Second brood Small Blue on the South Oxon Downs – 12th Aug

Yesterday afternoon I made the effort to visit a favourite Oxon site for one of my favourite butterflies. Small Blue, following their peak emergence in mid-May, produce a usually more limited second brood from late July through August. Pressure on the available sunny days in May (see here) meant I didn ‘t make it up to Lowbury Hill, the highest point on the downs above Blewbury. I last found Small Blue here in June 2012, so it was good to get sightings again upon fitting this little excursion into the Rn’S British butterfly summer.

Seeing them is usually weather dependent, and as the walk out and back from Westway above Blewbury is around five miles any attempt is best undertaken on a sunny day. But I always enjoy wandering on this part of the Downs whatever is or isn’t seen. Yesterday conditions improved through the afternoon, so by the time I arrived on site things were pretty much perfect for flying butterflies. I counted 8 – 9 Small Blue in all along a hedgerow just to the north of Lowbury Hill (SU540826) that is a hot spot. They are never easy to capture being so tiny but these pictures (below) compare with my best from previous years.

Small Blue

Small Blue

small blue_01.1505 lowbury hill

Amongst the other species flying here I was again struck by the size difference between individual female Common Blue and Brown Argus. Hence any potential Small Blue I picked out needed to be checked very carefully since some of those other butterflies were barely larger. To complicate things further the wingspan of Small Blue themselves can vary from 16 to 25mm. The food plants are Horseshoe and Kidney Vetch, and Common Bird’s-foot Trefoil. Typical colonies in isolated and sheltered locations number a few dozen adults though much larger concentrations do occur. And that’s the miniature jewels that are Britain’s smallest butterfly covered properly for the season.

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