Over the last few days I compiled the results of surveys I did of the two butterfly orchid species in Oxfordshire for a status update for the Flora Guardians programme.
I had some site references from the Flora Guardians programme itself and then added in records (primarily from the year 2000 onwards) from the BSBI Distribution database, access to which and the analysis it allows is well worth the BSBI subscription alone. Unfortunately there is a misalignment of boundaries because the administrative county contains all of BSBI's vice county 23 (which I used) but also bits of vice county 22. No matter, I ended up with 26 localities where Greater butterfly orchid has been seen this century, and 5 where Lesser Butterfly orchid has been seen. I also added a site which I have been studying over the last 2 summers, and probably holds the largest number of plants in the county but was on neither database.
I surveyed only 6 of the Greater butterfly orchid localities, though almost certainly these contain the bulk of the plants. I also surveyed 2 of the 5 Lesser butterfly orchids locations. Greenfield Farm (to which there is no public access) had over 500 plants of which 196 produced flowering spikes, an increase of on 2017. The plants are in beech / ash woodland, and thus quite heavily shaded; there is no real herb layer, but there is regrowth of ash and beech and a tangle of brambles. Habitat maintenance is selective; in the 2017/18 winter the bramble was cut back in three quarters of the site but left in the other quarter. Dog's mercury is becoming a problem in one corner, developing a heavy smothering sward, perhaps encouraged by increasing light levels (which we are trying to monitor) because the ash is suffering from die back.
BBOWT's Warburg reserve has both species. An underestimate for certain, I counted around 40 flowering plants of Greater butterfly orchid, scattered quite thinly through the reserve apart from one hotspot. Generally they were in scrub regrowth in areas cleared some years back. Numbers have been stable since 2015, when comparable annual counts started. Lesser butterfly orchid is rare and at Warburg there were only 4 flowering plants growing amongst scrub on the edge of rides. There was also one flowering plant of the hybrid P. x hybrida, last seen (recognised?) in 2003. Some modest scrub clearance around the existing plants might help.
Elsewhere I counted 28 scattered flowering Greater butterfly orchids at Bald Hill, English Nature's Aston Rowant reserve on top of the hill amongst low scrub, and a few plants on the Cornbury estate adjacent to a footpath.
So, a few sizeable colonies of Greater butterfly orchids, a species which is probably under-recorded because there may be more in some of the Chiltern woodlands. By contrast, lesser butterfly orchid is just abut hanging on at Warburg, though there has only ever been a few plants there. Unless the 3 locations that I have yet to look at have plants, it might be that those few remaining at Warburg are the only examples in Oxfordshire.
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| Leaves count! Cornbury |
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| Greater butterfly orchid, Bald Hill |
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| Lesser butterfly orchid with scale, Warburg |
Closer to home I have been out bat detecting having bought a new toy a bat detector which works on my phone, an Echometer touch. It constitutes a microphone which plugs into a smart phone and links to an app. Its clever, providing a chart of a bat echolation sound in what it calls real time expansion or as a heterodyne signal. For lazy people like me who just want to know what bats are out there, it also gives an identification which is correct most of the time, and it gives a gps location. We are in to November, yet even so, possibly because it was a mild evening I picked a noctule and a common pipistrelle near home.
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| Common pipistrelle sound wave |
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