In this post, I'll comment on changes to individual species recorded in my garden in 2021 compared to 2020: I haven't been trapping for long enough to make an extended comparison. With one exception, I am ignoring species that appear on few occasions or in small numbers: their fluctuations are unlikely to be significant.
If I don't apply this "significance" threshold, then random variations become very distracting: for example, a total of 79 species appeared in 2021 that I hadn't found in 2020, but 96 of 2020's species weren't found in 2021. Those 79 species only represent 176 individuals, or fewer than 5% of the total catch for the year.
One of the species that I found on multiple occasions in 2021 having been completely absent in 2020 was Small Square-spot. Common Rustic/Lesser Common Rustic is supposed to be very common, so I will make an exception to my "significance" threshold and report that having had just a handful in 2019 and none in 2020, I managed three individuals in 2021. It is surprisingly uncommon in my neck of the woods; my reduced frequency of trapping in June-August is probably only a part of the reason.
In the opposite sense, species that were absent in 2021 having been significantly present in 2020 include Clepsis consimilana, Hedya pruniana, Sallow, Brown-line Bright-eye and Scarce Footman.
Setaceous Hebrew Character had the biggest increase in absolute numbers (from 90 to 254); Lunar Underwing, Chrysoteuchia culmella and Heart & Dart went in the opposite direction (respectively 847 to 318, 608 to 129 and 447 to 69).
In percentage increase terms, Green Carpet, Garden Carpet and Riband Wave had a good year in 2021. On the other hand, Shuttle-shaped Dart, Large Nutmeg and Brown-spot Pinion were amongst 19 species that had a decline of more than 50%. In addition to Chrysoteuchia culmella mentioned above, other grass moths also fared badly - probably due not only to less trapping when they were flying in 2021, but also to a very local factor. There were changes in the timing of the grazing of the next-door field: unlike the previous year, it was very short during late summer and autumn 2020 when 2021's adults would have been larvae.
In moving on to flight periods, I should emphasise that I only trap once or twice a week, so some timing changes can just be down to different dates when I had the traps out as well as to random chance. However, I do see one change where I would have expected one:
The cooler and wetter spring of 2021 seemed to result in many spring-flying moths first appearing in my traps about three to five weeks later than in the good weather of 2020. For example, Heart and Dart was 26 days later in 2021 and Poplar Grey was 20 days later.
A number of Orthosia species hung around later in 2021: Small Quaker, Clouded Drab, Powdered Quaker and Hebrew Character carried on flying for another 10 to 20 days, generally well into May 2021 although in 2020 they had mostly disappeared by the third week of April. Common Quaker, though, actually disappeared 10 days earlier in 2021.
Dates for autumn-flying moths showed no large or consistent differences between 2020 and 2021.
A total of 65 species (25 macro and 40 micro) joined the garden list in 2021 - my third full, proper year of mothing. The garden (& house) list now stands at 246 macros and 173 micros.
Apart from Nemapogon granella - which is a story on its own - I recorded no unusual or scarce species in VC24: even Clifden Nonpareil eluded me. So - not counting a nice record in France - I am contenting myself with a surprise last evening when the VC66 CMR told me that my photographically-supported record of a Coronet on an otherwise very poor night in late June was only the fourth record for County Durham.
Tim Arnold
Newton Longville, Bucks
Thanks for going to all this trouble, Tim. It makes very interesting reading and your results are fairly well aligned with mine. Setaceous Hebrew Character had a poor year in 2020 but bounced back in 2021 to become one of the best performers of the year here. You mentioned Small Square-spot which is interesting because it seems to be a "boom and bust" species here with its last peaks being in 2008 (649) and 2016 (864). It is currently on the up again after another low point in 2019 (17) so it will be interesting to see if this eight-year cycle continues.
ReplyDeleteI'm sure Clifden Nonpareil will come your way soon enough and the same goes for others who've bemoaned the lack of sightings yet in their gardens! The spread northwards is bound to be a bit patchy but we've had quite a lot of sightings right across north Bucks now. Despite having had it regularly in the garden (no aspen but plenty of other poplars around here), I've yet to track down an adult in nearby Finemere Wood which has plenty of aspen even though a caterpillar was found there in 2018.
Hi Dave. I was clumsy in what I wrote about Clifden Nonpareil. It would have been better to have written that it hadn't returned in 2021 (for the second year in a row) - in fact I caught one in the garden at the end of August in 2019, and another four weeks later about 1 kilometre inside VC32 in Hazelborough Wood near Silverstone. So at least I've seen it, even if not for a couple of years.
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