Butterflies bounce back

Butterflies bounce back

23 Mar 2020

Marbled White. Liz Cutting

In their best year since 1997, just over half of UK butterfly species monitored showed higher population levels in 2019 compared with 2018, making it the eighth best year out of the 44 year series.

Butterflies most likely benefited from an unusually warm and wet summer, which resulted in a strong emergence of adults and successful development of the immature stages preceding this emergence. This boost should further help priority species in longer-term declines, some of which (e,g, Brown Hairstreak, Dingy Skipper, Large Heath, Marsh Fritillary, Small Blue and the Silver-spotted Skipper) have benefitted from intensive conservation management of breeding habitat.

Summer flying species which benefitted included the Marbled White, which had its best year in the series (1997-2019) with annual abundance up by 66%, Ringlet (second best year in the series, up by 23%), Dark Green Fritillary (third best year, up 51%), and Meadow Brown (fifth best, up 38%). The rare Lulworth Skipper, restricted to the Dorset coast which has been in freefall in recent years rallied with its abundance up by a whopping 138%.

The greatest increase since 2018 was in numbers of Painted Lady, by about 20-fold. Red Admiral also had a very good year, with abundance almost three times higher than in 2018.

It wasn’t all good news for summer flying butterflies though as between 2018 and 2019the Common Blue dropped in abundance by 54%, Adonis Blue by 40%, Green-veined White by 43% and Large White by 40% with all four species having below-average years. Of particular concern is the rare Heath Fritillary, which is restricted to a tiny number of sites in southern England. This butterfly saw its annual abundance drop by 34% since 2018. This further drop raises fears for the long-term future of the butterfly whose numbers have fallen by a shocking 91% since the 1970s.

It is with thanks to the BTO/JNCC/RSPB Breeding Bird Survey volunteers, who also collect butterfly observations on their BBS squares of the Wider Countryside Butterfly Survey - which feeds into the UKBMS results - that we are able to produce an up-to-date picture of the health of butterfly populations, as illustrated in the UKBMS results.

UKBMS is led by Butterfly Conservation, the Centre for Ecology & Hydrology (CEH), British Trust for Ornithology (BTO) and Joint Nature Conservation Committee (JNCC).

View the full results, or learn more about participating in Butterfly Monitoring Scheme via the Breeding Bird Survey.

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