It’s not all about trees and eagles, you know! One of the many tasks that we carry out here at Beinn Eighe NNR during the summer months is butterfly surveys. Butterflies are an extremely useful indicator of the overall health of an ecosystem, and may also provide early warnings of climate change, as species normally associated with warmer climates to the south are gradually being recorded further north each year.
At Beinn Eighe we carry out butterfly surveys on a weekly basis along a fixed 1.2 km route or transect from the beginning of April to the end of September, on days when weather conditions are suitable for butterfly activity. Having a fixed route provides a control method which allows butterfly sightings to be compared at the same site every year, as weather conditions will vary.
When carrying out the survey, our surveyors walk the transect, recording any butterflies that they see within a 5 metre width along the route. We also record any moths, dragonflies and damselflies which are also good indicators of ecosystem health. As well as species and numbers, we also record information such as weather conditions, wind speed/direction and cloud cover. Once completed, the survey data is entered online at the UK Butterfly Monitoring Scheme website, where it becomes part of the national record along with data from thousands of similar weekly butterfly surveys being carried out across the UK.
One of the butterfly species we’ve recorded on our surveys over the last few weeks is the speckled wood. This pale brown butterfly with white markings can be seen throughout the summer, preferring the dappled light of woodland habitats and feeding on common grasses such as cock’s foot and Yorkshire fog. Another recent record at the reserve is the large white butterfly which, although widespread across most of the UK throughout the summer, is much less common in north-west Scotland.
By far the most frequently recorded butterfly during the month of August has been the Scotch argus, which is easily identifiable from its dark brown wings, orange bands and distinctive eyespots. Found mainly in the Highlands and south west of Scotland, it appears for only a few short weeks between late July and early September. Despite its name, the Scotch argus is not entirely indigenous to Scotland, as two isolated populations also occur in northern England, though its population there appears to be in decline. Favouring damp grasslands, bogs and woodland clearings up to an altitude of 500 metres, there is no shortage of suitable habitat for the Scotch argus butterfly here at Beinn Eighe. The Scotch argus has an ability to survive cooler temperatures than other butterflies, making it likely to have been among the first butterfly species to recolonize the British Isles following the last Ice age.
Beinn Eighe’s ancient woodlands, wet heath and bog habitats aren’t just favoured by butterflies, they are also ideal habitat for dragonflies and damselflies. Recent records at the reserve for these amazing insects include large red damselflies, common hawkers, azure hawkers, golden-ringed dragonflies and many Highland darters.
One dragonfly species we frequently record at here Beinn Eighe is the golden-ringed dragonfly. Easy to identify with its black body, distinctive golden-yellow bands and striking green eyes, the female golden-ringed dragonfly is the longest dragonfly in the British Isles, due to her long ovipositor (the tubular organ through which a female deposits her eggs). You may see these beautiful dragonflies patrolling back and forth above lochans, mountain streams and other small bodies of water at the reserve, looking for small flying insects which they prey upon.
Now, moving towards the end of September, the butterfly survey season will soon be drawing to a close and the completed data for this year will provide yet another page in the ongoing story of Britain’s butterfly (and dragonfly) population.
With many species, not just butterflies, facing an uncertain future due to threats such as habitat loss and climate change, the data from our butterfly surveys will help to ensure that conservation efforts are targeted where they are needed most, as well as help to assess the effectiveness of current conservation strategies.
And a final word on the transects: these have to be carried out under specific conditions. Look at the UK Butterfly Monitoring Scheme methodology page for information on this. Not only that, but these conditions vary with latitude – in northern areas we can get away with 11°C as long as there is enough sun. It’s far from just randomly wandering around waving a butterfly net !
Next month? More voluntary work, and a look at some of the other wildlife we have on the Beinn Eighe National Nature Reserve
For more information, look at our website. The Beinn Eighe Reserve Visitor Centre is open from April until the end of October and has an award-winning display about the reserve, along with a range of walking trails from ten minutes to as much as a full day.
The view from the Mountain Trail – a four hour circular walk in stunning scenery.
Butterfly and dragonfly text courtesy of Stuart Mackenzie, SRUC Placement.
All images ©Lorne Gill/SNH.