. It was not mentioned at all in Sutton and Beaumont in 1989. Between 1990 and 1996 however it underwent a dramatic and widespread range expansion to the north and east. Current thinking is that south-west Scotland and Cumbria may have been colonised from Northern Ireland and the rest of northern England from moths in north Wales and the west Midlands. The first Yorkshire record was in the west of the county at Low Bentham in 1996 and although there were a few blank years, all five VCs had seen moths by 2004.

The Atlas states "the spread of this woodland moth across eastern and northern Britain during this century has been one of the most substantial of any native species" and the map shows spread as far north as VC92 - South Aberdeenshire. So, there you are, a resounding success story. It's here to stay. But wait, not is all as it seems. Certainly, here in Yorkshire it is having problems. Following the initial colonisation, numbers rose rapidly until 2009 when they stalled and fell. Similar peaks happened in 2014 and 2017 with marked falls between, looking like a cyclical trend. Since 2017 numbers have declined dramatically and in 2020, we had a mere 20 records which makes it essentially the worst year since it first colonised.

The plot thickens when we look at other species from the same genus (Lithophane, meaning "stone-coloured). There are four native species, all of which are relative newcomers to the county, though Grey Shoulder-knot was an uncommon resident in Porritt's time before retreating south. These other three species have all invaded the county in recent times. Grey Shoulder-knot from the south-east, starting at Spurn in 2000 and heading rapidly north and West, Tawny Pinion behaving like Pale Pinion, arriving from the south-west in 1997 and spreading north-east, and Blair's Shoulder-knot arriving from the south-east in 1991 and from the south soon afterwards, before heading north. Each species has moved further north than Yorkshire and looking at the maps in the Atlas, one could be forgiven for getting the impression that populations are healthy and increasing. The situation in Yorkshire however tells a different story. All four are in decline. Tawny Pinion showed peaks in 1999 soon after arrival and in 2007 but numbers have tailed off and there were only four in 2020. Grey Shoulder-knot reached a peak in 2010, a lesser peak in 2018 and has tailed off since. Blair's Shoulder-knot peaked in 1998 and it has been all downhill since.

Another odd observation. Although Blair's Shoulder-knot just flies in the autumn, the other three over-winter as adults and appear again in the spring. Several species of moth over-winter as adults but nearly all of them are equally common in the spring, in fact those where just the females over-winter (Red-green Carpet, Autumn Green Carpet, Brindled Ochre) are much scarcer in spring. Pale Pinion and Tawny Pinion buck the trend by being comparatively scarce in the autumn and much commoner in the spring. Grey Shoulder-knot has equal peaks. Why is this

So, what is happening. What is limiting the populations of these four species? I really don't know. I can't believe it's anything to do with resources, though Tawny Pinion as an ash-feeder might find ash die-back a problem in years to come. Blair's Shoulder-knot isn't suffering through a lack of leylandii cypress. The other two species don't mind what they eat. I can't believe it is anything to do with habitat loss. Is it something to do with climate? The three over-wintering species are suffering the most, and there is some evidence that species over-wintering as adults don't like warm winters as it encourages them out of hibernation to search for food sources which aren't there. Perhaps that is the answer, but the exceptionally cold winters of 2010/11 were followed by a fall in numbers, not a rise. And the "beast from the east" of 2018 wasn't followed by increased numbers. Will they all bounce back after this current cold winter we are having. Does the cyclical nature of the rises and falls mean that it is due to fluctuations in parasitoid numbers? Are there specific parasitoids which just attack Lithophane species. Are these findings mirrored in other parts of the country? Are they in fact commoner than we think and not strongly attracted to light (this seems to be the case particularly for Tawny Pinion and to a lesser extent Pale Pinion, and this might explain low numbers in the autumn)? Why do I always ask so many questions?

Recorded in 108 (54%) of 200 10k Squares. First Recorded in 1996. Last Recorded in 2023. Additional Stats

Exit Recorder