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British farmland butterflies bounce back after 2013 summer, survey finds

 
Common Blue Butterfly

A common blue butterfly. Photograph: Laura Sivell/Papilio/Corbis

 

Powered by Guardian.co.ukThis article titled “British farmland butterflies bounce back after 2013 summer, survey finds” was written by Jessica Aldred, for The Guardian on Wednesday 19th February 2014 06.00 UTC

The warm and sunny summer of 2013 enabled British farmland butterflies to bounce back from a crash in numbers in 2012, a new survey has found.

Results of the Wider Countryside Butterfly Survey (WCBS) show that the majority of farmland species have recovered after the worst year on record for butterflies in 2012, when 52 out of 56 British species monitored suffered declines as a result of miserably wet weather. Individual species that recorded an increase in 2013 included the brimstone, common blue, small and large skipper and small tortoiseshell.

The annual survey, conducted by a coalition of conservation agencies aiming to assess the health of butterfly populations across the wider countryside, counted butterflies in more than 850 areas of 1sqkm in England, Wales, Scotland and Northern Ireland during July and August.

Recorders saw an average of 85 butterflies of five species per survey during the two-month period – almost double the numbers recorded in 2012.

After a harsh winter and delayed spring, the summer of 2013 was among the 10 warmest summers since records began, with 588 hours of sunshine making it the seventh sunniest summer. A prolonged heatwave in the middle of July saw temperatures regularly passing 30C. In contrast, 2012 was the UK’s second wettest year on record, with downpours and flooding.

Wet and windy weather disrupts breeding, with butterflies sometimes dying before they can reproduce, greater incidents of egg mortality and susceptibility to pathogens, especially fungi. Hot summers – provided there is no drought that kills food sources – are ideal for the insects to breed. “Butterflies are cold-blooded so a hot summer heats them up well and gives them lots of energy to fly around, and creates lots of good nectar sources for feeding,” explained WCBS co-ordinator, Dr Zoë Randle.

Small Tortoiseshell Butterfly

A small tortoiseshell butterfly. Photograph: Sarah Niemann

“Farmland butterflies really thrived last year primarily due to the fantastic summer weather which provided ideal conditions with several recording their best ever WCBS results.”

The small tortoiseshell, which has suffered an ongoing decline, recorded its best summer since the start of the survey, which began in 2009. More than 6,833 individuals were counted, with the butterfly seen in 80% of squares compared to just 40% in 2012.

In 2012, numbers of the common blue plummeted by 60%, but the species enjoyed a good year in 2013 with an average five-fold increase in abundance per square surveyed. The small copper and brimstone also thrived, and were both more widespread and abundant than in the previous year.

The large white and small white butterflies, commonly known as “cabbage whites”, were also recorded in large numbers, with more than twice the number of large whites counted per square and five times the number of small whites in 2013 than in 2012.

Meadow Brown Butterfly

A meadow brown butterfly. Photograph: Richard Garvey-Williams/Alamy

 

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