BUTTERFLY CONSERVATION UPPER THAMES BRANCH
Purple Emperor (A. iris) Report for 2008
Dennis Dell
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Purple Emperor m. Photo © David Dennis |
Acknowledgements
I'm very grateful to all of you [not all UTB members] who submitted reports: see Appendix for details of participants. I would also like to express my appreciation to those who told me about people who had informed them of sightings, in other words, second hand reports. In this way, over these last 5 years, we have built up a large network of observers. I apologise if I've left anyone out.
1. Introduction
As in previous reports, the observations in detail may be found in the Appendix (see end of report). Also, as mentioned in previous years, it is almost impossible to be able to register the number of individuals seen. Therefore, I have used, mainly, the concept of 'sightings' together with periods of activity, or 'flight events'. In addition, I have not included, in the Appendix, the additional visits people made to woods when they made no sightings.
2. Summary
- About 82 sightings were made [last year it was 55]. Sightings were made at 22 localities. Last year, the figure was 17, although I do not know how many of these places were actually visited without sightings having been made. One sighting [Lower Earley] was in an Asda car park in a built-up area about 1 km from the nearest woods. Two of the 22 localities were in the Chilterns [three last year]. I do not count Moor End Common; although it is in the Chilterns, it is not a typical downland wooded area.
- There were also several 'new' habitats ['new' habitats means, simply, that we do not have records from these places from recent years]: Ham/Home Wood, Arncott Wood, Bagley Wood, Watlington Hill and Ashridge Park [there was an unconfirmed report from Ashridge last year]. I do not count the Asda Car Park sighting as a new locality [made, incidentally, by a very experienced Hants observer, Ashley Whitlock]!
- Several localities which produced sightings in previous years were negative this season. Most notable is Piddington Wood, where what appeared to be an excellent territory [a glade bounded by Oaks and Ashes near the south-eastern high point edge] was deserted this season.
- Territories/male assembly points. Apart from Piddington, mentioned above, and Greatsea Wood high point, all the territories described in previous reports were occupied. Worth singling out is the south-eastern edge of Little Wood where a very large Ash and several big Oaks stand at a ride junction. Five visits were made from 29.6 to 18.7, and 12 sightings were recorded around the same group of trees. It was gratifying to note that sightings were made at the Boarstall Wood territory again.
- First specimens seen on June 29th, the last on July 27th, a somewhat shorter season than usual.
- We still lack observers in Berkshire. David White did a splendid job in Windsor Forest, but, apart from the 'rogue' sighting in Lower Earley and a sighting by Andrew Bolton in the extreme south west corner of Berkshire in Combe Wood, we had nothing else from that county.
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| A. iris observations 2005 (data from Levana) | A. iris observations 2006 (data from Levana) |
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| A. iris observations 2007 (data from Levana) | A. iris observations 2008 (data from Levana) |
3. Results and Discussion
3.1 Weather
I'm grateful again to Matthew Oates who kindly supplied me with his weather diary for the critical period, as follows:
June 2008 was unmemorable, for neither good nor bad reasons. After a
poor first three days (the 3rd was vile) it was reasonably dry and produced a good scatter of fairly
pleasant summer days, though nothing special. The second half was unusually windy and saw a lot of cool
nights, though with several quite sunny days. The whole month was fairly dry, bar heavy rain on the 3rd and
22nd, which produced an autumnal gale.
July 2008 started promisingly but fell from grace spectacularly, and was excommunicated early. The
month had twice the average rainfall and would have been unusually cold had it not been for the nice weather
of the 3rd week. July 1st was sublime and suggested a great month. A deep depression edged over on the 5th
producing an autumn gale on the 6th, which undoubtedly decimated in sensus hodierni arboreal butterflies, notably
His Imperial Majesty (something similar happened in 2004). 1" of rain fell on the 6th, another on the 7th, and
yet another on the 9th. The weather then went into cool and cloudy mode, with cool clear nights and convective
cloud bubbling up in early morning, allowing only a few random sunny breaks. There was a nice day on the 13th,
but the 3rd week of July was again dominated by cloud, though with only a little rain. Cold nights were again
a feature. All this effectively terminated the Purple Emperor season - and the weather immediately improved:
a good anticyclone came over for the 4th week, giving temps in the high 20s and almost breaking the 30dC barrier.
A massive thundery breakdown occurred on the 28th, producing localised heavy thunderstorms (1" of precipitation
in 30 mins at Culkerton) and the month ended poorly. July: you owe us.
3.2 Sightings
Although the weather was generally poor, the sightings were up on last year, but still well below the excellent 2006. I intend to look more closely at the data and try to normalise the number of sightings for each year with respect to the factors which have an influence, i.e.: number of observers, number of different localities visited, number of visits. Clearly, we cannot draw any sound conclusions about 'good' and 'bad' years unless we take these factors into account. The first observation was on 29th June, which is a few days later than average; perhaps due to the poor June. The season was undoubtedly affected negatively by the relatively poor weather at the height of the season: the middle two weeks of July. This was reflected by the sightings: from June 29th until July 5th [good weather], there were 37 sightings in 17 visits [=2.2 sightings/visit]; on July 6th and 7th the weather was awful, I had no reports from these two days; July 8th till 14th [moderate to poor weather], 27 sightings in 17 visits [=1.6 sightings/visit]; July 15th till the 27th [weather moderate to poor], 18 sightings in 12 visits [=1.5 sightings/visit].
3.3 Distribution
See maps above. We are still suffering from too few observers in Berks. Oxfordshire was as good as Bucks this year.
3.4 Territories [male assembly areas]
- Oakley Wood Car Park. Very poor; only one report [5th July] when 4 sightings were made in the car park area, i.e. none around the trees near the entrance, which was so good two years ago. Most of the sightings in this forest were spread over Shabbington Wood, Yorks Wood, and Hell Coppice, with no obvious territory being identified.
- Piddington Wood. The 'vista', or glade, discovered by the Campbells two years ago, was surprisingly deserted. There is no obvious reason, apart from a tree in the middle which has grown considerably, possibly obscuring the general view.
- Little Wood. At the point where the path along the south-eastern edge meets the top of the central ride going down through the wood, there is a very large Ash and several Oaks. This was very good [again] this year [see summary], and seems to be the main territory in this area.
- Finemere Wood. The Ashes at the northern end were again not as good as two years ago; some activity, with just a couple of individuals on two separate occasions. The 'central territory', namely the stretch of ride [about 200m] running south of the turning circle to the next ride junction was quite good, with a number of people making sightings along this stretch. Seven sightings were made on four different occasions.
- Greatsea Wood. Nothing at the high point.
- Rushbeds. Sightings again on the Ashes just inside the wood along the main ride just before it exits into Lapland's Farm meadow. We never see many here, but it is regularly used, every year.
- Boarstall Wood. Sightings were made again, after an absence of a couple of years, above the Ashes behind the cottage from the eastern end of the path skirting along the northern edge, by the road.
3.5 'New' habitats
This was a good year for 'new' habitats; no less than five were noted. Perhaps the most
gratifying of all was a private wood which is part of the Bernwood remnants in Bucks. The owners are very keen and were always
disappointed that they had never seen iris in their well-managed wood. They were not satisfied that they have
one the best pruni woods of all! We too, were always 'unhappy' about the lack of HM here, because only about
1km to the north there is a good population in a private wood in the Grendon area and, a bit further to the
south, we also see them regularly in Rushbeds Wood, so there is no obvious reason why iris should not inhabit
this wood: there is plenty of Sallow and mature Oak and Ash. Well, the owners, finally, had a bitter/sweet
experience; they told Dave Wilton that they had run over a male on fox droppings while driving down a main ride in the wood
[4th July]! On 11th July, Dave had a sighting in a different part of the wood. This is great news, because,
apart from Tittershall [which we can't enter], we now have the records to show that iris inhabits all the
woods comprising the 'Bernwood remnants' from Waterperry/Holton running along a north-east axis to Claydon Woods.
Dave Wilton and Stuart Hodges saw a female in a clearing in Arncott Wood, which is on MOD land, quite late on
in the season. Arncott Wood, together with Little Wood, Oldhouse Spinney, Piddington Wood, and the area
between Little and Arncott Woods [no name on the OS map, but also on MOD land] form quite a large woodland
complex, and it highly likely that iris flies from one wood to another. There is a vast amount of Sallow in
these woods.
David Redhead, while exploring the grounds of the Westwood Country Hotel at the northern end of the privately owned
Bagley Wood,
observed activity at the tree tops from the hotel's grounds. There are past records from this big wood, but
nothing recently.
On the same day, David also had a sighting on Watlington Hill, demonstrating, again, how widespread
iris is in the Chilterns, although we hardly ever see more than one or two per visit.
In recent years, we have had unconfirmed reports from Ashridge Park, in the area of the monument.
This season, we had a definite sighting there by Dave Maunder on July 27th. A friend of Ched George
also told him about a sighting at the same spot on July 19th. Whereas Dave's sighting was definitely
[just] in Bucks [SP972131], the July 19th sighting was in Herts [SP975129]. This then is another
new Chilterns site.
3.6 Observations away from woodland
Only one this year, with a possible second. Asda Car Park at Lower Earley [SU743701]. Looking at the OS map, you can see small woods or copses about 1km away from this spot. One to 1.5 km to the south, between the River Loddon and the M4 motorway there are several copses close together; iris would have to negotiate the M4 and a built up area to reach the Tesco car park; no mean feat!
The second possible site is intriguing. It is a group of Oaks at the edge of a school field, not part of a wood but quite close to a large wood on the edge of Burghfield Common, Berks. The observer could, from his garden, see 'large butterflies' flying around these Oaks throughout July from late afternoon onwards. We have been invited to visit this spot next season.
3.7 General
Apart from the 'usual habitats', sightings were made by the Campbells in woods
which are not frequented by many of us: Sydlings Copse, Holton Wood, Boarstall Wood, and Stanton Great
Wood [the latter only from the edge; it seems that access is not permitted]. Dave Wilton also covered
a lot of ground and was rewarded with two new habitats [Ham/Home Wood - access by permit only - and
Arncott Wood]. Our chairman, having complained in the past about 'rarely seeing iris', had a
good year. In particular, on July 21st, he made sightings in two 'new' habitats, quite far apart,
Bagley Wood and Watlington Hill. In addition, during the field meeting on July 5th in Bernwood, he
returned to the Oakley car park before the rest of us and made 3 sightings! David White, 'our man in
Berkshire', has visited Windsor Forest over a long period, and first saw HM there in the nineties.
This year, he spent a lot of time during several visits trying to understand better the lay of the
land in the territory he had discovered years ago. The territory is a ridge in the northern part of
the forest, whereby a view of the tops of the trees at this high point is mainly obscured, resulting
in only brief sightings. Due to some felling, this ridge has become more exposed, so he investigated
more sheltered areas lower down, and was successful [see Appendix for details]. Access to this royal
forest is severely restricted, by the way: you need a permit.
Richard Soulsby had, probably, the best experience of all; during a visit to Finemere, late in the
season, he was privileged to watch three specimens at sap on an Oak branch in the main territory just
south of the turning circle for about 30 minutes. However, I subtracted any brownie points he had
earned, because he did not have a camera with a zoom with him, so he failed to record this experience!
4. Conclusions and plans
- A reasonable season, considering how poor the weather was.
- Most positive result was the discovery of 5 new habitats.
- Disappointing, but intriguing, was the lack of sightings in previous territories.
We should continue to study behaviour on territory, and look in previously unexplored woods. I reproduce here part of a table I used for the 2004 report; this shows woods from which I've had no reports since 2004.
| Wood | English Nature Site records (Year) |
Levana (Year) |
| Baynes and Bowdown reserve | 1989, 1990, 1994, 1996 | |
| Blackmore Wood | Ched George 1995 | |
| Blackwater and Stanton Little Wood | 1982 | |
| Brasenose and Shotover Hill | 1986 | |
| Burnham Beeches | 1991 | |
| Bussock Woods btwn Newbury and M4 | 1991 | |
| Coombe & Buttermere (s. of Bagshot) | 1991 | |
| Crowell wood | 2002 | |
| Denford Park | 1998 | |
| Greenfield Wood | Ched George post 1996 | |
| Hatchet Wood | 1997 | |
| Holly | 1985 | 1985 |
| Home | Pre-1905 | |
| Howbery Park | 2001 | |
| Howe Park | 1959 | |
| Kingwood Common nr Sonning | 1991 | |
| Leckhampstead and Wicken (N .Bucks) | 1986 | |
| Leckhampstead Thicket (W. Berks) | 1987 | |
| Nettlebed | 1989 | |
| Queen Wood nr Watlington | 1990 |
It would also be useful to continue to explore the Chilterns, the most fruitful area seems to be the large expanse of forest to the east and south-east of Risborough [sightings by Ian Kelloway and Francis Gomme a few years ago]. I spent time exploring some of the high points here last summer without success, but it is a 'needle in a haystack' job. I'm sure they are there. David Redhead showed that we always have a chance of seeing HM anywhere in the Chilterns.
The Milton Keynes Natural History Society has been looking in the considerable expanse of woodland straddling the Bucks/Northants border, but no luck so far.
Here is some useful literature:
- 'The Ecology and Conservation of the Purple Emperor', published in 1987 by Ken Willmott, which was a project supported by the WWF. Ken has continued to study iris ecology in his wood [Bookham Common, Surrey] since then, and has accumulated a wealth of ecological information.
- Matthew Oates has coordinated a national iris project during the last few years and has published reports on the findings. He himself has accumulated an enormous amount of knowledge from his observations over many years, mainly, but not only, in Alice Holt Forest.
- Elizabeth Goodyear and Andrew Middleton have coordinated iris observations for the Herts/Middx section of BC during the last few years and have also published excellent annual reports.
Dennis Dell
October 2008
