Allerthorpe
Common
Managed by Forestry England and YWT
Site Details
Recorders: Steve and Penny Relf & Fiona Parkinson Length 2867m Walk Time 1 hour Altitude 18m
Allerthorpe Common lies on river and lake sands, which were deposited during the last glacial period 10,000 years ago. The soils are acidic and support a surprising range of habitats for such a small pocket of lowland heath - wet heath, dry heath, acid grassland, woodland, scrub and open water. Ling heather, tormentil, sheep's fescue and wavy hair-grass grow on the drier areas of the site. Cross-leaved heath and purple moor grass grow in the damper areas. Patches of gorse and areas of mature birch and willow woodland. The Transect route covers a good many of these habitats
Sections:
Section 1 in the wood is prefered by Brimstone and Speckled wood . Gatekeeper, Large Skippers and Meadow Browns with Peacock prefer prefer S4 +S5 while Ringlets very much favour S6
The section counts are shown opposite
2024 Results
After a warm winter April turned cold, very wet and dull and everything just about stopped and it was near impossible to transect walk all month. By May there were already losses among our spring species being down a third in numbers. June brought Arctic winds, a complete reversal of the Hot June of 2023 when nine species reached all time highs here and across the UK. For the first two weeks of this June temperatures were 8’C cooler than in 2023 around a frigid 9’C with only 5 good days of sun at the end of the month. The first three weeks of July had the same theme of cool and damp with 5 warm sunny days at the end. Transect walking for many was very difficult. The persistence of the cold and damp over such a long period had a devastating effect with numerically two thirds of our butterflies in the critical later stages of their development; mortality was very high. It was also one of the longest June ‘Lulls’ lasting from late May to the beginning of July. When the main flight season did arrive it was slow to build up and there was no usual peak. Better weather in August helped save the second generation and very unusually numbers actually went up at the start of September.
Losers
For many species it was a triple whammy after the heat and droughts of the previous 2 years and last July’s poor flight period this year made it a perfect storm. Overall, annual numbers were down 41% against the average and 45% down on last year. Half our species were down more than 50% and a quarter down more than 70%. The Lycaenids, Vannesids and the Fritillaries were amongst the worst affected. Many transect walkers did not see a single Common Blue, Small Copper, Holly Blue, or Brown Argus until late into their 2nd broods.. Four of our long term declining species Common Blue, Small Heath, Small Skipper and Green-veined White had their worst year ever recorded.
The Winners and less bad losers
Northern Brown Argus had an exceptional year up near 50% Other species bucking the trend were Brimstone and Marbled White. The damp loving Ringlet on many limestone/dry sites were up a half while on most wet sites they fell by a half. However if it wasn’t for Ringlet holding up the overall numerical losses, this year would have been significantly worse. It often happens when Meadow Brown has a very poor year, like this one, Ringlet does proportionally better, and vice versa in a warm year.
It has all happened before… many times.
It was our worst year since 2016 but nearly as bad as 2009 when numbers were down 50%. 2024 comes after a run of 6 relatively good years since 2018 along with rapidly rising temperatures including 2 of our hottest summers which were followed by two of our best butterfly years in 2019 and 2023. It is likely 2024 was a blip
Allerthorpe did rather better that most of the county and in the top ten largely due to the Ringlet having a much better year and Meadow Brown only suffering light losses. Peacock as on most sites showed an significant improvemnt on last year. The lycaenids took a bigger hammering here more than other places. Liek teh Browns the skippers did relatively well compared to much bigger losses elwsewhere. We might suspect that the recovery in both the grassland browns and skippers is due to te habsence of drought on this sandy sight.
2023 Results
County wide 2023 results reflect the worse affects of the 2022 and 2023 spring drought with Small Tortoiseshell and peacock nearly halved against their 5 year average. Red Admiral arriving in force in July took advantage of soft nettle growth of teh rains and had their best year ever. Drought sensitive species on thin soils were badly hit, particularly Dark -green Fritillary and Northern Brown Argus but also Ringlet, Green-viened White and Small Heath. Less drought affected species along with the hottest June on record built even more on gains last year leading to Comma, Holly Blue and most Browns having a fantastic year reaching all time highs. A increase of 9% ioverall was mostly due to sheer numbers of Meadow Browns and Gatekeepers ment 2023 nearly pipped 2014 as best year in modern times. Most noticeable was the large differeces between mositure retaining mineral soils of the valleys and thin, dry limestone or sandy soils. A large number of damp grassland, hedgerow and woodland dominated sites benefitted hugely with 3 sites seeing more than 50% increase . A smaller number of thin, chalky, sandy or craggy sites did badly some down up to 25%.
2022 Results
The Skippers follow the county trend downwards as do the whites with small white being the exception with a large increase over last year. In this largely woodland site Brimstone is exceptionaly abundant and third most common species and had another good year simalar to last. Other species generally follow the county trend with teh Vannesids overwintering well but , other than Comma, halving with the second generation largely absent , while, cCmma had a really good summer brood. Speckled Wood as elsewhere were abundant and well up on last year. The browns followed almost exactly other county sites with Ringlet well up and Meadow Brown a tad down. Overall a bit down on last year which was teh case in other woodland sites nearby mostly because of the Vanessids collapse.