2007 BUTTERFLY REPORT

BUTTERFLY REPORT 2007

57

2007 BUTTERFLY REPORT ROB PARKER 2007 got off to a blistering start, with seven species recording their earliestever appearances in the spring, yet a change of weather abruptly curtailed the excitement, and the year became dull, with poor showings for residents and migrants alike. Almost all recorders said what a disappointing year it had been.

Weather Although mean temperatures for East Anglia were 1·3 Deg C above historic averages, most of the extra heat came in winter and spring, (See table below) – a different pattern to 2006. After a warm, moist winter, spring was sunny and continued warm. A warm, dry April was replaced by a cool, rainy May/June, which deferred the emergence of several early summer butterflies. Summer was very wet, with sunshine below the historic average, and autumn was dry, but not as warm as 2006, and did not generate as many late butterfly sightings.

Table 1. 2007 Weather for East Anglia

Season Winter 06/07 Spring Summer Autumn

Mean Temp Anomaly Sunshine Anomaly Rainfall

Anomaly

°C

% up

hrs

%

mm

%

6·4 10·4 16·0 10·8

2·7 2·1 0·4 0·4

173·1 556·9 534·8 345·9

103 125 94 109

185·8 162 228·6 129·7

129 117 148 79

Source: www.metoffice.gov.uk/climate/uk Anomalies are measured against the 1961 to 1990 averages Monitoring the BAP Species For the second year in succession, the Dingy Skipper was not found at RAF Barnham, and the colony may have been lost, although the habitat still looks adequate. Furthermore, there were no sightings from Center Parcs either.

Fortunately the King’s Forest survey turned up decent numbers, but the overall picture gives serious cause for concern.

The Silver-studded Blue was carefully monitored in connection with a translocation to Blaxhall Common, and it would appear that the flight season started early, hesitated in the wet spell, and then continued later than usual. As a result of this spread, the totals flying at any time were low and the wet weather made it difficult to achieve good counts. Nonetheless, all sites sampled did record the species in reasonable numbers. The translocation went smoothly, but we shall not know until 2008 whether it was successful.

Trans. Suffolk Nat. Soc. 44 (2008)

58

Suffolk Natural History, Vol. 44

The White-letter Hairstreak was much more difficult to find in the poor summer than in the past two seasons, with just 23 squares recorded (5·3% of the squares visited). Over the period since 1995, records have now been made from 109 tetrads (10%), although not all of these represent established colonies, and the steady increase reflects recording effort as well as any spread of the species.

Separate detailed accounts for each of the above BAP species follow as annexes. The revision of the UK BAP species list has added four species for careful monitoring in future years: White Admiral, Grayling, Wall and Small Heath.

Residents Most of our resident species had a poor showing. Notably, the Common Blue, Small Tortoiseshell and almost all the grass feeding species declined in geographic cover, as well as appearing in lower numbers at most sites. The Skippers and Browns all feed as larvae during spring, and may not have enjoyed the hot dry April, which was followed by a wet summer to drench their flight period. To some degree, the rain also suppressed recording effort, so the result may not have been as bad as our distribution records suggest.

Despite the low numbers, several species actually extended their distribution.

Green Hairstreak, Green-veined White, Peacock and Brown Argus all did well. Meanwhile, the grass-feeding species were mainly seen in average numbers, but over an extended flight period. The declines of Grayling, Wall and (to a lesser extent) Small Heath continues, and all three have been awarded higher priority in the new UK BAP species listing. Essex Skipper, Small Skipper and Common Blue were all noted to be thin on the ground in most localities. The Red Admiral maintained its position as our most widely reported butterfly, noted from 66% of tetrads visited. The White Admiral, like the White-letter Hairstreak, suffered from the wet July; both were found in just 4·5% of tetrads visited. The Purple Hairstreak fared little better.

Purple Emperor The introduced Purple Emperors in Theberton Woods were still flying. Both sexes were seen, with a maximum of four in view at one time.

Migrants & Vagrants Some of the Camberwell Beauty influx of 2006 survived the winter, and seven singletons were noted in the spring. Whilst there was no firm evidence of breeding, another three were recorded in different locations at the end of the summer. Otherwise, the year was notably short of migrants, both butterflies and moths. Painted Lady and Clouded Yellow both put in appearances at their normal times, but in low numbers, and with only a minor surge from the subsequent generation. We had a single Swallowtail sighting, seen and photographed at Capel St Mary, and experts believe it to have been ssp. britanicus, of Norfolk origin, – a stray, rather than a real migrant. Large Tortoiseshell appeared as three singletons, in March, April and August in Cockfield, Mildenhall and Shingle Street. It is difficult to interpret these as vagrants or releases, and even more difficult to believe that the species still has

Trans. Suffolk Nat. Soc. 44 (2008)

BUTTERFLY REPORT 2007

59

a foothold anywhere in Suffolk. For the first time since 1999, Marbled White appeared in the south of the county, with authenticated sightings at Trimley on 24 June and Alton Water on 1 July. There was no sign of the Silver-washed Fritillary, which had done so well in 2006.

Early/Late Records Spring and early summer brought another sign of climate warming, with earliest-ever sightings of seven species: Small White (extraordinarily early on 21 Feb), Speckled Wood (27 Mar), Small Heath (24 Apr), Brown Argus (27 Apr), Large Skipper (21 May), Silver-studded Blue (4 Jun), and Gatekeeper (10 Jun). Then it started raining, and summer was without many good weather days, with a number of species extending their flight period later than usual.

Two of them produced latest-ever records: Silver-studded Blue (30 Sep) and Small Heath (18 Oct). It is unusual for any species to produce both earliest and latest-ever records in the same season, but both of them did this. It is worth pointing out that the Silver-studded Blue flew in a protracted single-brood, whilst the Small Heath had two broods with a long gap between them. The mild December again featured Red Admirals on sunny days, but not in the same numbers as in 2006.

Geographic Coverage Over 160 observers contributed records this year, covering 509 tetrads. 2007 is in the third 5-year block since the start of the Millennium survey and the 2005/6/7 cover stands at 776 squares, out of 1089. In other words, there are over 300 tetrads still to be visited in the next two seasons. Maps showing “black holes” are being distributed to help recorders to visit as many as possible.

Species Maps Distribution Maps for individual species have been prepared for our 31 regulars, and these are available for reference as required. This year’s total species count stands at 36, including the introduced Purple Emperor. The average number of species recorded per tetrad was 9·1, marginally below the 2006 figure of 9·4 (adjusted by late records).

Analysis Only 36 species put in an appearance this year, and these are shown in Annex A, in order of scarcity, with a direct comparison to last year’s turnout. Green Hairstreak, Brown Argus, Holly Blue and Peacock all improved on last year’s percentage cover. Those that did notably worse were Dingy Skipper, Whiteletter Hairstreak, White Admiral, Wall, Purple Hairstreak, and less predictably, the Common Blue. The Red Admiral retains its pole position as the County’s most widely recorded butterfly. The change from last year to this is expressed in the “c.f. last” column, and it can be seen that most species had a reduced distribution this year (even though 2006 had been a poor showing compared to 2005).

Trends over a longer period are presented separately at Annex B. Interestingly; four species have achieved wider distribution in the past five years than in the Millennium Survey. The Speckled Wood, continues its

Trans. Suffolk Nat. Soc. 44 (2008)

60

Suffolk Natural History, Vol. 44

progressive expansion, but rather surprisingly, White Admiral and White-letter Hairstreak are also shown as if expanding. This can be attributed to the determined recording effort that has pursued them.

Transects Distribution mapping does not assess a butterfly’s abundance at its breeding site as accurately as the “index” derived from transect walks. Generally, a fall in index figures will be detected prior to a diminishing distribution, and recent indices do reflect progressive falls in respect of Wall and Grayling. In absolute terms however, Small Heath numbers are holding up relatively well, with good showings at Cavenham Heath and the Devil’s Dyke. 16 full transects were walked this year, and the results were submitted promptly enough for the annual report of the UK Butterfly Monitoring Scheme. The scheme has collated data from 765 transects nationwide this year (the highest ever).

Special thanks are due to all our transect walkers for their commitment to regular monitoring at: North Warren (Rob Macklin), Fynn Valley (Richard Stewart), Minsmere (Robin Harvey), Bradfield Woods (Steve Hunt), Center Parcs (Graham Hersey-Green), Cavenham Heath (Michael Taylor), Walberswick (Will Russell), Spring Lane (Rob Parker), Combs Wood (Liz Cutting), Ramsey/Hintlesham & Wolves Wood (Mark Nowers), Newsons Farm (Frances Bee), Upper Abbey Farm (Trudy Seagon), Alton Water (Simon Waters), Manor Farm (Claire Studman), Tythe Farm (Peter Vincent), and Landguard (Dave Burgess). The Devil’s Dyke transect, (Sharon Hearle) mentioned above, lies on the county border and is technically outside Suffolk’s biological recording area.

Trans. Suffolk Nat. Soc. 44 (2008)

BUTTERFLY REPORT 2007

61

Annex A. Scarcity for 36 species seen in Suffolk in 2007 Tetrads per Species - 2006 & 2007 (Species listed in order of scarcity in 2007) % of 557 Tetrads tetrads 2006 Species 0·2 0·2 0·7

1 1 4

0·2 5·4 2·7 6·3 7·0 7·9 9·9 7·9 9·3 6·5 17·2 17·1 15·4 25·9 28·0 36·4 29·3 37·7 31·6 48·7 32·1 48·3 39·7 46·9 50·4 38·1 54·8 50·6 51·7 60·1 53·1 66·2

1 30 15 35 39 44 55 44 52 36 96 95 86 144 156 203 163 210 176 271 179 269 221 261 281 212 305 282 288 335 296 369

Purple Emperor Swallowtail Dingy Skipper Marbled White Large Tortoiseshell Camberwell Beauty Silver-studded Blue White-letter Hairstrk White Admiral Wall Clouded Yellow Purple Hairstreak Grayling Green Hairstreak Essex Skipper Small Heath Brown Argus Small Skipper Large Skipper Common Blue Small Copper Ringlet Brimstone Painted Lady Holly Blue Small Tortoiseshell Orange-tip Gatekeeper Comma Green-veined White Large White Peacock Speckled Wood Meadow Brown Small White Red Admiral

Tetrads % of 509 2007 tetrads *cf last Remarks 1 1 2 2 3 10 15 23 23 27 29 30 32 49 83 87 90 110 124 128 159 171 174 180 190 197 205 236 243 248 276 288 291 294 303 338

0·2 0·2 0·4 0·4 0·6 2·0 2·9 4·5 4·5 5·3 5·7 5·9 6·3 9·6 16·3 17·1 17·7 21·6 24·4 25·1 31·2 33·6 34·2 35·4 37·3 38·7 40·3 46·4 47·7 48·7 54·2 56·6 57·2 57·8 59·5 66·4

1·09 1·09 0·55 ~ 3·28 0·36 1·09 0·72 0·65 0·67 0·58 0·75 0·67 1·49 0·95 1·00 1·15 0·84 0·87 0·69 1·07 0·89 1·08 0·73 1·16 0·80 1·02 0·99 0·95 1·28 0·99 1·12 1·11 0·96 1·12 1·00

BAP sps in trouble Vagrants Survivors from 2006 But no.s well down A wet July A poor year Decline continues Few migrants A wet July Decline continues

A good year

Unexpectedly poor

Few migrants Cyclic recovery Another poor year

A good showing

Widespread again

36 species seen in Suffolk in 2007 (including introduced Purple Emperor) *cf “last” indicates the proportion of last years cover achieved in current year.

Trans. Suffolk Nat. Soc. 44 (2008)

62

Suffolk Natural History, Vol. 44

Annex B. ANALYSIS – 1995 to 2007 A measure of Abundance – for residents and regular visitors Survey from: to:

1995 1999

Period: Tetrads:Species/Tetrad:

5 yrs 1089 15·4

Small Skipper Essex Skipper Large Skipper Dingy Skipper Clouded Yellow Brimstone Large White Small White Green-veined White Orange Tip Green Hairstreak Purple Hairstreak White-letter Hairstreak Small Copper Silver-studded Blue Brown Argus Common Blue Holly Blue White Admiral Red Admiral Painted Lady Small Tortoiseshell Peacock Comma Speckled Wood Wall Grayling Gatekeeper Meadow Brown Ringlet Small Heath

639 714 639 5 147 473 920 953 973 858 151 216 40 543 17 320 635 703 56 809 570 982 923 619 452 350 182 937 1002 669 359

Notes: Rare migrants excluded

Trans. Suffolk Nat. Soc. 44 (2008)

2000 2004

2001 2005

2002 2006

5yrs 5yrs 5yrs 878 865 868 11·9 11·8 12·1 Tetrads from which recorded 261 290 322 240 253 267 228 259 295 7 7 8 192 87 111 249 290 317 579 617 599 576 622 606 520 572 552 401 455 439 83 85 88 109 112 120 43 54 70 297 310 341 20 20 20 160 169 193 327 367 383 370 476 419 36 46 61 538 571 577 410 396 448 538 615 621 468 527 532 403 457 475 535 572 565 200 183 163 107 107 107 495 524 504 582 615 591 334 378 397 195 205 209

2003 2007 5yrs 879 12·6 349 281 325 8 119 368 637 657 594 480 103 123 75 371 21 230 402 454 65 640 472 655 585 526 608 160 100 558 648 438 229

BUTTERFLY REPORT 2007

63

Annex B. ANALYSIS – continued

2003

Small Skipper Essex Skipper Large Skipper Dingy Skipper Clouded Yellow Brimstone Large White Small White Green-veined White Orange Tip Green Hairstreak Purple Hairstreak White-letter Hairstreak Small Copper Silver-studded Blue Brown Argus Common Blue Holly Blue White Admiral Red Admiral Painted Lady Small Tortoiseshell Peacock Comma Speckled Wood Wall Grayling Gatekeeper Meadow Brown Ringlet Small Heath

2004 2005 2006 2007

1yr 1yr 1yr 1yr 1yr 449 536 500 557 509 9·4 8·5 10 9·4 9·1 Tetrads from which recorded 114 121 135 158 110 88 102 107 100 83 90 90 121 161 124 5 7 4 4 2 40 36 13 55 29 100 106 163 176 174 251 283 316 305 276 245 293 317 296 303 203 257 302 212 248 151 199 244 221 205 29 31 43 36 49 40 37 46 44 30 25 13 22 35 23 141 160 144 163 159 18 11 17 15 15 82 65 53 86 90 156 164 188 203 128 82 185 281 179 190 17 13 32 39 23 288 225 285 369 338 275 143 95 271 180 289 332 334 269 197 219 231 302 282 288 221 198 267 281 243 245 270 307 288 291 83 66 39 44 27 52 34 38 52 32 194 248 249 261 236 235 291 294 335 294 150 161 179 210 171 93 93 94 95 87

Trend

Serious concern

Well recorded Stable

Expanding

Expanding Declining Declining

Declining

Trans. Suffolk Nat. Soc. 44 (2008)

64

Suffolk Natural History, Vol. 44

Annex C. Annual Report on Silver-studded Blue for 2007 Season The variable weather of 2007 led to the earliest-ever and the latest-ever sightings of Silver-studded blue. The early start was presumably due to the hot sunny April, and the first males were flying on 4 June. This disrupted our plans for the translocation to Blaxhall Common as well as the routine counts.

Rainy weather interrupted the progression of the emergence, as well as wrecking most of the pre-planned counts. At Wenhaston, the later flight period left at least one female flying on 2 September.

Positive Developments Despite the overall poor season, the Silver-studded blue’s extensions of range has continued. At Minsmere, some were seen in the reversion field adjacent to that colonised only last year. At Upper Hollesley, the flight area now extends inside the MoD boundary fence, and the nearby SCDC site is again occupied.

Lower Hollesley now extends to another two compartments (identified in the table below). The Parsnip Plantation colony, now in its fourth year, has also spread a few hundred metres.

Weak Colonies The three colonies about which concern was expressed in 2005 & 2006 are all still extant, with management work improving the habitat. At Wenhaston (Blackheath) the recently foraged area was in use by butterflies flying later than anywhere else. At Purdis Heath, the foraging has extended the pioneer heather area, though there were disappointingly few butterflies in the southern part of the heath. At Martlesham Heath, the new management plan has been put into effect, though the benefits are likely to be several seasons in the future yet.

Translocation to Blaxhall Common The planned translocation of butterflies to Blaxhall Common was undertaken early, with the collection of 30 from Minsmere Sawmills on 18 June. The overcast conditions made it easy to find them, but mating was not in progress, so 20 females and ten males were boxed and released at Blaxhall Common.

The second batch of 30 was taken from Lower Hollesley “A” on 3 July in brighter conditions, and included one mating pair. They apparently settled into their new habitat contentedly, and a field visit on 8 July found at least 14 flying in the release area. A transect walk has been set up, and volunteers will monitor success or failure in future seasons. A more detailed report of the translocation project has been published separately.

Survey Results The 2007 count was incomplete in two ways – poor weather at the main sites led to low counts, and the attempt was abandoned at 16 of the smaller Minsmere compartments. Thus, the results are not a proper assessment of the butterflies on the wing this year. The resulting total figure of 1525 compares very badly (just 28%) with last year’s high count of 5470. At individual sites, that comparison varied between 20% (Aldringham Walks) and 86%

Trans. Suffolk Nat. Soc. 44 (2008)

BUTTERFLY REPORT 2007

65

(Walberswick). It seems fair to judge that the extended flight period across a showery summer resulted in the poor showing, and that this should not be taken as an overall population crash.

The mini transects at Minsmere suggest that the male population was approaching a peak on 19 June, with females beginning to increase just as the wet weather arrived. By 4 July, two days after the attempted count, the sex ratio was falling through 2:1. By these measures then, the timing of the count was not far off, but the peak was presumably lowered by the extended flight period as well as the lack of sun.

The distribution map for the 2007 counts shows records from 14 tetrads, and is reproduced below. This appears to match last year’s tetrad cover, but the omission of one Minsmere tetrad is offset by the addition of Blaxhall Common (TM377566). Such a map shows presence, but does not reveal the condition of each site or its butterfly colony. In general, the larger, well-managed coastal sites are doing well, whilst the isolated inland sites are those where the colony has a weaker tenure.

2007 Count Map: 15 tetrads

Trans. Suffolk Nat. Soc. 44 (2008)

Suffolk Natural History, Vol. 44

66

Monitoring The results of the 2007 counts are summarised below. Only 23 of the 44 listed locations were successfully surveyed, sites not counted are marked *.

2007 COUNTS – Monitored Silver-studded Blue Sites listed geographically from the North Location Blackheath Wenhaston Walberswick Comn NNR Aldringham Walks Westleton Heath NNR Westleton Common Westleton Football Pitch Minsmere Foraged Square Minsmere Reversion Field Minsmere Sawmills Minsmere Football pitch Minsmere Natterjack pond Minsmere SW Comp 1 Minsmere Pit Comp2 Minsmere SE Comp 3 Minsmere Comp 20 N Minsmere Comp 20 S Minsmere S Comp3 Minsmere Central Comp 3 Minsmere Powerlines Minsmere North Bridleway Minsmere Potbriggs Minsmere North Grimstones Minsmere E Comp 13 Dunwich Heath Minsmere Gravel Pit Blaxhall Common UHC 3d Upper Hollesley MOD SCDC Lower Hollesley ‘A’ Lower Hollesley ‘B’ Lower Hollesley ‘C’ LHC Barthorpes small Firebreak LHC compt 8c Rushmere Heath Martlesham Heath Parsnip Plantation Ipswich Golf Club, Purdis Purdis Heath Industrial Estate Ind. Est. lagoon fringe

Grid Ref.

Date

TM420749 TM491752 TM464612 TM4569 TM44306870 TM44406880 TM459689 TM451689 TM452692 TM451691 TM451693 TM450694 TM457692 TM457691 TM446683 TM445680 TM456693 TM453693 TM461683 TM468687 TM468689 TM462688 TM468681 TM468687 TM449669 TM377566 TM3376024800 TM33344723 TM3357447121 TM342465 TM343461 TM352458 TM3495346020 TM350456 TM3382846820 TM202448 TM2344 & 2444 TM32724579 TM207415 TM21204270 TM207419 TM207415

06.08 06.07 08.07 06.07 19.06 19.06

Trans. Suffolk Nat. Soc. 44 (2008)

02.07 02.07

02.07 02.07

03.07 22.06 05.07 05.07 27.06 05.07 25.06 25.06 25.06 15.06 ~ 08.07 27.06 ~ 01.07

Observer Richard Havard Adam Burrows Rob Macklin Adam Burrows David Rous David Rous

♂ 13 21 20 108 113 5

♀ Total

13 11 32 12 32 22 130 18 131 1 6 * Rob Parker 0 Mel Kemp 114 117 231 * * * * * * * * * * * Mel Kemp 38 9 47 Mel Kemp 191 147 338 * 0 * Terry Peake 11 20 31 David Mason 1 1 David Mason 40 11 51 David Mason 5 2 7 David Mason 112 19 131 Richard Stewart 54 9 63 David Mason 24 2 26 David Mason 12 4 16 David Mason 3 2 5 David Mason 5 5 not checked 0 Phil Smith not split 160 David Mason 12 3 15 Neil Sherman 0 0 0 Neil Sherman 12 3 15 Julian Dowding not split 40 0 2007 Totals: 913 413 1525

BUTTERFLY REPORT 2007

67

A year-on-year comparison for the main sites shows how poor this year’s results are: YEAR on YEAR Totals for main sites Location

Grid Ref.

Blackheath Wenhaston Walberswick Comn NNR Aldringham Walks Westleton Heath NNR Westleton Common Minsmere Sawmills Minsmere Potbriggs Minsmere North Grimstones Upper Hollesley MOD Lower Hollesley ‘A’ Lower Hollesley ‘B’ Lower Hollesley ‘C’ Martlesham Heath Purdis Heath Industrial Estate

TM420749 TM491752 TM464612 TM4569 TM44306870 TM452692 TM468689 TM462688 TM33344723 TM342465 TM343461 TM352458 TM2344 & 2444 TM21204270 TM207419

2004 2005 2006 2007 3 44 266 135 290 962 210 1188 167 608 342 ~ 259 63 101

1 24 36 37 217 154 176 164 252 365 ~ 1094 47 148 405 757 192 76 467 271 335 234 24 55 377 280 6 25 67 127

13 32 32 130 131 231 47 338 51 131 63 26 159 15 71

Some of the results are shown graphically below. The abrupt decline at Aldringham Walks gives cause for particular concern.

Annual SSB Counts 350 300 250 Aldringham

200

Walberswick

150

Blackheath

100 50 0 2004

2005

2006

2007

Trans. Suffolk Nat. Soc. 44 (2008)

68

Suffolk Natural History, Vol. 44

Annex D. Dingy Skipper Survey, 2007 SUMMARY Spring 2007 came early. April was extremely hot and dry, leading to early emergences for most spring species, including the Dingy Skipper, which was on the wing in Cambridgeshire by 24 April. It may also have flown in Suffolk in the last days of April, but remained unobserved until the last day of the hot spell, with one sighting at Wordwell on 6 May. Cool, wet weather then reigned for ten days, and the next Suffolk sighting was of four in the sheltered belt to the north of the Archery area on 18 May. A frustrating period followed, with plenty of survey activity for very few sightings. In all probability, an early flight period had been missed, and in subsequent weeks only small numbers of late-emerging butterflies were seen.

All visits were conducted with the landowner’s consent, or along public rights of way. A total of seven sites were visited during the 2007 flight period.

Priority was given to RAF Barnham, which was visited three times during the flight period, but without a single sighting. Dingy Skippers were found only at the established sites in the King’s Forest. A single visit to the isolated colony at Center Parcs did not find any on 24 May, although a worn singleton was still flying in the King’s Forest (Wordwell) on 3 July. The butterfly is losing ground rapidly, even within its core area in King’s Forest. This year, it was found in only two tetrads. Regrettably, the real cause of the decline is not properly understood. The only scope for optimism lies in the belief that an unobserved early flight period may have laid eggs before the weather deteriorated.

The sites visited are listed individually below, with more detail.

SURVIVING COLONIES King’s Forest (Wordwell) [TL834732] – This site recorded a maximum count of six on 18 May, and again the Dingy Skippers were flying further to the south and west than the main ride. The plantation to the north west of this area was clear felled last year, partially opening a route between the Wordwell ride and the Archery site, but this seems unlikely to become hospitable to Dingy Skippers before the newly planted conifers shade it out.

King’s Forest (Archery) [TL831737] – The area used for archery practice, part of which is mown, had Dingy Skippers on 18 May. On 19 May, a party of nine volunteers searched in overcast conditions, but saw none. At least four were present on 23 May in better weather, however. Compared with 2005’s exceptional count of 107, this is very disappointing, but at least the colony survives. The bird’s-foot trefoil was late to flower, and there was very little nectar available for butterflies even in the last week of May. King’s Forest (Chalk Lane) [TL827752] – Two Dingy Skippers were found in the Chalk Lane area on 24 May, but not by a number of other searches, mainly in imperfect weather conditions.

Trans. Suffolk Nat. Soc. 44 (2008)

BUTTERFLY REPORT 2007

69

OTHER SITES (NONE FOUND) Elveden (Center Parcs) [TL810805] – One organized search on 24 May proved fruitless, and there were no casual sightings by the Center Parcs staff.

The area mown as the bird walk is managed with the Bird’s-foot trefoil in mind, and the drainage ditch has been cleared of self-seeded trees, which has created some reasonable looking habitat.

RAF Barnham [TL8580/8680] – Three visits were made to the Barnham Training Area, but not a single Dingy Skipper was seen. The first check was a thorough search of the normal flight area, made on a cool overcast 19 May. Although no Dingy Skippers were seen, a habitat condition survey was completed, and showed that although the former best area has been largely shaded out, there remains a sizeable area of apparently suitable habitat. The bird’s-foot trefoil was growing again after last year’s grazing, but was barely in flower. Sheep-grazing had not resumed for 2007 by 24 May, when another negative search was made. Two tiny larvae were found on the bird’s-foot trefoil, but they were too small for identification, and were probably a moth species.

Thetford Rifle Range [TL8480] – This MoD site lies in Administrative Norfolk, but is in Suffolk’s biological recording area. It has plenty of Bird’sfoot trefoil in a suitably sheltered area, and was walked extensively in 2005.

Although the habitat looked excellent again this year (after firing 24 May), it was disappointing not to find any Dingy Skippers.

Marmansgrave Wood [TL8480] – Another negative search along the footpath (24 May 07) confirmed the view that this former site may be considered defunct.

OTHER SITES (for future searches, but not checked in 2007) Barnhamcross Common [TL864811] – This site lies adjacent to RAF Barnham, and occasional strays have been seen on the south edge of Barnhamcross Common, which lies in administrative Norfolk, but in Suffolk’s biological recording area. Two visits were made to the southern margin in 2006, but no Dingy Skippers were found. This is hardly surprising, given the absence of activity on RAF Barnham.

Kings Forest South [TL7872/8073/8272SW] – None noted here for a decade, but worth an occasional check.

King’s Forest (John O’Groats Cottages) [TL818737] – This area, and the sector to the north of it, contains a number of isolated patches of bird’s-foot trefoil growing in sheltered rides. Two unexpected 2005 sightings in the TL818758 vicinity give hope that they may have re-colonized. This area is a priority for further survey work in 2008.

Sketchfar [TL836801] – The sheep-grazed area in the Elveden Estate’s Sketchfar domain has one promising looking corner, which deserves a visit next year. It lies close to the defunct site at Marmansgrave Wood.

Trans. Suffolk Nat. Soc. 44 (2008)

70

Suffolk Natural History, Vol. 44

Euston Quarry [TL896775] – This wonderful CWS has everything that ought to make a good Dingy Skipper site, including Bird’s-foot trefoil and a Common Blue colony. It was not checked this year.

Cut-off Channel [TL7386] – During Norfolk’s 2004 survey for Grizzled and Dingy Skipper, both were found along the watercourse known as the Cut-off channel, which has a chalky double embankment along a nine mile stretch in Norfolk. Visits to the Suffolk stretch were made on 12 May (after finding DS flying in nearby Norfolk), but there was a shortage of Bird’s-foot trefoil, and nothing was seen.

Annex E. White-letter Hairstreak – 2007 The White-letter hairstreak has now been accepted as a UK BAP species, and its future is viewed with some concern largely because of the uncertain consequences of Dutch Elm disease.

In Suffolk, we have been working so hard to unearth surviving colonies of this previously under-recorded insect that, distribution figures appear to show a substantial increase. Analysis shows that the number of tetrads occupied by White-letter hairstreak has increased from 40 to 109 since the Millennium survey, but this apparent spread must be treated with caution. On the one hand, the butterflies are showing some adaptability in leaving elms infected by the disease, and they are moving on to younger suckers elsewhere. This adaptability could be an effective survival mechanism, but it also leaves dots on distribution maps at sites not permanently colonised, and is thus misleading. Our volunteer recorders are also becoming more skilled at finding small colonies at the same time as the butterflies are becoming easier to find due to lower elm canopies. This year, a succession of hot summers came to an end, with a cool, wet July, and finding them was not easy.

That said, the White-letter hairstreak was recorded from 4·5% of squares surveyed (23 tetrads) in 2007, including observations from seven fresh squares. This brings the total to 109 tetrads in which it has been found at some time in the last 13 years (a remarkable 10% of all tetrads). It is clear that the butterfly is surviving at many small sites spread across the county, many of them no more than a stretch of roadside elm hedge. Future monitoring will include continued participation in a nationwide initiative, which is reported at: http://www.w-album.hertsmiddx-butterflies.org.uk/ Rob Parker 66 Cornfield Road Bury St Edmunds Suffolk IP33 3BN

Trans. Suffolk Nat. Soc. 44 (2008)