BUTTERFLY CONSERVATION UPPER THAMES BRANCH

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Purple Emperor (A. iris) Report for 2007

Dennis Dell

Purple Emperor m.
Photo © Wendy Wilson

Acknowledgements

I’m very grateful to the following [not all of them UTB members] who submitted reports:

Wendy & Mick Campbell; Richard James; Ashley Stow/Louise Stratford; Martin Kincaid; David Redhead; Dave Wilton; Ina Wallace; Becky Woodell,; Gerry Kendall; Stuart Hodges; Nicola Chester; Sue King; Tom Dunbar; Ched George; Nick Bowles; Dave Ferguson; John Ward-Smith; Graham Elcombe.

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 bottom of page). 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. For example, the Campbells had zero sightings on 9 of their visits and Graham Elcombe responded to my request last year to visit woods so far unexplored by visiting eight spots in the Chilterns and, particularly, woods around Beaconsfield, without any luck.

2. Summary

• Sightings were made at 17 localities. Last year, the figure was 30, although I do not know how many of these places were actually visited without sightings having been made. Three of the 17 localities were not woods: Easthampstead Conference Centre, near Bracknell, which is about ½ mile from the nearest wood; Farmoor reservoir, about ½ mile from Wytham Gt Wood; Garden at Upper Green, about ½ mile from Inkpen Common Wood. Three of the 17 localities were in the Chilterns [six, last year].
• About 55 sightings were made [last year it was 130].
• Territories/ male assembly points. Since the overall sightings were well down on previous years, few were seen at established territories, i.e. the ‘Piddington Vista’; the northern edge of Finemere; the Oakley Wood car park; the ash canopy gap on the northern edge of Rushbeds; the high point at the eastern edge of Greatsea. Possible new territory: large Ash tree at highest edge of Little Wood.
• ‘New’ habitats [‘new’ habitats means, simply, that we do not have records from these places from recent years] were: Inkpen Common area; Ashridge Park; Bracknell Forest area [Easthampstead].
• First specimens seen on June 19^th, the last on August 10th.

A. iris observations 2005 (data from Levana)

A. iris observations 2006 (data from Levana)

A. iris observations 2007 (data from Levana)

3. Results and Discussion

3.1 Weather

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

April: an exceptionally warm month, with new April records for max. and mean temperatures [max temps over 5 degrees C above the 61-90 average]. Rainfall below average.

May: a wet month with some areas setting new rainfall records for the month. Mean temperatures above average, despite sunshine amounts below normal.

June: A warm and dry start, becoming increasingly unsettled. Mean temperatures generally 1 deg C above average. Well above average rainfall; some areas had their wettest June on record. Sunshine amounts below average.

July: Mean temperatures close to or slightly below average. Max temps below average. Rainfall well above average [about double the normal].

Summary: Mean temperatures about normal. Rainfall well above average.

3.2 Sightings

Well below that of the last few years and this reflects the general experience in other regions where iris is regularly observed. The first observation on 19^th June is about one week earlier than normal, possibly due to the very warm April weather, which may have accelerated larval development. However, this early emergence was not continued, and there was a definite lull in sightings until about mid-July. Maybe the higher than average rainfall influenced this. Only on 9 occasions were more than 1 specimen observed. The 14^th July in Bernwood Forest bucked the trend, when about 13 individuals were seen. It has to be said that about 20 people were observing, split into two groups who were in different places during the day; obviously, having so many pairs of eyes looking, increases the chances of sightings. Nevertheless, in previous years during the same field meeting with the same numbers of observers present, not so many iris individuals were seen.

On July 10^th, four of us watched 3 specimens cavorting around a huge Ash at the top edge of Little Wood for about 30 minutes. Interestingly, 8 days later, the Campbells also saw 3 at the same Ash tree. They also confirmed Sydlings Copse [BBOWT] as a good habitat, having seen 4 there on July 14^th, as well as Moor End Common, Frieth, where they saw 3 on July 22^nd. The latter is a very interesting wood; although it is in the middle of the Chilterns, it is predominantly acidic and has an excellent deciduous mix with many fine old Oaks.

The last sightings were on August 10^th, at two locations far apart from each other. This suggests a somewhat longer season than usual [about 51 days] and emergences extended over a longer period, perhaps because of the heavy rainfalls.

3.3 Distribution

See maps above. We are still suffering from too few observers in Berks and Oxfordshire. Not surprisingly, in this relatively poor year, the number of 2km squares is down on previous years. However, the two Berks squares are new [see later].

3.4 Territories [male assembly areas]

1. Oakley Wood Car Park. Very few observations, even in Bernwood on July 14^th when 13 were seen altogether, but only 2-3 in this car park.
2. Piddington Wood. Also very few observations at ‘the vista’.
3. Little Wood. Several have been seen along the top edge in the last few years. This year a very large Ash was favoured, with observations being made by different people 8 days apart.
4. Finemere Wood. Very poor this year. Only one seen along the Ashes at the northern edge.
5. Greatsea Wood. At the same high point as in previous years, 2, 1, and 1 seen on July 9^th, 12^th, and 24^th, respectively.

3.5 ‘New’ habitats [sightings away from woods not included]

Only one this year: Ashridge Park in the Chilterns. This very large forest straddles the Bucks/Herts boundary, but the observation was definitely made in Bucks. We’ve always felt that sightings ought to be made here, since there have been several from the Tring area in recent years. This is the most northerly Chilterns observation so far.

3.6 Observations away from woodland

Easthampstead Conference Centre, nr Bracknell. This specimen was seen inside the building, flapping against a window. Looking at a map of the area, the nearest wood [Big Wood] is at the end of a long avenue of trees, about ½ mile distant from the house. This is the first sighting we’ve had from the Bracknell area.

Upper Green, Berks. This was in a garden about ½ mile from Inkpen Common, from where there are old records.

Farmoor Reservoir, Oxfordshire. This is close [1/2 mile] to Wytham Great Wood, where sightings were made last year.

4. Conclusions and the future

In the same section in last years’ report, a number of questions were posed. Because of the rather poor 2007 season, none of these could be answered. I repeat here suggestions for studying this species and discovering more about its ecology:

· 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 until 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.

We may not be blessed soon with another year like 2006, but let’s hope for something better than this year in 2008.

Dennis Dell

October 2007

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

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