The Big Butterfly Count

Nearly 45,000 people took part this year, during a three week period in July and August. Now, the results are in…

Common Blue Butterfly Image: Rabbi WP Thinrod [CC-BY-SA-2.0 (http://creativecommons.org/licenses/by-sa/2.0)], via Wikimedia Commons

The Big Butterfly Count is the largest annual insect survey in the world. Nearly 45,000 people took part this year, during a three week period in July and August. Now, the results are in.

In total, almost 560,000 butterflies were spotted by participants. There were big winners this year, with some species increasing their numbers compared to last year. The Common Blue had increased by 55%, the Red Admiral increased by 43%, the Speckled Wood was up by 28% and, for the first time, the Peacock butterfly was the most abundant butterfly in the survey.

There was also good news for the Small Tortoiseshell which continued its fight back after years of decline. Its population had fallen by 78% since the 1970s and is still scarce in many parts of England. However, this year numbers were higher than they have ever been in a Big Butterfly Count, building on their incredible revival that began last year when they increased 232%, despite this August being the coldest since 1993. The drop in temperature in August did however have an effect on the majority of the UK’s common summer butterflies, curtailing their flight period or hastening them into early hibernation.

The bad news from the survey was the fact that the average number of individual butterflies seen per-count dropped to 15 this year, compared to 23 in 2013. In total, 15 out of 21 of the target species decreased this year in comparison to last year – only 6 species have increased year-on-year.

The common white butterflies all had a disappointing summer. The Large White decreased by 65%, the Small White by 60% and the Green-veined White by 47%. The counts only two migrant species, the Painted Lady and the Silver Y moth also had a disappointing year.

The Big Butterfly Count is run by Butterfly Conservation, supported by Marks and Spencer. Butterfly Conservation Surveys Manager Richard Fox said: “After a good summer in 2013, the big question this year was whether butterflies would continue to recover and build up even greater numbers or slip back again. Thanks to another amazing turnout from the public, we know that the answer is a real mixture. The Small Tortoiseshell had a good year in 2013 and this seems to have acted as a springboard for the species, enabling it to increase massively again this summer. It’s fantastic news for a species that has lost three-quarters of its population since the 1970s. Others such as the Gatekeeper held their ground this year, but sadly, many common butterflies appear to have sunk back from last year’s peak in numbers.”

Overall, this summer was not as good as lepidopterists were hoping for, as many species did not build on the successes of last year. Insect populations are always more unpredictable than bird or mammal populations, and have a natural tendency to have boom and bust years, but Richard Fox does not think this completely explains this year’s results. “The ups and downs driven by weather and parasitic insect cycles are natural variables but then we’ve got human-driven climate change and the massive changes to the landscape that humans have wrought through farming and building,” he said. “This underlines the need to have long-term population studies to see through to the positive and negative human impacts as well.”

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