This year started slowly, and never recovered.  The late frosts into April and May had a severe effect, with much of the gorse obviously dying back.  This was followed by a wet June, and a period where hot weather alternated with heavy downpours.  By the time the summer settled in July, it was clear that butterflies were emerging late, and in smaller numbers than usual.  By contrast, 2021 saw the best September results, but this was too little, too late, for most species.  The annual total of 1,822 butterflies seen made 2021 the fifth of the seven years so far, the worst since 2017, and 34% down on last year.  Nine of the ten commonest species this year decreased in number from last year.  A total of 23 different species were seen, the same number as last year.

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The two commonest species, Gatekeeper and Silver-Studded Blue, both saw declines of over 30%, but what is perhaps more worrying is another 30% decline in Meadow Brown, which had its poorest year yet, and the first year that fewer than 100 individuals were seen.  The poor Spring doubtless affected Brimstone numbers, down by over 50%, with Large White and Green-veined White also decreasing by over 60%.  By contrast, Small White improved by 40%, and Small Copper also had a good year, increasing by over 20%, and benefiting from a warm, dry September.  It was also a good year for Grayling, with a record 32 sightings, again lasting well into September.

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The decline of the woodland species is particularly worrying, as it suggests that the management of the Inclosure may be failing our butterflies.  When Forestry England contractors selectively felled some of the pines in Alderhill in the Winter of 2018, I anticipated an increase in biodiversity caused by the extra light and clearings created.  Not only is there no evidence of this having happened, numbers of previously seen species continue to fall to alarming levels.  In 2021, no Ringlet or Small Skipper were seen (the first year that either of these species has not been found in the wooded area of the route).  In addition, Silver-washed Fritillary had its worst year ever (two seen, compared to at least 10 in all previous years), and the 22 Speckled Wood seen was also the lowest annual total for that species.

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The highlight of the year happened on Week 16 (23rd July), when a single male Purple Hairstreak was seen (and stayed long enough to photograph!) under an oak tree along the green ride separating Alderhill and Sloden Inclosures (Section 3 of the route).  This elusive small canopy-dwelling butterfly became the 31st different species seen on site.  There was a brief glimpse in late August of a small, golden butterfly heading into the canopy nearby, which may (or may not) have been a Brown Hairstreak, but it was too distant to be sure about, so that one remains on the one-that-got-away list.  I will check the nearby blackthorn scrub for eggs over the winter, to see if there is evidence that this species is around.