Forvie is a tough place to be a butterfly. On most days, the temperature here is several degrees lower than even a few miles inland; not great for warmth-loving insects. We’re often beset by the dreaded haar, that infamous dense fog that rolls in off the North Sea, coating everything in water droplets and sending the temperature plummeting. The rest of the time it’s almost relentlessly windy – even in high summer. Moreover, the winters here can be long and cold, making overwinter survival a serious challenge.
Add to that the stunted nature of the vegetation, growing as it does in harsh ground conditions, which consequently makes finding food and shelter difficult. Sounds like a tough gig, right enough. Who’d be a butterfly in this environment?
Well, for all that, there are a number of species that do eke out a living here, many of which are on the wing right now. They have variously different strategies for coping with the conditions, allowing them to survive and thrive in this challenging environment. Here are some of the key players.
1. The Vanessids
The Vanessids comprise four attractive and brightly-coloured species: Small Tortoiseshell, Peacock, Red Admiral and Painted Lady. The name ‘vanessid’ comes from the Latin names of the latter two species (Vanessa atalanta and Vanessa cardui respectively). These species are all strong fliers, and can travel unexpectedly vast distances. The Painted Lady is the most celebrated in this respect, undertaking an amazing migration from North Africa through Europe to the UK each summer.
While the warmth-loving Painted Lady cannot survive the Scottish winter at any part of its life-cycle, the Small Tortoiseshell can and does overwinter with us. They can often be found in cool, dark places like garden sheds or garages, where they enter a state of torpor – suspended animation, if you like – before resuming their lives again the following spring. Late summer is a great time to see the Vanessids at their best – check out any tall flowering plants like thistles, Ragwort or Valerian.
2. The grassland specialists
Although the wildflower season at Forvie is short, both in terms of time and the stature of the flowers themselves, we do rather better for grasses. It’s thought that as our climate warms and becomes wetter, Forvie Moor may become more grassy, rather than heathery and, er, crowberry-y. And there are some species of butterflies that are well-placed to take advantage of this.
The Ringlet is a relatively recent addition to the Forvie butterfly fauna. They were absent, or at least very scarce, when I arrived at the Reserve in 2007. Nowadays, however, they can be quite abundant in the grassier areas of the Reserve, such as around the Forvie Centre and along the estuary side of the Dune Trail – look out for a dark-chocolate-coloured butterfly flitting weakly among the grass stems. While many butterfly species in the UK are declining, it’s heartening to see others, like our Ringlets, taking advantage of environmental change.
The Small Heath is another denizen of grassland, whose caterpillars feed on fine grasses like Fescues, which are plentiful at Forvie. As a result, Small Heaths are plentiful as well. If a tiny, light-orange-and-silver-grey butterfly flits past your bootlaces on the Reserve just now, it’s likely to be one of these.
3. Wildflower specialists
For other species of butterfly, grasses are no use at all – wildflowers are where it’s at, for both caterpillars and adults. The most obvious exponent of this strategy is the Dark Green Fritillary. Its name is somewhat confusing, since it is very obviously orange rather than green. But there are several fritillary species that all look very similar, and in this one, its distinguishing feature is the green underside of the hindwings.
Dark Green Fritillary caterpillars depend on Violets as a food source, while the adults enjoy nectar-rich flowers like Knapweed, Marsh Thistle and Wild Thyme. True wildflower connoisseurs, I would say.
Much more sensibly named is the Common Blue. It’s common, and blue. But even then, there’s a twist as the females are brown-with-blue-bits rather than all blue like the male pictured below. These tiny, highly active butterflies nectar on all sorts of flowers, while their caterpillars feed on Bird’s foot Trefoil – remember our recent wildflower blog?!
A real specialist is the Grayling. This unobtrusive yet attractive butterfly likes a mix of short grass, nectar-rich flowers and bare, sandy ground upon which it can bask and catch some rays of sunshine. It’s perfectly adapted to this niche, and when it lands on the ground, it practically disappears – its underwings are brilliant camouflage against the sand.
Sadly, Graylings have become noticeably scarcer at Forvie in recent years, perhaps due to the effects of climate change, or maybe due to the decline in the local Rabbit population (Rabbits create the mosaic of bare ground and short vegetation beloved of Graylings). But they seem to have had a bit of a resurgence in just the last couple of summers – here’s hoping they continue to grace the Reserve in the face of continuing environmental change.
Here at Forvie, staff and volunteers undertake a weekly butterfly survey from spring through to autumn. This involves walking a fixed route through the Reserve, known as a transect, and recording the butterflies seen en-route. This has been taking place since the late 1970s – one of the longest-running surveys of its kind in the UK – and feeds data into a national archive via Butterfly Conservation’s Butterfly Monitoring Scheme. Most of what’s known about our butterflies’ distribution and abundance (or otherwise) comes from this sort of work.
It’s not all about countryside professionals though. You, dear reader (I’ve always wanted to say that), can also make a contribution. Butterfly Conservation also organise a citizen-science project, the Big Butterfly Count, each summer, and anyone can take part. This coming weekend marks the end of the 2020 Big Butterfly Count, and we’ll await the results in due course. Perhaps something to consider for next summer then?
Meantime, enjoy the rest of the 2020 butterfly season, while it lasts, and stay safe!