Thorpe Marsh YWT
Doncaster
Site Details
Recorders: Michael Townsend with Julie+Nathan Leyland, Janet and Jeremy Mansell Altitude 15m Distance 3550m Walk Time=1.5hrs
The land here was owned by the power station that used to stand just to the east, and has been managed by Yorkshire Wildlife Trust since before the power station closed. There is an old railway embankment that bisects the site, and the East Coast Mainline runs along the western edge. The Ea Beck is to the south. The island of land between all these areas meant it was never intensively farmed, and ridge and furrow landforms can still be seen in the fields. The land was purchased by the Central Electricity Generating Board in the 1960s for tipping fly ash on a large site to the east and beyond that the cooling towers of the old power station still stand. This has meant that a great mix of plant species have flourished. Its pastures lined with hedgerows, ponds, lakes and small woodlands have varied habitats. management is by Cattle grazing and an occasional mow in August and September. Scrub encroachment is dealt with by hand when in small areas and foot paths kept strimmed. Purple Hairstreaks are seen amongst the mature oaks some years.
Sections:
The very noticeable change is 2019 and 2020 in the rapid increase in particularly . Now section 4+5 is responding similarly.
S1 and S6 woodland is prefered by Speckled Wood pr
S7 is best for Common Blue, Small Copper, Small Skipper, Hedge Brown, Small Skipper and Ringlet and Meadow Brown
S7and S8 is prefered by Comma's and Peacocks
2024 results
Countywide, 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
Thorpe Marsh results were a tad worse than the county average of -41% but not similar to other similar damper lowland sites. As always at this site Meadow Brown accounts for a very high percentage of any changes and it has been a very poor year for them. Ringlet increased by nearly double which is similar to other sites . Large Skipper, Brimstone and Orange tip all increased favouring the damper conditions. The real losers were among the Lycaenids and Vanessids. 2024 was very similar to the disastrous years of 2012 and 2009 for Small Tortoiseshell. peacock in contrast quadrupled on last year with a strong recovery as they did in most sites.
2023 results
County wide 2023 results reflect the 2022 Heat and drought with Small Tortoiseshell and Peacock nearly halved for the second year against their 5 year average. Red Admiral arrived in force in July and took advantage of soft nettle growth of the 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, Brimstone, Holly Blue and most Browns having a fantastic year reaching all time highs. A increase of 9% overall 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 moisiture 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%.
Thorpe Marsh is a tad down and although it follows the county trends seems to have suffered a somewhat more with the affects of heat and drought of 2022. In common with elsewhere Gatekeeper and Meadow Brown well up on last year as is Speckled Wood. Comma had a great 2023 reaching an all time county high along with Red Admiral and Brimstone. Great to seee Small Skipper bounce back with a 3 fold improvement along with Small Copper, Brown Argus and Common Blue; we have this seen elsewhere on dry sites. Its a great pity both Small Tortoiseshell and Peacock are universally still having a bad time here as in many parts of the Vale of York it has continued downwards for 2 years; although in the hills Peacock has come back quickly after hitting a low last year. Hopefully they wil bounce back after the wet/cooler summer. Drought sensitive Ringlet and Green Viened White are down as they are across the county . Great to see the Small Heath trying to come back and Dingy skipper had a very good year. Both indicate more bare ground/finer grasses and a change in the habitats.
2022 results
A poor year particularly for the skippers and whites and only the Brown Argus amongst the blues reflected the countywide boom in this species. The vanessids were also badly effected by the drought with most species halved apart from Comma which nearly held its own. Countywide Comma boomed universally . Speckled Wood although up on last year was down on the average while across the county it had a good year. Browns were all down which is in contrast to the county where they did well. Gatekeeper was the least down and actually boomed across most of the county. The graphs below show the long term trends in species with some interesting patterns, but importantly the overall abundance of species is up by about 8% per decade. It is interesting to see how that increase is changing with time with big winners like Meadow Brown up 12% and big losers like Gatekeeper 5% of total species per decade. There has also been rapid decline in Small Copper which appears to be county wide but rapid gains for Orange tip doubling and Brimstone tripling which is in part reflected in the county
2021 results
Although one of the poorest years for some time being 11% below the 5 year average there are interesting trends.
It is also nice to see Dingy Skipper and Small Heath return even if wanderers
The main factor is the drop in Meadow Brown down nearly 1000 compared to last year but still fractionally above the average. There is a good deal of recovery in numbers of the other browns with Ringlet bouncing back to near normal after the massive loss in 2020. Gatekeeper also came back while on almost all other sites they had a really good year. Your left wondering how the flooding of 2020 is stil working its way out.
Small Tortoiseshell continued to boom as it has on most sites. Orange Tip stays low and although it boomed on most sites but not here. The whites had a poor season particularly Small White as elsewhere.
2020 results
Although numbers have increased significantly in 2020 it is dominated by Meadow Brown while many other species had big losses. Ringlets were well down but does require a damper environment than Meadow Brown and following the heat of 2019 and drought of spring 2020 could easily be responsible. However the Whites and Skippers are also down along with Orange Tip Again in common with many other transects. It is Common Blue that has suffered the most along with Brown Argus, Small Copper.Dingy Skipper was not recorded this year. In line with many other transects Small tortoiseshell saw an increase.
Michael Townsend summarises the year:
If one discounts the high numbers of Meadow Browns, 2020 was overall one of the worst three of the nineteen transect years. Only 2007 and 2008 were as bad. 2007 was the year of severe local flooding that also poured on to the nature reserve, affecting butterflies and forcing the missing of three weeks counts including the normal peak for Meadow Browns and Ringlets. The effects of the flooding probably led to reduced numbers in 2008.
2020, therefore, was an unusually poor year for most species.
Meadow Browns had easily their second-best year, only 2013 being better. The only other species with better than average years were Brimstone (fourth-best but still with low numbers), Small White (also fourth-best) and Peacock (equal fourth best).
Average years were had by Red Admirals, Orange Tips (but well down on 2018 and 2019) and Small Tortoiseshells.
Worse than average years were had by Small Skippers (worst since 2011), Large Skippers (worst since 2013), Large White (equal fourth-worst), Green-veined White (sixth-worst), Small Copper (equal fifth-worst), Common Blue (well down on the previous three years), Comma (fourth-worst), Speckled Wood (second-worst, only 2007 was worse), Gatekeeper (second-worst, only 2007 was worse) and Ringlet (third-worst, ahead of only 2007 and 2008).