Tuesday, 7 June 2016

May 31st 2016- The day of the Butterfly Conservation survey

I've been asked by Butterfly Conservation if I will do a timed survey of the Marsh Fritillaries at Volehouse Moor. It's a species of most concern in Britain and Europe due to its worrying decline over the last few decades, and so monitoring the remaining populations is really important if we are going  to reverse the trend. I'm happy to oblige, and secretly rather proud that they've asked me to be responsible for it.

Jenny at BC sends me through all the forms and the guidelines for the timed count that I'll be undertaking. I'm determined to count the best, most accurate count that any counter has ever counted.

The guidelines are interesting. The survey should be undertaken as near as possible to peak flight period which is about now. If this is achievable, only one count is needed per year.  The methods used for entering data into the database take account of single specimens counted twice (no need for that in my case, I think smugly to myself) I wonder how they work that out. Do they just assume a percentage of dupes? I wonder how many?

It should take place between 10.45am and 15.45pm. I decide that I wouldn't bet on seeing many Marsh Frit after 3pm, so I'm going to do mine at what I reckon is the peak flight hour- between 11am and 12.01pm (I say 12.01 because I can never remember whether 12.00 mid-day counts as am or pm).

Weather should be warm and bright (unusually for a bank holiday in North Devon, it is) with at least 60% sunshine. Wind no more than 5 on the Beaufort scale. Check.

Recordings should be made at a slow, steady pace (My natural pace, in other words), walking in a zigzag pattern across the entire flight area in a fixed time period. This is interesting because it means that I won't walk the top 2 meadows, which have no Marsh Frit. Basically, I will be trying to determine the extent of the flight area, which I know from experience is the 3rd field and the fields either side of it, and then the two fields that lead down to the river. The Marsh Fritillary decrease in frequency as you progress down the slope until by the time you get to the river, there are none flying that I've ever seen. Perhaps today will be the exception, though. I shall look diligently, I promise myself.

With all conditions met, I embark on my quest for the Marsh Frits at 10.45am exactly. I am well chuffed to have started off at exactly the officially approved start time, although the lackadaisical part of me knows that I could actually have started a sloppy 2 minutes earlier and it would have made no difference. This is important scientific work though, so I start precisely and within the guidelines. No Fossey or Goodall could have been more rigorous in their methodology.

I am slightly concerned at the ambiguity of the term 'zig zag' though. Does it mean a classic 45 degree angle or a more determined 22.5 degrees? Without a protractor it's hard to be accurate anyway, so I ask myself the question 'What would Attenborough do' ? I feel the answer from Sir David would probably tell me to get on with it and stop being a buffoon, so I do.

For 70 minutes I comb the fields of Volehouse with my eagle eyes, zigzagging frantically at an angle that I guess to be about 34 degrees (I decided to split the difference), walking at a pace so slow and steady that you  could set a metronome by it, and counting the fritillaries off with a clicker I've bought for the occasion in case I lose track and have to start again. No expense spared, I can tell you.

And the fritillaries seem to know that I'm trying to help their conservation, because they come out in droves. I zigzag across previously unexplored hotspots, and see behaviours that I've never seen. I note males sitting high up on tree leaves, seemingly guarding territory. I see a courtship ritual that I've never noticed before, where the participants circle each other and rub flanks. It seems almost as stylised as that of the Wood White (Leptidea sinapis). I wonder at the number of adults who just sit on grass stalks, not feeding, not apparently guarding territory and not even warming up. What's that all about? Are they just resting?

60 minutes later, I've covered the fields and the butterflies are thinning out. I'm halfway down the last field, and my count is 86 fritillaries. I think that it's all over, since I've never seen one this far down towards the river before, and then, just as reach the end of my session, at 70 minutes, as I turn to leave, I see one final specimen fluttering weakly along. Lucky number 87.  I take a commemorative photograph to mark the occasion, and have a long drink. It's tepid. I'm gutted not to have made the ton, but 87 is a lot more than I expected. It's hot. I'm sunburned. But the fritillaries of Volehouse Moor can consider themselves well and truly counted.

Lucky number 87

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