BUTTERFLY CONSERVATION UPPER THAMES BRANCH

Back to Species Champions

Purple Emperor (A. iris) Report for 2009

Dennis Dell

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 6 years, we have built up a large network of observers. I apologise if I've left anyone out in the Appendix.

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

We have a prophet in our midst: David Redhead. On July 2nd he sent an e-mail to members to remind them of the A. iris field meeting on the following weekend. His first words were: "In years to come people may well ask: 'In 2009 were you in Bernwood Forest on 4th July...?'"

Indeed, this was an extraordinary day ... I've never experienced anything like it in our region [details later].

• 2009 was by far the best season for the Purple Emperor in our region since I've been back in the UK [from 2003].
• About 222 sightings were recorded [last year it was 82], at 29 localities.
• 8 'new' habitats were found ['new' habitats means, simply, that we do not have records from these places from recent years].
• Territories/male assembly points. Established territories in Little, Oakley, Rushbeds, Finemere, Boarstall, Piddington Woods and Sydlings Copse were occupied again. Possible new territories at Piddington and Shabbington Woods and Shotover Country Park were noted.
• First specimens seen on June 25th, the last on July 31st.

A. iris observations 2005 (data from Levana)	A. iris observations 2006 (data from Levana)

A. iris observations 2007 (data from Levana)	A. iris observations 2008 (data from Levana)

A. iris observations 2009 (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 [I have not edited this, because I want you all to enjoy Matthew's inimitable style]:

February 2009 was interesting. No rain fell all month (apart from sleety stuff intermingled with snow). The first 12 days were very cold with five snow falls, notably on the nights of the 4th and 6th, and frosts every night. Then mild weather slowly edged in from the 13th, bringing a slow melt. From the 15th it was very dry and fairly mild.

March 2009 was remarkably dry, with <1" of rain all month, falling on only four days (and mainly on the 3rd). It began with a two day anticyclone, which I regard as a sign of a good March. Both the Azores and Scandinavian high pressure areas were active all month, producing four fine spells, the best of which was a lovely week from the 14th to 21st, which saw butterflies properly active for the first time in the year. Prior to then temperatures had been just a bit too cool. Nights were often frosty, and there was a cold spell towards the end (27th and 28th), before the month ended mild and grey. Apart from a windy spell late on, it was a remarkably calm month.

April 2009 was good, notable for a lovely first three days and a sublime spell between the 19th and 24th, and a scatter of other good days and part-days. It wasn't particularly dry, with some spells of heavy rain (6th, 10th, 18th and 27th), and there were quite a few cold nights, especially the night of the 27th). Cold nights probably hindered butterfly emergence and day temps were never high (the month's max was 19C) and often only moderate (lots of days of 13-14C tops).

May 2009 got excommunicated for the usual reasons, though it ended well. It started reasonably, but then fell apart on the May Day bank holiday, Mon 4th. The middle two weeks were cool, cloudy and windy, though without the precipitous rains of recent Mays. Things started to improve on the 21st, mainly because I bundled the foul & abusive weather into the boot of my car, and transported it back to Wales, from whence it had escaped. I locked it in the Black Mountains, where it belongs. The last week was good, and we even had a good Whitsun bank holiday Monday, but that was too late for the early spring spp. like Green Hairstreak, Dingy Skipper and Duke of Burgundy Fritillary, which had been blasted away. Marsh Fritillary and Pearl-bordered Fritillary held back and made the most of the late May anticyclone. I'm not having May next year, it's banned; instead I'm having 31 days of 31st June, from 1953 to 1984.

June 2009 was mixed. It started and ended superbly. The first four days were great but there was then a cold dull spell from 7th-12th, followed by some mixed weather. The 16th was good and from the 21st the weather became increasingly hot and sunny, and June ended wondrously. Rainfall was probably average at best. The daily maximum temperatures ranged from 30C (30th) to 12C on the 8th and 13C on the 6th. It may be this cold spell that triggered aberrations in paphia, c-album and iris.

July 2009 fell spectacularly from grace. The first two days were sublime but the jet stream jumped south on the 6th and the rest of the month was, in a word, vile. After the 5th we had only three good days (10th, 16th and 25th), though some others were workable (e.g. 12th, 14th, 23rd, 27th, 28th & 31st). It was a very wet July in most districts, though not the extreme SE. Bristol had its wettest July since 1888.

3.2 Sightings

We recorded over twice the number of sightings [220] compared with any of the previous six years. I asked our colleagues in the other good A. iris counties [Surrey, Sussex, Hampshire, Wiltshire] and they tell me that their season was maybe a little better than average. Northamptonshire was better than average, with sightings made [Doug Goddard] in seven woods other than Fermyn Forest [where Matthew Oates observed very large numbers]. Hertfordshire was about average.

The good season in UTB cannot be due to the weather during the critical months for larval development to maturity, namely April and May, since, although April was good, May was poor on average. The fine weather during the last week in June and the first five days of July was almost certainly an important factor for the high number of sightings then, even during the rest of July when the weather disappointed, the numbers seen were still better than in previous years.

June 25th for the first sightings is 'normal', as is end of July for the last sightings, although I'm surprised that we saw none at all in August.

This chart has to be interpreted with caution. Obviously the number of sightings depends on many factors, e.g. the number of observers, the suitability of the habitats, the weather, the date, time of day. The total number of sightings [blue, y axis] was divided by the number observers. The latter ratio [purple] gives a different picture and does not change what we already know: namely, that the first two weeks of July are the best time to look for A. iris. The very fine weather at the end of June encouraged people to go out and look, with the result that 18 people made 23 sightings, certainly better than average for the last week in June. The fine weather continued into the first 4-5 days of July, but this did not last for the rest of the month, apart from a few days. However, experience has shown that A. iris will fly, even when it is not particularly sunny, as long as the temperature is in the late teens and it will even fly in quite a strong breeze.

From the 1st until the 5th of July 57 people recorded 102 sightings in 18 different localities.

July 4th

During the iris field meeting in Bernwood Forest on 4th July, 18 participants made 18 sightings. About half of these were along a few hundred metres of the main track leading up to the Shabbington turning circle. The party had, as usual, divided into two, with half going up to the turning circle and the others parting company at Piccadilly Circus and going to Hell Coppice via Yorks Wood. In previous years the latter route had always produced the most sightings but this year only one was seen along this way - a complete reversal. This experience emphasises the importance of observers exploring as many different habitats in a wood during a visit as possible. Most remarkable, though, were Dave Wilton's experiences on the same day in Kingswood and private woods in the Grendon area: before midday, he saw 3 in Kingswood; from 2 until 4 pm in woods in Grendon he made 16 sightings, including three on one Oak leaf. Before 2009, no more than 5 in one day had been seen in these woods. In the same wood, before midday on this day, Nick Bowles had seen 5 along just one ride. So, on July 4th, 42 sightings were recorded by 21 people.

July 5th

The second day of the Bernwood field meeting on 5th July, in poorer weather than on the first day, produced 10 sightings by 10 observers, giving the same ratio sightings/observers as for Bernwood on July 4th.

Other noteworthy results:

5th July: the Campbells had 9 sightings in Piddington Wood, 4 at a new habitat [see below]. On the 10th July, they made 12 observations, equally split between Stanton Great and Stanton Little Woods. On the 14th July, in Chinkwell Wood, they saw 9, spread throughout the wood. In view of the rather poor weather on that day, this is extraordinary, especially as never more than 2/3 had been seen here previously. On the next day, I saw only one here!

20th July: Although nothing was seen at the Greatsea high point territory this year, lower down 2 were seen between Greatsea and Romer and 2 between Greatsea and Balmore Woods. Together with the two sightings on separate occasions in Sheephouse and one in Runts, this makes it the best year on record for Claydon Woods.

22nd July: I accompanied the Campbells and we saw 5 in Waterperry Wood - rather good for so late in the season.

28th July: A very worn female was seen by Don Otter of the National Trust at Ringshall. This is noteworthy because it is at the northern end of Ashridge park and, previously, all the sightings had been near the monument to the south, some distance away.

3.3 Territories [male assembly areas]

• Oakley Wood Car Park. Occupied on most good days, although not more than 2/3 per day. Most of the activity was confined to the car park itself where the cars proved, as usual, to be irresistible. I received no records of long term activity in the tree tops there.
• Piddington Wood. The 'vista', or glade, discovered by the Campbells, was again occupied after an absence of two years. A possible new territory was found at the south-eastern corner where sightings were made on three separate days [4 on the first day].
• Little Wood. The established territory along the south-east facing edge was again occupied, with the same big Ash and Oaks being used.
• Finemere Wood. The area around the turning circle and the Ashes at the northern edge were again occupied on several occasions. A possible new territory was discovered around the big Oaks along C section of the transect [SP721216]; several observations were made here on different days.
• Greatsea Wood. Nothing at the high point again this year, although several sightings were made lower down [see above].
• 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. Four sightings here: the best ever, with two above the Ashes behind the gamekeeper's cottage.
• Sydlings Copse. The line of trees, mainly Ashes, along a ridge above a steep drop into the valley is still a favoured spot.
• Shotover Country Park [new]. Sighting early in the morning above the Oaks at the northern end at the top of a steep slope.
• Hell coppice old car park. One male was seen in this old territory.

3.4 'New' habitats

• Langley Park. Although sightings are regularly made in Black Park, this is the first time iris has been recorded from this habitat adjoining Black Park to the south.
• College Wood. This is very exciting because this group of woods, Whaddon Chase, straddling the Bletchley to Buckingham Road, was the missing link in the chain from the northernmost habitat of the Bernwood Forest remnants, Claydon Woods, to the big woods straddling the Bucks/Northants border. It is Woodland Trust property and the warden has been alerted and is aware how important the Sallows are for iris.
• Dancersend BBOWT reserve. The first time iris has been seen in this Duke of Burgundy habitat and it represents another spot in the Chilterns to add to our records.
• Stanton Little Wood. In this small wood 6 were seen on one occasion and then 4, six days later. It is probable that iris flies freely between several woods close together here: Waterperry, Stanton Gt., Stanton Little and Holton Woods.
• Sheephouse Wood. Singletons were seen, 5 days apart.
• Runt's Wood. One female seen on Sallow at the western edge.
• Homefield Wood [BBOWT]. This is a fine habitat, and it is gratifying that iris was seen here for the first time.

4. Plans

I reproduce last year's table, showing [red] woods where observations were made in 2009. I feel sure that we would find iris in many of these other woods next year.

Again, not enough of us are searching woods in Berkshire. The lack of dots there in the distribution map points more to 'lack of observers' than 'lack of iris', I'm sure.

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

Dennis Dell
October 2009

Click here to see the Appendix: "Details of sightings"