Common Blue
Polyommatus icarus
Tap image to enlarge · Wikimedia Commons
Overview
The Common Blue is the most abundant blue butterfly on the Sefton Coast and one of the most reliable. Males are a beautiful, vivid blue; females are brown with blue scaling at the wing base. They require Bird's-foot Trefoil as a larval foodplant, which is common on the dune grassland. In July the dune slopes can be alive with them. Males are territorial and will see off rivals and investigate any small blue object.
At a Glance
| Order | Lepidoptera |
| Family | Lycaenidae |
| Habitat | Dune grassland · Coastal grassland · Rough grass with trefoil |
| Diet | Adults: various flowers. Larvae: Bird's-foot Trefoil (primary), other Fabaceae |
| UK population | Widespread but declining in England due to grassland loss |
| Sefton Coast | Common on dune grassland throughout the Sefton Coast; locally abundant in good years |
| Conservation | UK Green List |
Where to See It
Dune grassland wherever Bird's-foot Trefoil grows. Formby and Ainsdale.
Identification
Males: bright violet-blue above with thin black border. Females: brown with orange spots and variable blue sheen. Both have spotted pale grey underside.
Viewing & Photography Tips
Walk any area of dune grassland with Bird's-foot Trefoil in July. Males puddle on damp sand and are very approachable when drinking.
Conservation Status
UK Green List
This species has a favourable conservation status in the UK and remains an important part of Sefton Coast biodiversity.
Frequently Asked Questions
How do I find Common Blue butterflies at Ainsdale?
Look for patches of Bird's-foot Trefoil (a small yellow pea flower) on the dune grassland — wherever the foodplant grows, Common Blues will follow. Males are territorial and often visible on prominent perches. Damp patches of sand attract males puddling for minerals, and they are easy to photograph while drinking.
Related Species
Plan your visit to the Sefton Coast
Marshside RSPB, Formby pinewoods, Ainsdale NNR — practical guides to getting there, what to bring, and the best spots for each season.