Welcome to Butterfly Conservation in Somerset and Bristol

RESULTS OF THE BIG BUTTERFLY COUNT

The Small Tortoiseshell suffered its worst summer in the history of the Big Butterfly Count with sightings falling by 32% compared to last year. The population of this once common species has collapsed by 75% since the 1970s. Reasons for the ongoing decline are being investigated with climate change, pollution and parasites all possible culprits.

Populations of Red Admiral and Comma were also well down, by 73% and 40% respectively compared to the high numbers seen in the same period last year, and Gatekeeper fell by 54%.

But many other common species were seen in improved numbers in response to the glorious summer weather, accounting. The three white butterflies each recorded large increases compared to last year, accounting for  more than half of the 964,000 butterflies and moths recorded. The Small White was the most abundant Big Butterfly Count species this summer with numbers up 161% compared to the same period last year. Large White came second up 104% compared to 2017’s count and Green-veined White was up 78% on the same period last year. The whites have had a few lean years so their increased numbers this summer may be due to reduced levels of predation by parasitic wasps or that they benefited from the warm spring and summer.

The Count’s blue butterfly species both enjoyed a good summer. The Holly Blue recorded its highest ever numbers in the history of the project and was up 122% compared to 2017. The Common Blue was up 51% on the same period last year and had its best results since 2010.

An average of just 11 butterflies of the 19 target species were seen per Count this year, a figure only marginally higher than last year - the lowest in the Count’s history. These low numbers are thought to be a result of some species emerging earlier than usual in response to the heatwave which meant numbers were declining before the Count started.

Big Butterfly Count 2018 – top 10 species ranking

  1. Small White                       273,650 seen

  2. Large White                       210,665

  3. Gatekeeper                       72,877

  4. Peacock                            54,287

  5. Meadow Brown                 51,899

  6. Common Blue                   50,118

  7. Green-veined White          49,515

  8. Speckled Wood                35,294

  9. Red Admiral                      33,508

  10. Small Tortoiseshell            23,210

Full results can be found at www.bigbutterflycount.org and the Somerset review of species' fortunes will be in the Spring edition of The Arion.

The Big Butterfly Count is sponsored by B&Q.