The Small Blue butterfly: An early indicator of big biodiversity gains at Halnaker Hill Farm

Butterflies are widely recognised as valuable environmental indicators, both for their rapid and sensitive responses to habitat or climatic change, and as representatives for other invertebrate groups which may be more difficult to record – where butterflies occur in diversity and abundance, it is highly likely that other aspects of the fauna and flora are in good shape.

At Halnaker Hill Farm, advisory board member and butterfly enthusiast Neil Hulme is monitoring their progress and will be performing three surveys across the site at different times of the year, to record the full range of different species that fly as summer progresses. The spring survey has now been completed and the results are very exciting.

“I always hoped it would come, as we’ve got very large quantities of its caterpillar’s food-plant, Kidney Vetch, but I didn’t expect it to appear so soon. The arrival of the Small Blue comes with a clear message – the project is delivering huge biodiversity benefits, and quickly,” says Neil, who recorded nearly 50 of the tiny charcoal-coloured butterflies.

Although it’s only the size of a fingernail, the UK’s smallest butterfly is well known for its ability to detect the presence of Kidney Vetch from several kilometres away. Neil adds: “It’s a highly localised and uncommon species, too, listed as Near Threatened in the GB Red List of butterflies, so we’re off to a flying start!”

The good news doesn’t stop there; among the 18 species Neil recorded on the first survey was Dingy Skipper – another of the butterflies prioritised in the advisory board’s Species Action Plan. Although slightly more common and widespread, species such as the Green Hairstreak, Small Copper, Brown Argus, Small Heath and Common Blue have also been keeping Neil busy as he criss-crosses the farm, counting as he goes.

Neil concluded: “I record other wildlife of interest during my visits and I’ve been amazed at the sheer numbers of some insects. I’ve seen vast clouds of the dangly-legged St Mark’s Fly and swarms of the Garden Chafer beetle, with this rich larder providing abundant food for our burgeoning population of farmland birds. Nature is just pouring into Halnaker Hill Farm – it’s so uplifting to see it happening before my eyes.”

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