325 butterflies and counting!

Silver-studded Blue butterfly at Hazeley Heath by Dave Braddock.

The RSPB has done a lot work on Hazeley Heath over the last couple of years to improve and increase the area of suitable habitat for Silver-studded Blue butterflies. Before 2016 they only had about 3.45ha of suitable habitat with an annual count of around 20 butterflies. After winter 2016, this had been increased to 6.1ha with an annual count of 50+ butterflies. This area was maintained in 2017 and the butterflies increased to around 192! In 2018, further habitat creation has provided 10.12ha of suitable habitat and this summer they’ve had peak counts of 325 butterflies on the wing!

In Britain the Silver-studded Blue butterfly is almost exclusively tied to lowland heathland. It’s nationally scarce and extinct over much of its former range because of habitat loss. The Silver-studded Blue requires warm soil conditions and therefore needs short vegetation – preferring young heather on south-facing slopes. The food plants for the caterpillars include Heather (ling), Bell Heather, Cross-leaved Heath and Gorse. Bell Heather and Cross-leaved Heath also provide a nectar source for the adults as they flower earlier than ling. It has a close association with two common heathland ant species – the caterpillars pupate within an ant’s nest and will even attend the newly emerged adult butterflies until they fly. The ants require warm, open areas and the female butterfly will only lay her eggs where she can detect ant pheromones.

Management to improve heathland habitats for Silver-studded Blues involves creating a mosaic containing bare patches, young heather plants and improving existing areas of Bell Heather and Cross-leaved Heath by mowing, scraping and hand pulling. Essential work for this sedentary species that often flies less than 20m a day!

Warden Jo (with pictures by RSPB’s Dave Braddock)

Silver-studded Blue butterfly at Hazeley Heath by Dave Braddock.