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 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.

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

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.

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).