Tuesday 10 May 2022

Another Sort of Burgundy 8th May 2022

A Spring Sunday and a late start for once, as Mark and myself had arranged to meet in a farm shop cafe at Tring, in the late morning, for a coffee and chat before moving on to Bison Hill on Dunstable Downs to look for Duke of Burgundy butterflies. This would be our first butterfly foray of the year, searching for this now rare and localized, spring flying butterfly, that will be on the wing for just six or so weeks and then will become a memory until next year.

It is not really known why they are called Duke of Burgundy or were once considered to be a fritillary. In the latter case, probably it was the superficially similar patterning on their wings to that of other true fritillaries and the likeness gave rise to them being originally named Mr Vernon's Small Fritillary. Once it was discovered they were not a fritillary at all, but belonged in an entirely separate genus, the name was dropped but no one can point to why Duke or Burgundy were then thought appropriate for them, the two names being initially used separately before being combined into the name they now carry to this day. 

It was already unseasonably warm by the time we parked in a tiny layby at the side of the road ascending Bison Hill, a road beloved of serious cyclists, testing their limits of endurance as they pedal up the severe incline . Bison Hill forms part of the gently undulating Dunstable Downs and is so named because it is near Whipsnade Zoo and you can look down from the hill onto the zoo's bison enclosure over two hundred metres below. 

Bison Hill is ideal for the Duke of Burgundy, facing, as it does, northwest and consisting of short, chalk downland grass with lusher areas no longer heavily grazed, that allow cowslips, the butterfly's foodplant, to prosper. It is an ongoing task to manage this habitat and keep it  suitable, just as it is in other areas where this special and threatened butterfly is still present.

There were quite a number of people, walking the top of the downs, out to enjoy the warm sunshine but we had our mind on other matters and  followed a less frequented  track of hard, sun baked earth, winding its way across a lower part of Bison Hill.

The breeze carried the pungent, sickly aroma of emerging may blossom, a froth of white on leaves still shiny and new, like green gloss paint yet to dull with age. Profusions of cowslips formed  pale yellow shadows of colour across the varying shades of brightening green that covered the slopes. It really was an uplifting experience to be out on a day such as this.

A bank of Cowslips.Home for the Duke of Burgundy

But where were the dukes? If you are in the right area they should not be too hard to find as the males are highly territorial, defending a small select area, intercepting passing insects and in the process making themselves conspicuous. The problem is that they are now not nearly so abundant as in previous times and can only be found in small, widely scattered colonies. Hotspots if you like that require some searching for. Today we found just half a dozen in this area and all were males.

Cowslips being their larval foodplant, it seemed logical to concentrate our searching in areas where they were plentiful  but  we found our first Duke capriciously holding territory on a narrow track of bare earth, no more than a sheep track, winding an uncertain course through the grass.

I am taken aback every year at how small they are. A tiny, pugnacious and fast moving, superficially dark brown butterfly that can be hard to follow as it flies. When settled it sits on a blade of grass or bramble leaf, opening its wings to the  sun, embracing the warmth but is never still for long. Always there will be an insect or another of its kind that comes to upset it and away it goes in fast flying, helter skelter pursuit of the interloper to its territory.

You can seize the moment and crawl or walk right up to a Duke when it is still and get no discernible reaction, but make it quick, for it is forever frustrating as any passing insect causes it to fly up in investigation and one then has to search for it all over again, safe however in the knowledge it is always faithful to its small territory and will usually have settled somewhere not too distant. On occasions, if you are lucky it will even return to whence it departed

Once settled it can be seen how agreeably marked they are. A tiny dark jewell of an insect, a miracle of nature that unfailingly imparts a sense of innocent discovery and fulfilment when it is found and admired.

The open upperwings are chequered orange and brown whilst the hind underwings are beautifully patterned, similar to a fritillary, with two conspicuous bands of  irregular shaped, silver white panels.

Of course there were other butterflies on the wing and chief amongst these were Green Hairstreaks, flying hesitantly when disturbed and soon to drop into the short grass, where they wander along and examine thin grass stems with great deliberation, turning and twisting so that their emerald green underwings shimmer like burnished metal in the sun.

Green Hairstreak
Brown Argus, Grizzled and Dingy Skippers are another matter, all being much more active, their wings natural solar panels that energise them into their fast flight across the sward, testing one's patience and endurance on the steep slopes they patrol.

Brown Argus

Grizzled Skipper

Dingy Skipper

After an enjoyable three hours I was beginning to flag. A bank of cowslips adjacent to the car provided a suitable valedictory as we watched a spectacular, skyward spiralling tussle between a Duke and a Dingy Skipper. 

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