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

Pexton Bank sees a significant decrease in numbers this year and worryingly a complete absence of Dark Green Fritillary after its collapse last year in the heat. The Small Pearls also seem to have suffered badly too on the steep sloping chalkland part wooded bank.  As a results almost all species lost out  apart from Meadow Brown, Speckled Wood, Comma Red Admiral and Brimstone all of whom boomed across the county. 

An above average year but this site in contrast to most is steady or showing a slow decline in numbers with the last peak in the universally good year of 2019.

Small Skipper is on a long term decline here as are Large skipper.  Dingy Skipper levels held up well but were down elsewhere. All the Whites did well apart from Large.  Small Copper after returning for a few years disappeared.  A duke of burgundy was seen which is a first for many years and generally the dukes had a better year with some dispersal.  Brown Argus and the other blues were down  in the drought as  they were at next door Ellerburn Bank.  All the Vanessids had a very poor year with many not being seen after the end of June with enforced hibernation in the heat. Small Pearl-bordered Fritillary had a much better year trebling on last year but still this species appears to be on the decline. Dark green had a very poor year down to a tenth of the average  although it was down on most sites.  Wall is showing signs of a slow recovery after reappearing in number in 2018 it was however rather down thsi year.  Speckled wood remained average whiel marbled white was somewhat down. The browns accounted for most of thsi years gains for teh site compensating for all the losses.

2021 was a much better year than 2020 but not exceptional like 2019.

Brimstone and  Orange Tip saw increases as in many Yorkshire transects.  Dingy Skipper saw an increase to a new  high.  Large Skipper returned in better numbers and there is obvious signs of recovery after the spring 2020 severe drought in many species . Brown Argus, Common Blue and Small Copper  had some of their best counts . Comma and Red Admiral did particularly poorly as they did almost everywhere while Dark-green Fritillary had its best year. Speckled Wood is stil recovering while  Marbled White boomed as it did elsewhere and Wall did well

A poor year compared to recently particularly amongst our grassland species with Wall brown not appearing, Skippers apear to be in a steady decline. teh migrant Vannesids were wel down as they were on many sites along with large whites  but unusually Peacocks had a poor year as well. Fritillaries werea littel down while Dingy skipper looks fairly steady.  Duke of Burgundy was not seen. See comaprisons below:

The following adjustments were applied to compensate for missing beginning of the season: Dingy +5, Large White +1, GVW +7, Brown Argus +1, Red Admiral+2,  Small Pearl +2, DGF +5,  Peacock +5,  Small Tort +1