The number of red admirals in Britain soared over the summer despite the soggy conditions, according to conservationists who said public sightings of the butterflies had risen to their highest since 2010.
Results from the Big Butterfly Count show that sightings of red admirals reached 73,000 over the three-week survey, a rise of 75% on 2016, and as many as were counted in the past three years put together.
The butterflies benefited from the mild winter and warm spring after a good year in 2016, according to Butterfly Conservation, the charity behind the survey. The boom in red admirals saw them come second in the rankings of most commonly seen butterflies in Britain, behind gatekeepers, whose sightings were up 24% on last year to more than 93,000.
Other common butterflies also fared well over the summer, with sightings of commas rising 90% and small coppers up 62% on 2016. Compared to last summer’s count, the number of common blues rose 109%.
The weather during the winter and spring led many species to emerge earlier than usual, meaning some butterfly species peaked before the count started. The wet weather in the summer further reduced the number of butterflies spotted in the survey.
Several species were seen far less than last year, with all three of the UK’s common white butterfly species down. Numbers of green-veined whites were at their lowest since the count began in 2010, with sightings of the other two species at their second-lowest. On average, volunteers spotted only 11 butterflies each during the count, the worst figure recorded by the charity.
“It hasn’t been a vintage summer for butterflies, but there have been some real positives,” Richard Fox, head of recording at Butterfly Conservation, said. “The flurry of red admirals on buddleia bushes, vivid golden commas holding territories along the hedgerows and beautiful flecks of blue and orange among the long grass as common blues and small coppers made the most of the sunshine before the next shower.”
More than three-quarters of the UK’s butterflies have declined in the past 40 years, with some common species, such as the small tortoiseshell, experiencing a dramatic fall in numbers.
While red admirals are now a common sight in British gardens, the butterflies were strictly summer visitors a few decades ago. The butterflies arrived in the spring and summer from the warmer parts of Europe, and bred in the UK before returning south with their offspring for the winter. The butterflies still migrate, but many now overwinter in Britain, making red admirals the most commonly seen butterfly in the winter months.
