Notes from a windy isle – 4.7.19

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Let’s Twist Again!

Variety is the spice of life, they say. As I swooshed my butterfly net through golden Bird’s-foot Trefoil and Kidney Vetch, a variety of small and horribly similar-looking little moths fluttered out.

My ability to identify living things correlates positively with their size. By the time you hit micro-moths, I’m floundering tragically in a sea of ignorance. However, today, our quarry had the appealing (and dare I say unusual?) quality of being distinctive.

As the visiting lepidopterists marvelled knowledgably at beige dots in pots, I focused my own search on the most basic suspect profile: that of a tiny, mostly white, flying object.

But there are lots of interesting flying objects on Tiree, and distraction is ever at your elbow.

Take, for example, our Great Yellow Bumblebee or ‘Seillean mòr buidhe’. This species was once present in every county across the UK. Over the last century, its population has declined by 80 per cent. UK Great Yellow Bumblebees are now restricted to flower-rich sites in Caithness, North West Sutherland, Orkney, and the Hebrides. They hang on here at the grace of traditional low-intensity agriculture. But they need urgent assistance to prevent further decline: Britain is thought to have lost a disturbing 97 per cent of its flower-rich grassland since the 1930s.

In the very best habitat, in the very best weather conditions, only one in 10 bees seen might be a Great Yellow. They are extremely rare and, not to be picky, they are in fact a silky caramel colour; unlike the much brighter golden-orange Moss Carder Bee which is regularly mistaken for them.

Fortunately, small measures can be taken locally to provide support. I saw my first queen of 2019 this week. She was inspecting my garden, which is part of a collaborative community project to boost the provision of early nectar sources; link areas of suitable habitat; and monitor Great Yellow numbers. This community project has been led by a resident ecologist – in conjunction with RSPB Scotland and Grow Wild Scotland (who generously provided native wildflower seed).

Or how about Tiree’s butterflies? Members of a recent guided walk group were delighted by long views of a Marsh Fritillary. The wings of these colourful insects resemble stained-glass. Intricate cells of cream, yellow, orange and russet are bordered by thick black lines; just like bright, leaded panes in a banquet hall.

Scottish Marsh Fritillaries are generally darker than their colleagues from elsewhere in the UK. Perhaps this helps our butterflies to absorb the sun’s energy and warm up for action faster; allowing them to make all three days of our Scottish summertime count (mostly for sex, it must be said – but no judgement here).

Marshies are renowned for their ‘go big, or go locally extinct’ life history. As adults, they don’t last long (about two weeks) and they don’t tend to roam far. Virgin females are weighed down by a precious cargo of approximately 350 eggs, which must be deposited on the larval food plant Devil’s-bit Scabeous. They aren’t as coquettish as other lady butterflies; worrying less about Mr Right and being content with Mr Here-Right-Now. Business concluded, eggs laid, and ballast lost, they may take wing (weather permitting) to lay a smaller second or even third clutch; using material from that first and only coupling.

If colonies within a larger regional population become too spread out, and favourable habitat becomes fragmented between colonies, Marsh Fritillaries risk simply fading away. This is down to their short adult life and associated difficulty in dispersing. They are one of Britain’s most threatened butterflies; having been largely lost from the east coast of the UK. Incredibly, this species was rediscovered by children from Tiree Primary School in 2014 after a gap of more than 60 years.

The sun blazed down and there was no shade. After two hours of scouring the hill, my butterfly net was wilting somewhat. The cerulean hue of Common Blue Butterflies was the only thing that looked remotely cool, and heat haze silvered the patchwork of croft fields below.

From behind a rocky rise, an excited shout went up: success. There, in a clear plastic pot, the minute but beautiful Tiree Twist moth sat patiently. It was pearly white all over, with handsome splodges of shimmering bronze on its head and wings. We were the first people to see it in the UK for 12 years – and it is now only found on Tiree.

I’ll let the experts tell you more about this exciting rediscovery in due course; but suffice to say, it was a remarkable find. I’d like to thank our Graziers for kindly allowing access to this site; visiting specialists from, and members of, Butterfly Conservation Scotland for leading the hunt; Tiree’s RSPB Scotland Officer for his assistance with the planning of this attempt; local residents who came along to help search; and the young people visiting from Wilder Ways outdoor school in Fife – who gave up some of their stay on Tiree to take part.

The Tiree Twist is alive and – er – sitting (they didn’t appear keen to do much else), so no doubt we’ll be ‘Twisting Again’ soon!