An annual citizen science event run by Phil Harris and Dominica Williamson
Goal: To monitor a butterfly colony and train people how to monitor butterflies
Date: June 22, 2023 Time: 11:00 AM
Location: Loe Bar, Porthleven, Cornwall
On our annual butterfly-monitoring day at Loe Bar, the weather was hot due to a heatwave, with a temperature of 20 degrees Celsius and a light southwesterly wind. The sky was mostly blue with some cumulus clouds. The tide was going out and was at a midway point. Due to the drought, there were brown patches of grass and the paths were very dry. We were hopeful for a successful day of butterfly spotting, especially focusing on the Silver-studded Blue colony that we been monitored since 2007.
The Silver-studded blue Plebejus argus is named after the light blue reflective scales on the underside of most adults, which are visible when light reflects off them. The males of this species are blue, while the females are a less-conspicuous brown. As in past years, new participants were taught how to recognise male and female Silver-studded Blues based on their distinct colouring and flight path behaviour.
Last year, only 16 Silver-studded Blues and one Meadow Brown Maniola jurtina were recorded. However, this year, within the first thirty minutes, 9 Silver-studded Blues were spotted, followed by 21 more in the next thirty minutes. In total, 34 fresh-looking Silver-studded blues were observed, along with 18 Meadow browns, a Common Blue Polyommatus icarus, 2 Large Skippers Ochlodes sylvanus, and 2 Small heaths Coenonympha pamphilus. We were surprised not to find more butterflies, considering the favourable conditions. (It was hard to photograph them this year as they weren’t in cop. Last year we caught more on film.)
The late start to the year, with a cold and long spring, could have contributed to the lower numbers. Additionally, the butterfly habitat had shrunk due to a cliff collapse caused by a storm in 2018, which led to the closure of the entire area. As a result, the colony could not be monitored that year. This year, we walked the old section, as we have done for the past four years, and found that the Silver-studded Blue colony was still present. However, we noticed an increased abundance of Rye grass Lolium perenne, which we hope will not encroach further on the heath-like habitat preferred by the butterflies. We also observed more bracken growth, indicating overgrown paths. During the walk, we recorded Six-spot burnet moths and noticed hundreds of tiny white moths in the colony area.
After the butterfly recording, we enjoyed a cream tea on the cliffs while listening to the surrounding sounds. We were serenaded by Sky Larks (Alauda arvensis) and spotted 10 more of them. At one point, five Choughs were seen dancing, accompanied by their noisy chat, before disappearing from view. Along the new section of path, erected due to the cliff collapse, numerous Stonechats (Saxicola rubicola) could be seen and heard! Finally, at the end of the day, a Buzzard was observed searching for food, while a Cormorant was fishing on the other side. Throughout the day, we also spotted cuckoo spit on honeysuckle, dry rabbit poo (which led to a discussion), grasshoppers, blackbirds, gulls, and 2 Green tiger beetles (Cicindela campestris). We admired the taught dome of the umbrella of the wild carrot (Daucus carota). Phil says the Wild carrot is the best he has seen anywhere – we made a list of plants which we can map against the butterfly record.
Since 2007, Phil Harris and Dominica Williamson have been leading the butterfly recording efforts on the cliffs as you walk south towards the bar at Loe Bar. Each year, they are joined by a group of people who assist in recording the butterflies and their observations. Phil takes the opportunity to teach newcomers about butterfly spotting and the fascinating life cycle of the Silver-studded blue. He particularly focuses on studying the mutualistic symbiotic relationship between the butterfly and two species of black ant, Lasius niger and Lasius alienusits, as well as its food source, common bird’s-foot trefoil.
Throughout the years, the team has been tracking changes in vegetation, the overall landscape, and the butterfly colony itself. The positive news is that the Silver-studded blue colony is surviving. The best records are usually obtained on warm days with warm and dry weather leading up to the recording day. In 2017, they recorded 84 individuals, and in 2010, they recorded an impressive 130 individuals. Phil is optimistic about the potential for the butterfly colony to expand, thanks to the habitat management efforts undertaken by the National Trust in the fields adjacent to the cliff top.
During the recording day, everyone involved did a brilliant job documenting their observations and enjoying the different elements of the day. The recorders on this day were Philip Hills, Ann James, Tamsin Floyd, Andy Hughes and Liz Mitchell.