Butterflies Thrive at Carymoor in 2020

Butterflies Thrive at Carymoor in 2020

What an extraordinary year 2020 has been for our butterflies. Whilst Butterfly Conservation's Big Butterfly Count (BBC) recorded a fall in the average number of butterflies per count of 34% compared with 2019, and the lowest average number of butterflies overall since the Count began 11 years ago, here at Carymoor we had the highest average number of butterflies since 2015 for those weeks when it was possible to walk the transects. The table below shows the weeks in which the transects were walked in 2020 and the number of butterflies counted for each of those weeks since this data set began in 2013; and the average number of butterflies counted per walk. It reminds us what a good year 2014 was and how much the numbers can vary in the same week of different years, depending not only on conditions during the flight period but also to some extent on the weather conditions in the previous winter and early spring, which affects when the butterflies emerge. It also shows that, since a trough in 2017, numbers have been climbing back steadily. Interestingly, the total count for the limited season of 2020 was higher than for those for the full seasons of each of the four preceding years. 

Of course, the BBC records numbers of those butterflies found in the wider countryside and does not include the habitat specialists such as Grizzled and Dingy Skippers, which are included in the Carymoor figures. But despite the abundance of butterflies in 2020 the sad fact remains that of the 25 species recorded – one fewer than 2019 – 12 declined in abundance, 11 increased, and one was stable; the Essex Skipper was counted together with the Small Skipper, making up the missing 25^th species.

Perhaps the most extraordinary thing about 2020 was the complete absence of Painted Ladies. 2019 was a Painted Lady year, which occur roughly every 10 years, the previous one being 2009, when 92 of these migrants from the continent were recorded; in 2020 not a single one was recorded at Carymoor and throughout the country there was a scarcity of them; but they will be back in force – around 2029!  Of the other two common migrants 4 Clouded Yellows were recorded, more than in the previous year but nothing like 2013 and 2014 when 60 and 45 were recorded respectively.  Red Admirals, some of which may be home grown, did well, increasing by 36% over the previous year.

The first count was on 20 May (in week 8), by which time the Orange Tip flight season was virtually over and only one was recorded, so we don't know how they fared this year, but up to 64 have been recorded in the past. Similarly, the beginning of the flight period for Grizzled and Dingy Skippers was missed but nevertheless, the Grizzled recorded its second highest numbers with an increase of 66%; but the Dingy Skipper was down by 45%, although there was a small second brood, which suggests that some in the early flight period were missed and the overall numbers may well have been higher.

Once again, the most abundant butterfly was the Meadow Brown (pictured) with 802 records (an increase of 36%), a position it has held every year except one; but the winner in terms of percentage increase was the Large White with 136%, which put it in 8^th place in terms of abundance. In the BBC the Large White was first in abundance with an increase of 44% and the Meadow Brown was 5^th in abundance and down 2%. It is also interesting that at Carymoor the Peacock had a very good year, up 91% on 2019 and 9^th in abundance, whereas in the BBC it was down 42% but in 4^th place in terms of abundance. The Holly Blue also had a good year; and it was very pleasing to see the Brown Hairstreak back on the list with 5 records, after an absence last year.

On the debit side of the ledger, too many species suffered a decline, in 3 cases of more than 50%.  Brimstone was down by 57%, but this is undoubtedly due in part to missing the early part of the flight season when Brimstones are one of the first butterflies to emerge from hibernation as one of the harbingers of spring. Common Blue numbers fluctuate wildly and in 2020 were down by 65%, to their second lowest level since 2013, having had a very disappointing second brood; hopefully they will bounce back again in 2021. Small Copper numbers also vary considerably and in 2020 were down by 51% to just 15. However, in 2016 only one was recorded but in 2018 the number increased to a record of 43. Speckled Woods were down by 24% but again this may be partly due to missing the early weeks of the season. The Small Tortoiseshell always causes concern but this year just about held its own, with 43 recorded; but the overall trend for this species, once one of our commonest butterflies, remains down and it is hard to believe that in 2014 973 were recorded, more than any other species apart from the combined Small/Essex Skipper tally of 1,286, the highest species total in any year since 2013.  Finally, it is sad to record that no Small Blue has been seen since 8 were recorded in 2016.

Numbers of each species vary from year to year but it is longer term trends that are the important indicator of the state of our butterflies – and indeed other wildlife, too. There is still a long way to go to get back to the numbers of even a few years ago –  in the 2014 season 5784 butterflies were recorded and since then the trend has been down; the 2020 figure, admittedly for a curtailed season, shows a drop of more than half in just 6 years. The need to manage our environment for the benefit of wildlife is as important now as ever.  Of course, it is very pleasing that the numbers of butterflies have risen over the last four years and it is very much to be hoped that this trend continues; this is why sanctuaries like Carymoor are so vital.