PURPLE EMPEROR (A. iris) REPORT FOR 2006

UPPER THAMES REGION, BUTTERFLY CONSERVATION

By Dennis Dell

© Photos of Purple Emperor by Tony Hall (left) & Dave Wilton (right)

Click photos for larger image.

Acknowledgements

I’m very grateful to the following loyal subjects of the Emperor who submitted their reports to me (36 of you, including me):

Wendy & Mick Campbell, Dave Wilton, Allen Beechey, Robin Dryden, Tom Dunbar, Ched George, Nick Bowles, David Redhead, Paul Bowyer, Dave Ferguson, Adrian Hickman, John Ward-Smith, Duncan Stubbs, Phil Tizzard, Martin Kincaid, Danny Howard, Graham Elcombe, Ian Walker, Graham Taylor, Christopher Prideaux, Giles Alder, Dick Lister, Niall Lusby, Allan Showler, Owen Lewis, Mike Mobbs, Graham Lincoln, David Dennis, Ian Kelloway, Don Otter, Francis Gomme, Jackie Tuckey, Tony Croft, Becky Woodell.

I must mention, for devotion to duty, without reward: David Fuller who paid 4 visits to Windsor Forest [where he had made sightings in 2005, and also David White over several years in the nineties], each of about 4 hours duration without sight of his Royal Eminence!

Several of these observers were not known to me previously, but had: 1) sent their observations to Wendy’s sightings page on the website, or, 2), had sent their sightings to several members who then put me in touch with these new observers. I am grateful to all of you. This is what networking is all about, and, for me, is a very positive aspect, because it has widened the circle of people I can turn to for data.

1. Introduction

As in previous reports, the observations in detail may be found in the Appendix. 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 their woods when they made no sightings.

2. Summary

30 localities were visited, of which 5 were areas distinctly outside woods, but not more than about 1 km from the nearest wood [i.e., a golf course [1], and in or near villages or at the edge of a town [4]]. Of the remaining woods [25], 6 were in the Chilterns.
About 130 sightings were made.
Territories/ male assembly points. The ‘Piddington Vista’ was confirmed, but with not as many sightings as last year. The northern edge of Finemere is definitely a territory. Again, the most populated territory was the Oakley Wood car park. An ash canopy gap on the northern edge of Rushbeds was occupied again, but apparently not by more than one or two males. The high point at the eastern edge of Greatsea was frequented by several individuals for the third year running. The tall poplars at the southern end of Waterperry [‘Drunkard’s Corner’] were once again not used.
‘New’ habitats [‘new’ habitats means, simply, that we do not have records from these places from recent years] were: Little Hazes Wood Berkshire; Wytham Woods Oxon, Penn Wood Bucks; Downley [ High Wycombe], Buckland Common Bucks; Sole Common Berks; Moorend Common nr. Frieth Bucks; Braziers End Bucks; Hodgemoor Wood Bucks; Leygrove’s Wood Bucks; Widnell Lane Oxon; Murcott Village, Oxon.
First specimens seen on June 25^th, the last in mid-August.

A. iris observations 2006

A. iris observations 2005

These two maps probably reflect, in the main, an increase of the number of members ‘looking’ and the number of places visited from 2005 to 2006.

3. Results and Discussion

3.1 Weather

The BBC Weather internet site is the source of the following information.

May: above average mean temp., well above average rainfall, and average sunshine hours.

June: well above average temperature, very low rainfall, and above average sunshine hours.

July: the temperature was in the ‘exceptionally above average’ category, as was the total sunshine hours; the rainfall was well below average. Previous sunniest month was June 1957.

June and July, therefore, provided exceptionally fine and dry weather, which may have accounted for a slightly earlier than usual emergence.

The following is Matthew Oates’ summary:

March was cold and April dry and cool. Purple Emperor larvae did not commence feeding until the end of April.

May was the wettest since 1979 and one of the wettest ever. The first half was very promising but wet weather set in on the 15^th and it remained wet until the last two days. Evenings during the second half of the month were mostly unsuitable for feeding Purple Emperor larvae.

June was sunny, dry and warm, with a series of anticyclones from the Azores. There was only one wet day (the 26^th). Purple Emperor larvae were able to pupate quickly and the insect probably spent a relatively short time in the pupal state.

July began with an intense anticyclone which saw temperatures around 30dC. This ended with a thundery breakdown on the 5^th-6^th, with heavy downpours in most parts of central southern England. The weather was rather indifferent between the 7^th and 10^th (inclusive), with limited flying opportunities due to cloud and / or wind, but another intense anticyclone developed on the 11^th, again from the Azores. It was virtually cloudless from the 11^th to the 21^st (inclusive), apart from a weak front on the 13^th, with temperatures above 25dC on each day throughout the Purple Empire during this period. On five days the temperature exceeded 30dC, with an all-time record July temperature of 36.5dC at Wisley (Surrey) on the 19^th. During this period Purple Emperor activity was heavily suppressed by heat, and the males especially burnt out rapidly. Thunderstorms broke out widely on the 22^nd but another anticyclone promptly developed, though the weather collapsed during the last two days of the month.

July was the hottest month on record in the UK, beating July 1983 and August 1995.

3.2 Sightings

Similar to last year. Although this species is apparently quite widespread in our region, the number of sightings are certainly lower than those in two prime localities, Fermyn [Northamptonshire] and Alice Holt [Hampshire] Woods.

3.3 Distribution

In most of the areas where members went to look for iris it was found [see maps above], indicating that its status in our region is quite healthy. However, there is a lack of observers in most of Oxfordshire, large parts of Berkshire, and North Bucks, which might explain the absence of sightings there.

3.4 Woods in which sightings were made and suggestions for woods to be visited

^{WOODS VISITED IN 2006}		^{*WOODS TO VISIT IN THE FUTURE} ^{(see note)}
BUCKS		BUCKS
Black Park	TQ0184	High Scrubs	SP9208
Finemere Wood	SP7122	Dunsmore	SP8505
Doddershall Wood	Private	Monkton Wood	SP8301
Rushbeds Wood	SP6615	Park Wood	SU8298
Greatsea Wood	Private	Great Wood	SU7686
Penn Wood	SU9095	Leckhampstead Wood	SP7240
Wendover Woods	SP8807	Tilehouse Wood	SP6839
Woodland near Frieth; Moor Common	SU8090	Whitfield Wood	SP6439
Chinkwell Wood	SP6614	Park Copse	SP7338
Hodgemoor Wood	SU9693	Beachampton Grove	SP7836
Woods just east of Princes Risborough	SP8203	Woods on south-western edge of Milton Keynes	Oakhill, Shenley, Howe Park, Thrift, Broadway
Leygrove’s Wood	Private
BERKS		BERKS
Sole Common	SU4170	College or Abbots Wood	SU6580
Warburg reserve	SU7287	Nettlebed Woods	SU7086
Little Hazes	Private	Hermitage	SU5171
OXON		OXON
Piddington Wood	SP 6216	Ash Wood	SP5118
Yorks Wood	SP6120	Bagley Wood	SP5102
Waterperry Wood	SP6009	Fernhill Wood	SP6504
Whitecross Green Wood	SP6014	Coombe Wood	SP5904
Sydlings Copse, BBOWT reserve	SP5509	Roundhill Wood	SU5597
Hell Coppice	SP6110
Little Wood	Private
Wytham Woods	SP4608 (permit reqd.)
Oakley Wood	SP6111
Holton Wood	SP5907

*Please note: These woods have not been checked for public footpaths and

might not be accessible, therefore, without prior arrangement with the owner.

The ‘woods to be visited’ column is just a suggestion; any woods in our three counties which have not been investigated could be added.

3.5 Territories [male assembly areas]

Oakley Wood Car Park. More seen here than last year. Most of the activity was on and around several Oaks and a Poplar just inside the main entrance from the road, on the right as you enter. This is the high point of the whole woodland complex, although the elevation range, from 60m at the southern end of Waterperry Wood to 90m in the Oakley Wood Car Park over a distance of 3.5 km, is modest. The 9^th of July there was interesting; the weather was not ideal, with a strong wind blowing [3 to 4 on the Beaufort scale], but this did not seem to deter flight activity; on one occasion, three were in the air at the same time.

Piddington and Rushbeds. It is difficult, sometimes, in the UT region, to know for sure whether a particular area is a territory or not, because of the low numbers encountered. In so far as more observations have been made at a particular spot in both of these woods, two years running, we may conclude that we have identified territories. In Piddington, the ‘vista’ [see Appendix] is along the highest point in this wood. Rushbeds, however, is rather flat, and the Ash canopy gap at the northern edge represents neither a high point nor trees which are significantly higher than neighbouring trees [unlike the poplars at Drunkards Corner in Waterperry Wood]. Maybe a suitable canopy gap is also sufficient to encourage assembly behaviour.

Finemere Wood. A 300m stretch of the northern edge, running along the 115 metre contour line [the highest point in the wood], consists almost entirely of Ash trees with suitable ‘canopy gaps’ at intervals. Some observations were made here last year. This year, a number of observations were made over several July days. In particular, two people made two separate visits about 2 hours apart on July 12^th, and each saw 3-4 specimens at different canopy gaps about 200m apart. This is intriguing and poses the question as to whether iris might occupy different, but suitable, canopy gaps and migrate between them during the course of the day. Experienced friends [Matthew Oates, Elizabeth Goodyear] have observed movement within territories during the day according to weather/angle of sun.

3.6 ‘New’ habitats

We have continued to extend our searches to areas which have either never been investigated for this species, to our knowledge, or certainly not in recent years and have been rather successful.

· Penn Wood Bucks, and surrounding area: One of our members has been a regular visitor to this wood, now owned by the Woodland Trust, over many years, and 2006 was the first time he had seen iris here. Observations were made on four separate days, including mid-August [supported by a photo], which was by far the latest observation.

· Little and Great Hazes Wood, Berks: This adds to the few records we have from Berks. This is a small wood very close to and bisected by the M4. The sighting was made adjacent to a trout farm fishery. There are several small woods close by which would be worth investigating next year. The nearest known locality [but no sightings this year] is Windsor forest, about 7 km to the east.

· Wytham Woods, Oxon: Sightings were made on two days early in July. The large woods around Oxford should be home to iris but we lack recorders.

· Sole Common, Berks: This observation was quite close to the BBOWT reserve [pond] and was only the second one from Berks this year. It is by far the most westerly sighting in our region.

· Moorend Common nr. Frieth Bucks: Four specimens were seen within 15 minutes. This is a very small wood, full of Sallow. It is surrounded by a network of other small woods, all close by. Observations have been made in gardens in Frieth, adjacent, in recent years.

· Hodgemoor Wood Bucks: This was an important sighting, since there are no records from this area [Chalfont St Giles]. It is about 6 km south-east of Penn Wood. It is the most easterly record we have so far.

3.7 Observations away from woodland

· Downley: A female was seen on the ground in this village on the north-western edge of Wycombe. The nearest woods of any size are about 2km away.

· Buckland Common Bucks: Male seen on the windowsill of a house in the village, which is about 1 km from the nearest wood.

· Braziers End Bucks. In a garden, about 1 km east of the above sighting. Even further from the nearest wood.

· Murcott, Oxon. A worn male [25/7] settled on the observer’s hand for along time. Proboscis out. This village is about 1.5 km north-west of Whitecross Green Wood, a known habitat.

· Widnell Lane, Oxon. This observation [27/7] was about 1km north-east of Piddington Wood, a known habitat, probably a female.

4. Conclusions and the future

This species is more widespread in the UT region than we had perhaps thought up to about three years ago. It is very gratifying to have discovered more habitats in woods on the Chilterns from year to year., although the main centres of population still appear to be in the remnant woods which comprised part of the old Bernwood Forest.

The several observations 1 km or more away from the nearest wood with a known colony are interesting. It is known from the literature that iris will wander away from its ‘home wood’. We do not know, of course, whether any particular specimen engaged in this ‘extra-arboreal’ activity is merely making a temporary excursion outside its wood, or whether it is extending its range.

We need to have more observers in Oxfordshire, Berkshire, and North Bucks, in order to ascertain how widespread iris really is in the UT region. The Sole Common and Hodgemoor wood sightings were the most westerly and easterly, respectively, so far, and these are fairly isolated from other localities. This suggests that we will find it in many more woods in these, so far, little explored areas.

It is gratifying to note that iris is doing quite well in woods which are managed for nature’s benefit and which may, therefore, be considered as ‘safe havens’ [e.g. Whitecross Green, Oakley, Shabbington, Waterperry, Rushbeds, Finemere] from which the species may extend its range. We also have one private wood [Grendon/Doddershall] where the owner is very keen on his butterflies [especially iris] and has an English Nature grant to encourage him.

The ecology of iris has been a source of fascination for many entomologists. Its movement within a wood during the course of the day, and the tendency of the males to congregate in certain places has always intrigued us, and continues to do so. The predilection of the males to assemble at high points or around the highest trees is well established, and we are now studying behaviour at the high points: when does it commence? Are particular trees/groups of trees favoured? How is it affected by time of day and the weather? Why are some high points deserted after some years? Do these assembly points have to be near to concentrations of Sallow? Dialogue with friends from different areas of the country suggests slightly different behaviour from wood to wood.

Some of you might like to try to answer some of these questions. It would mean:

· concentrating on a wood of your choice where iris is always seen

· visiting the wood every three days [if possible] during the flight season [from about June 25^th till the end of July], and only in reasonable weather

· observing for at least 30 minutes in particular areas of the wood at ‘likely’ micro-habitats; these are well known to you:

a] groups of trees at high points

b] groups of the tallest trees where the wood is largely ‘flat’

c] glades, or areas where the trees are spaced about 20 metres apart [perhaps as the result of recent felling]

d] anywhere along wide sunlit rides

e] woodland edges, especially where there are gaps in the canopy

f] car parks within or at the edges of the wood

g] groups of Sallows [to observe female behaviour].

If you identify a ‘good’ territory, then pay several visits to this area at different times of the day to monitor any changes in activity/behaviour/numbers seen.

Very useful sources of information are:

1) ‘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.

2) 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.

3) 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.

· Click here to see the Appendix: “Details of sightings”

· Top of page

~ o0o ~