big butterfly count 2018 results

The joint warmest summer on record combined with excellent media coverage led to record-breaking numbers of people taking part in big butterfly count 2018. For the second year running, the number of participants increased by two-thirds and the number of completed counts also rose by over half. An incredible 100,246 people took part in 2018, undertaking 97,133 counts. Butterfly Conservation would like to extend a huge thank you to everyone who took part and helped to make the 2018 count the largest citizen science insect survey in the world.

Given the long, hot sunny spell leading up to big butterfly count 2018, conditions that are ideal for butterflies, we expected record-breaking numbers of sightings, alongside the fantastic levels of participation. Almost 1 million (964,480 to be precise) of the 19 target species (17 butterflies and two day-flying moths) were recorded during the official big butterfly count period of 20 July - 12 August 2018.

Yet despite these impressive numbers, participants generally did not experience a butterfly bonanza. On average, just over 11 individuals of the target species were seen per 15-minute count, only slightly higher than the 2017 average (11.2 in 2018 compared with 10.9 in 2017), which was the lowest since big butterfly count began in 2010.

The disappointing number of individuals seen by participants is probably not a fair reflection on the population levels of the UK's common butterflies and moths during the summer. The warm weather from April onwards led to many species starting their flight periods early in 2018 and, as a result, some of the abundant single-brooded species such as Meadow Brown, Ringlet, Six-spot Burnet and Marbled White were already past their peak in numbers by the time big butterfly count 2018 started.

Wondrous whites and bountiful blues

The whites were the stand-out winners of big butterfly count 2018. The total abundance of Small White, Large White and Green-veined White made up 55% of all the target species counted in the 2018 event. Small White was the most abundant of all the target species, the third time that this species has topped the big butterfly count charts and the butterfly had its second highest average number per count (after 2013). Large White came second overall and also had its best year (in terms of average numbers per count) since 2013. Numbers of both species were more than double that seen in big butterfly count 2017. Green-veined White was up 78% on the same period in 2017.

The two blue butterflies included in big butterfly count also had a bumper summer. Holly Blue had its best ever big butterfly count and achieved its highest placing in the rankings (12th), while Common Blue came 6th overall and had its highest numbers per count since 2010 (the first year of big butterfly count). Holly Blue counts were up 122% on summer 2017 and Common Blue numbers increased by 51% year on year.

The Silver Y moth also had a good summer, with its highest number per count since 2013 and a threefold increase on 2017. Interestingly, this was the only one of the three migrant big butterfly count target species that did well in the summer of 2018 (the others being Red Admiral, which decreased substantially, and Painted Lady, which showed little change).

Small Tortoiseshell slump

Not all species thrived during the hot summer of 2018. The Small Tortoiseshell, which has lost three-quarters of its UK population since the 1970s, suffered its worst big butterfly count on record, worse even than in the wash-out summer of 2012. Small Tortoiseshell numbers were down by a third compared to the same period in 2017 across the UK as a whole, although this drop was driven by counts in England, while numbers in Wales and Northern Ireland remained stable and the species actually increased in Scotland. Worryingly, the causes of the ongoing long-term decline of this beautiful butterfly are still unclear.

Two butterflies that did extremely well in 2017 were, surprisingly, among the biggest losers in big butterfly count 2018. The Red Admiral was 73% down on the high numbers recorded in 2017, when it came 2nd overall, and finished in 9th place recording its lowest average number per count since 2012. After such a good year and with long periods of stable, summer weather this year, we might have expected numbers to rise further in 2018, but the extremely cold spells earlier in the year may have killed over overwintering Red Admirals and their offspring and, for unknown reasons, the butterfly does not seem to have migrated to the UK in large numbers during the spring and early summer. The Comma also fared relatively badly, after a good 2017, with numbers down 40% year on year. Unlike the Small Tortoiseshell, both these species have fared well in the UK since the 1970s, so these dips are not of serious concern.

The Gatekeeper also decreased, with numbers down 54% from the levels seen in the same period in 2017. Although still abundant, and finishing 3rd in big butterfly count 2018, the Gatekeeper had its worst year since the survey began in 2010 and has undergone a long-term decline in numbers in Britain since the 1970s.

Other species that showed large year on year declines in summer 2018, such as Marbled White, Ringlet, Six-spot Burnet and Meadow Brown had emerged early in the very warm spring/summer, well before big butterfly count commenced. Such effects are inevitable for a short, ‘snap-shot’ survey like big butterfly count, but does not lessen the importance of the event. Butterfly Conservation scientists have shown that such effects can be corrected retrospectively to ensure that big butterfly count data can make a meaningful, long-term contribution to assessing the state of the UK’s common butterflies.

The 2018 results for all 19 of the big butterfly count target butterfly and moth species are shown below:



% change from 2017


Small White




Large White












Meadow Brown




Common Blue




Green-veined White




Speckled Wood




Red Admiral




Small Tortoiseshell








Holly Blue




Painted Lady








Silver Y




Small Copper








Six-spot Burnet




Marbled White



The Top 10 species for England, Northern Ireland, Scotland and Wales can be found here.

The big butterfly count will return again next summer to enable us to identify longer term trends in our butterfly species. With your help, we can make the tenth year of this event even bigger and better in 2019.

What you said about big butterfly count 2017

big butterfly count is not just about gathering valuable information about how our common species are faring, it’s also fun and introduces butterflies and butterfly recording to new audiences. Here's what some of the 2017 participants had to say about big butterfly count:

"Well done. Great initiative. Educational, inspiring and important research. Oh - and beautiful." Ms. Procter, Swansea

"We plant lots of nectar rich flowers for the bees, butterflies & bats......We have seen the difference it makes :)" Mr. Steed, Cambridgeshire

"It was a very calming experience to simply sit quietly in the garden and observe nature." Ms. Winn, Midlothian

"My 4 year old daughter helped me and she loved it." Mr. Grayson, South Yorkshire

"I enjoy taking part. I grow plants to get as many butterflies and other wildlife to visit." Mr. Cordner, Co. Down

"It was great fun being a scientist and knowing our information helps." Ms. Meikle, Fife

"Thank you Sir David Attenborough - it was fun sitting in the garden doing nothing for 15 mins!" Ms. Mohandas, London

"Life's too short not to stop and admire butterflies and moths" Ms. Grubb, Cumbria

View Big Butterfly Count website