Thorpe Marsh  YWT


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.


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 

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.

Transect reports 2020

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).