Butterfly Survey GroupCounting the butterflies of Swanage, summer after summer
Butterflies are one of the best signs of how healthy a place is for wildlife. When they do well, the plants and insects around them are usually doing well too.
A small group of volunteers walks set routes on Swanage's green spaces through the summer, counting every butterfly they see. In 2026 we recorded 18 species, the most since our records here began in 2023. We'd love you to join us, and we can provide training if need be.
Four summers of counts
We walk roughly the same number of surveys each year, so the totals give a fair picture of how each summer went. Butterfly numbers rise and fall a lot with the weather, so it's the pattern over several years that matters most.
| Year | Walks | Butterflies counted | Species |
|---|---|---|---|
| 2023 | 23 | 16 | |
| 2024 | 26 | 15 | |
| 2025 | 23 | 16 | |
| 2026 | 23 | 18 |
2023 was a bumper year. Numbers dropped sharply in 2024 and have since recovered to around 700 a year, while the number of species has crept up.
The year of the clouded yellow
The stand-out of 2026 was the clouded yellow. In earlier years we saw just one or two. This summer we counted 23, and recorders across Dorset saw the same rise.
Clouded yellows are migrants. Most fly north from southern Europe each year, and their numbers here depend on how many make the journey. Hot summer winds from the continent may have carried more of them across the Channel this year.
Butterflies we've seen
These are the 18 species our volunteers have identified on their walks.
Large white
Pieris brassicae
Small white
Pieris rapae
Brimstone
Gonepteryx rhamni
Meadow brown
Maniola jurtina
Marbled white
Melanargia galathea
Red admiral
Vanessa atalanta
Peacock
Aglais io
Painted lady
Vanessa carduiClouded yellow
Colias croceus2026 highlight
Common blue
Polyommatus icarus
Holly blue
Celastrina argiolus
Small skipper
Thymelicus sylvestris
Large skipper
Ochlodes sylvanus
Essex skipper
Thymelicus lineola
Wall
Lasiommata megera
Gatekeeper
Pyronia tithonus
Ringlet
Aphantopus hyperantus
Speckled wood
Pararge aegeria
How a survey walk works
We use a method called a transect. That simply means walking the same route, in the same way, on each visit, so one year can be fairly compared with the next.
- Pick a fine day. Butterflies fly when it's warm, sunny and not too windy, so we walk in good weather.
- Walk the route slowly. Each route is split into sections, and we walk them at a steady pace.
- Count what you see. We note each butterfly and its species. Experienced volunteers help with tricky ones, like telling the skippers apart.
- Share the results. Counts are added up at the end of the season and shared with Swanage Town Council.
Join us
We're a group of eight trained volunteers, and there's room for more. You don't need to know your butterflies. We provide training if you need it, and you'll learn quickly walking alongside others.
You don't have to come on every walk. If you enjoy being outside on a sunny day and like the idea of helping local wildlife, there's a place for you.
Want to join us next summer? Email hello@sustainableswanage.uk and we'll be in touch about training and the first walks.
Survey figures come from the Butterfly Survey Group's records for 2023 to 2026. For more about butterflies across the county, visit Dorset Butterflies.
Photo credits
Species photos are from Wikimedia Commons and are used under Creative Commons licences. Large white: gailhampshire, CC BY 2.0; Small white: Charles J. Sharp, CC BY-SA 4.0; Brimstone: Charles J. Sharp, CC BY-SA 4.0; Meadow brown: Charles J. Sharp, CC BY-SA 4.0; Marbled white: Charles J. Sharp, CC BY-SA 4.0; Red admiral: Christian Fischer, CC BY-SA 4.0; Peacock: Charles J. Sharp, CC BY-SA 3.0; Painted lady: Jean-Pol Grandmont, CC BY 3.0; Clouded yellow: Hectonichus, CC BY-SA 4.0; Common blue: Charles J. Sharp, CC BY-SA 4.0; Holly blue: Charles J. Sharp, CC BY-SA 4.0; Small skipper: Ivar Leidus, CC BY-SA 4.0; Large skipper: Andreas Eichler, CC BY-SA 4.0; Essex skipper: Charles J. Sharp, CC BY-SA 3.0; Wall: Charles J. Sharp, CC BY-SA 4.0; Gatekeeper: Charles J. Sharp, CC BY-SA 4.0; Ringlet: Ivar Leidus, CC BY-SA 4.0; Speckled wood: Charles J. Sharp, CC BY-SA 4.0.