How has this year’s unpredictable weather affected butterfly populations in the county?
What better way to start the weekend than a stroll across a Suffolk heath in search of butterflies?
We had congregated at Sutton Heath near Sutton Hoo to look for graylings and small coppers under the direction of Kevin Ling and Jillian Macready, members of the Suffolk branch of the Butterfly Conservation charity.
The organisation holds regular walks, working parties and moth trap events at locations across the county and throughout the year, designed to create habitats, survey population numbers and educate.
Bewitched
The initial overcast and breezy conditions weren’t ideal for butterflies but within minutes we had seen our first grayling which favours the sandy coastal heath habitat found at Sutton Heath where purple heather, fern and gorse are in abundance. Graylings, I discovered, are best spotted in flight - as they jolt and tack just above the vegetation and offer orange flashes of their wing markings. But once they are on the ground, where they like to spend time, they are masters of camouflage - with their wings closed tightly to show only the mottled grey underwing, which blends in perfectly with the heath floor and woody stems of the heather.
The grayling demonstrates why people become bewitched by butterflies - many are adapted to survive in a certain kind of habitat and they and their caterpillars may only feed on a select number of plants. It means many species have their own unique character and habits.
As if to underline this rigid preference for a certain habitat we entered a small wooded area and only a few steps in were greeted by a speckled wood butterfly, dancing at waist height in front of us - its brown and white markings on show. Later, as we emerged from the trees and the sun came out, we gathered round a small copper butterfly content for its orange and black wing patterns to be admired at length as it feasted on nectar from a flower on a gorse bush.
Emerging early
Walking with Kevin and Jillian made the whole experience much more fulfilling as they were able to talk with knowledge about these habits. Kevin also spoke about how the unusual weather we have experienced this year has impacted on different species.
He said the mild weather in February and March encouraged some hibernating species to emerge early but immediately after there was a protracted cold spell, the notorious Beast from the East, which killed off many of these before they had a chance to mate. This meant fewer eggs were laid than normal.
Kevin said: “By the time the eggs hatched, it was getting really hot - this is perfect for adult butterflies, as they nectar, mate and lay eggs. However this had a profound effect for caterpillars, as the burning heat dries out the larval host plants, many of which withered severely, meaning the caterpillars couldn’t feed up, and many perished before pupation.”
One butterfly that missed its spring breeding opportunity was the small tortoiseshell. A once common site in our countryside and gardens, this species has been all but absent from our nettle patches this summer, according to Kevin, who said comma and peacock butterflies have also been impacted.
Woodland winners
There were some clear winners this year though - butterfly species found in woodland - purple and white-letter hairstreaks, white admiral, silver-washed fritillary and purple emperor - were able to take shade from the heat and all appear to have done reasonably well and from records received so far seem to be widely distributed.
In respect of the two hairstreak species mentioned there have been more records from gardens than in previous years and a count of several hundred purple hairstreak was reported on Rushmere Heath Golf Course in July. There has also been an influx of whites on the wing this summer, with large white leading the way in numbers seen. They managed this by quickly breeding through two life cycles, and then receiving reinforcements from a summer immigration.
But Kevin said among butterfly species that produce second generations there have been a large number of individuals which are smaller in size than normal. This has been particularly evident with common blue, small copper, small heath, holly blue, speckled wood and green-veined white.
Kevin added: “This is the consequence of poor development and growth in the caterpillar due to parched food plants and the impact of hot temperatures on pupation.”
A key Suffolk site which has been extensively managed by Suffolk Butterfly Conservation in recent years is Purdis Heath in Ipswich. Silver-studded blue had their best year for very many at this site while around 2,000 were counted at a site in Dunwich where they are also found.
Big Butterfly Count
July and August saw Butterfly Conservation’s ‘Big Butterfly Count’ - a key public recording of butterflies, which helps assess the health of our environment. As this survey relies heavily on garden and public space sightings and counting the familiar species, the damage done to the early flyers, such as comma, small tortoiseshell and peacock, will no doubt see a reduction in the numbers seen, according to Kevin.
Parched food plants, the cold spring and weak first broods will all have significant impact on next year’s butterfly counts; only then will we be able to count the damage done to butterfly populations in 2018.
Kevin added: “For many, what seemed like a glorious summer at the time, has failed to bring the normal variety of species to our gardens but August has provided some much needed rain and some wildflowers are looking a little more refreshed.
“After the last severe drought that the region experienced, in 1976, the wider countryside species took several years to recover, while for specialist butterflies such as the silver-studded blue, a full recovery has never been possible.
“This is a testing time for our butterflies and we need the help of everyone to ensure that we can enjoy them for years to come.”
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