Butterfly monitoring at Trelissick

Illustration of a painted lady butterfly by Sonia Hensler

In a delightfully unseasonal update, we have decided to turn our backs on the howling wind and seemingly incessant rains of November. Instead we will cast our minds back to those halcyon days of summer past and look at how our butterflies were doing at Tregew, on the Trelissick Estate. Some of these butterflies remain out and about well into autumn – especially with temperatures as mild as they have been this year – so we have in fact only just bid them farewell…

Over the summer, our ranger ranks were bolstered by the welcome addition of Izzi, who came to us on a four-month contract having previously worked with Dorset Council at Durlston National Park and brought along her enthusiasm and knowledge of butterflies. Harnessing this interest, we asked her to undertake a survey of our wildlife fields at Tregew to record our butterfly population. Although a more numbers-based report was produced for our own ‘in-house’ purposes, what follows is a friendlier and more accessible version of her findings.

This summer has been a good year for butterflies at Tregew with Izzi’s records numbering in the hundreds throughout July. This is an encouraging sign, especially considering the harrowing reports highlighting widespread decline in insect numbers across the country and may suggest that our current habitat management is supporting butterflies well.

Meadow brown
A meadow brown butterfly on some heather at Trelissick, Cornwall
Meadow brown

Meadow Browns were by far the most numerous species we found, accounting for over half of the total amount of butterflies recorded. Hot on their heels was the closely related and similarly coloured Gatekeeper which can be distinguished from a Meadow Brown because it is smaller, has a generally more orange colour and a row of white dots on the underwing. These butterflies are not only common, but also undaunted about flying on dreary days when most other species would think twice (another contributing factor to high records).

Common Blue butterfly
Common Blue butterfly on yellow flower at Trelissick, Cornwall
Common Blue butterfly

Seemingly mirroring the warm sunshine and clear skies, the ‘Blue’ family were about in good numbers during early summer. The most frequently recorded was the aptly named Common Blue, often found fluttering near its favoured food-plant of Bird’s Foot Trefoil, which can be found in abundance throughout our community orchard and the wildflower meadow above.

Staying close to the hedgerows and favouring the shade of the woodland, the comparatively pale Holly Blue was also spotted regularly whilst further afield, Cornwall received reports of the Long-Tailed Blue migrating to our shores from Europe. A glimpse of the future perhaps where warmer summers might mean we see more typically Southern species migrate to our shores.

Silver-washed fritillary
Illustration of a silver washed fritillary butterfly by Sonia Hensler
Silver-washed fritillary

Next door to our fields at Tregew is Roundwood, home to an impressive Iron-Age fort and apparently several Silver-washed Fritillary. During late July and into August we had a number of fleeting encounters with this magnificent butterfly. Strikingly orange and black, this is Britain’s largest member of the Fritillary family, recognisable by its characteristically swooping flight pattern on pointed wings with their silver ‘wash’ on the underside. This species declined considerably during the twentieth century, but it seems their numbers are on the rise once more….and that includes Trelissick!

Painted lady
Painted lady butterfly at Tregew on the Trelissick estate, Cornwall
Painted lady

Another famous migrant, the Painted Lady, was seen in relatively good numbers this year. These well-known butterflies undertake one of the most ambitious and spectacular migrations in the insect world, flying all the way from North Africa, the Middle-East and Asia in their millions to colonise Europe for the summer, sometimes arriving in huge numbers. It is certainly a wonder that an insect weighing barely a gram and with a brain as tiny as a pin prick can navigate such a vast distance, battling winds and crossing oceans in its quest for suitable habitat. They can cover as many as 100 miles in a day and reach speeds of nearly 30 miles per hour! Perhaps because of these considerable exertions, the Painted Lady is the world’s most widely distributed butterfly and is found on every continent bar Australia and Antarctica!

Red admiral
Red admiral butterfly on bramble flowers at Trelissick, Cornwall
Red admiral

A close relation, the large and famous Red Admiral, was also seen and recorded consistently throughout the summer and into early autumn. Red Admirals love Buddleia and can often be found fluttering in groups around its large, purple flower heads. Down on the South Woodland Walk, there is a sap-run on one of our large Turkey Oaks caused by a fungus called Ganniderma. Red Admirals, Hornets and Wasps have congregated there all summer long to sample the sweet delights of freshly oozing sap. During the last weeks of September, many were also recorded gathering at clusters of ivy flowers to stock up on nectar for the long winter hibernation ahead.

Look out for the male speckled wood basking in a patch of sunlight
A speckled wood butterfly pauses on a fern with wings spread
Look out for the male speckled wood basking in a patch of sunlight

As the summer came to an end, the changing season coaxed out the aptly named Speckled Wood; loving as it does, the dappled shade of trees and hedgerows. I typically associate seeing the Speckled Wood with the ripening of the first blackberries and this species continue to be on the wing well into autumn. The Speckled Wood feeds on honeydew in the tree tops and are seldom seen feeding on flowers.

Another butterfly that can sometimes be seen this late, even into November, is the stunning Clouded Yellow which has been recorded at Trelissick and along the South West coast this year. These attractive members of the white family are another migrant and head for Britain from Africa and Southern Europe. They favour Clover and other leguminous plants. Sometimes confused with Brimstones, Clouded Yellows are smaller in size and typically have a richer, golden-yellow colouring. Clouded Yellows are seen most years but – like the Painted Lady, they will infrequently migrate en masse in what is affectionately termed a ‘Clouded Yellow Year’. One such famous year, in 1947, an estimated 36,000 of these butterflies appeared on our shores!

The beautiful blue, almost ghost-like flowers of the hairy vetch. A member of the pea family, this character likes to climb up other plants which it takes into custody with grasping little tendrils.
Hairy vetch growing at Trelissick, Cornwall
The beautiful blue, almost ghost-like flowers of the hairy vetch. A member of the pea family, this character likes to climb up other plants which it takes into custody with grasping little tendrils.

The habitat management at Tregew, such as refraining from using any herbicides and frequent cutting, although not implemented specifically to encourage butterflies, has created habitats where many wildflower species can establish to benefit a vast array of pollinators and other insects. In the woodland at Roundwood, we have thinned out many non-native and shade-casting trees to increase light levels, and stimulate the growth of woodland wildflowers and heather. It is very encouraging to collect such positive records of high insect numbers and gives us the motivation to carry on and keep helping the area to revert from farmland into a haven for our native, Cornish wildlife.

- The National Trust Ranger team, Trelissick and North Helford