Suffolk Natural History, Vol. 46

48

2009 BUTTERFLY REPORT ROB PARKER After two poor years, 2009 came as something of a relief. For most species, it has been a decent season, and the major immigration of Painted Lady was very welcome. Only for a few species has it been a poor year, and long-term declines account for some of these. Good recording effort has resulted in meaningful coverage for the whole of the 5-year period. Annexes A and B provide analysis of the season’s results and compare them with previous years. Weather The winter was colder than recent mild years, and even below average judged by historic averages, with February bringing frosts, cold winds and snow. In all, air frosts occurred 38 times in East Anglia. Thereafter, things improved, and 15 March was warm enough to bring out first butterfly sightings for many observers. Spring was warmer, sunnier and drier than 2008. The summer figures in the table below are averages, and mask the reality that July was very wet (15 rainy days), whereas August and September were unusually dry, creating conditions of drought for some larval host plants. Table 1. 2009 Weather for East Anglia Season Winter 08/09 Spring Summer Autumn

Mean Temp

Anomaly Sunshine Anomaly Rainfall

Anomaly

Deg °C

Deg °C

hrs

%

mm

%

3·5 10·0 16·8 12·0

-0·8 1·4 0·8 1·4

179 547 622 348

103 121 107 107

134 85 154 162

91 63 103 94

Source: www.metoffice.gov.uk/climate/uk Anomalies are measured against the 1971 to 2000 averages [updated baseline]. The shortage of sunny April days with temperatures of above 16 °C (at the SNS weather station in Boxford) again explains why transect walkers had difficulty in getting any walks in within the stipulated weather criteria. May was slightly better, but there were still twelve days that failed to meet the basic butterfly flight criteria, delaying the emergence of species that had passed the winter as pupae. In June there were 13 days that provided little opportunity for flight, or pairing. The frost and snow of December (the coldest December for 15 years) will be bad news for some species, particularly overwintering Red Admirals. However it could also kill parasitic fly and wasp species, once again bringing benefits for host species next year.

Trans. Suffolk Nat. Soc. 46 (2010)

NOTES BUTTERFLY ON SOME SUFFOLK REPORTMOTHS 2009 2009

49

Monitoring the BAP Species There are now five Suffolk BAP priority species, and two in a new category of “for study only”. The annual Silver-studded Blue count missed the peak at several of the major sites, but numbers were generally close to 2006 levels. A professional ecological survey was conducted by Neil Ravenscroft, and provided useful data for conservation at our most threatened sites. The translocated colony at Blaxhall Common survived another season, and up to 21 butterflies were recorded on the transect, flying over a five week period. See Annex C for more detail. For the fourth year in succession, the Dingy Skipper was not found at RAF. Barnham, and the colony has probably been lost. Again, there were no sightings from the small isolated site at Center Parcs, and this too may have been lost. In the King’s Forest, the habitat is in transition, with decent numbers breeding only at the archery site, so the overall picture is gloomy. See Annex D for more detail. White-letter Hairstreak was one of the species that was hard to find in 2009, partly because of July’s wet weather. In the period 2005 to date, it has been found in almost 8% of the county’s 1088 tetrads, but it was seen in only 2·5% of the tetrads surveyed in 2009. See Annex E for more detail. White Admiral continues to do well in Suffolk woodlands. This year, it was noted in 26 tetrads (4%) compared with 13 (1%) in the whole of the 1983–1985 survey. The situation here is more favourable than in the UK as a whole. See Annex F for more detail. Grayling is in general decline across Suffolk, but enjoyed a good season at several coastal sites, particularly at North Warren. Its present distribution is restricted to well-drained sandy soils of low fertility, where sparse grassland is found, mainly in the Brecks and the Sandlings. See Annex G for more detail. The UK BAP species list includes two further species for enhanced monitoring. In both cases, the larval host plant is grass: Wall is in decline in the UK and in Suffolk. Lost from inland locations, its distribution is now restricted to well-drained sandy soils of low fertility, particularly down the east coast, with a lesser stronghold in the NW corner of the county. In 2009, it was found in 5·6% of the surveyed tetrads, against 12% over the past five years. Small Heath is in a less critical situation than the Wall, but is losing ground on farmland amongst fertilized grass. It has been recorded from 234 tetrads in the past five years (24% of 994 recorded tetrads), but numerical counts are falling at the few transect sites which still support it.

Residents – Winners and Losers Some of our resident species had an encouragingly good season. In particular, the Small Tortoiseshell made quite a come-back, being the season’s first sighting for many recorders, along with Peacocks, Commas and Brimstones, mainly during a bright spell in mid March. Partly this was due to an immigration of healthy Small Tortoiseshells over-wintering successfully after their arrival in late Aug 2008, probably enhanced by reduced parasitism from

Trans. Suffolk Nat. Soc. 46 (2010)

50

Suffolk Natural History, Vol. 46

the Tachinid fly Sturmia bella, which suffered losses during the colder winter. The good showing of Vanessids and Whites in gardens, along with immigrants, left an impression of abundance that was not valid for all species. The Common Blue and Brown Argus, both recovered after poor seasons in 2007/2008. Small Copper numbers were average, whilst Holly Blue appeared to have begun one of its periodic downturns, with a poor showing in the second generation. Small and Essex Skippers maintained their distribution but were not particularly abundant, whereas the Large Skipper had a better than average year. The commoner Browns all had a good year, particularly the Speckled Wood. The less mild winters have checked the surge of the Red Admiral somewhat, but it was present everywhere, and was still flying into December, albeit in small numbers. Purple Emperor The introduced Purple Emperors were still flying, not only in Theberton Woods, but also putting in an appearance at Minsmere. A male was photographed from the RSPB’s canopy hide on 19 July and was much observed until 23 July. Perhaps this heralds a spread to the wider area of sallow lined ditches between the two sites. One possible female sighting at Minsmere was not confirmed by photography. A separate Purple Emperor sheltering from the rain in Bury St Edmunds is more difficult to explain. Migrants 2009 was an interesting year for migrants and other unusual observations. A few isolated Painted Lady sightings in mid May were overtaken on 23/24/25 May by a major immigration, first evident along Suffolk’s east coast, but occurring simultaneously along the entire south coast of England too. Classic streams of migrants flying determinedly northwest at shoulder height were counted at over 100 per hour in many hotspots, particularly along our river valleys. The butterflies were worn and faded, and climbed up over trees or houses, before descending again, and continuing without pausing for nectar. The event was monitored and recorded in real time, on-line by Butterfly Conservation’s Migration Watch. During that influx, there were very few mentions of other butterfly species, but Hummingbird Hawk Moths arrived too, and later in the season small numbers of Clouded Yellows. In the days following the main Painted Lady influx, it appeared that most had flown beyond Suffolk, but some paused for nectar and egg-laying on thistle. The Clouded Yellows mostly paused to lay eggs on coastal clover patches. The resultant generations put Painted Lady in most Suffolk gardens in July, and selected coastal locations had Clouded Yellows in clusters in September. Both species continued to fly right through October and into a mild November. By the end of the season, Painted Lady had been recorded from 69% of tetrads visited. Vagrants and Unusual Sightings July brought three separate sightings of Marbled White. One singleton was seen near the Cambs border at Kirtling, another in the Fynn Valley, and the third in the King’s Forest; all were flying in suitable looking grassland habitat

Trans. Suffolk Nat. Soc. 46 (2010)

NOTES BUTTERFLY ON SOME SUFFOLK REPORTMOTHS 2009 2009

51

and identified by reputable observers. Marbled White was also present on the Cambridgeshire border on the Devil’s Dyke, and it is possible that climate change is extending its range. At least three Silver-washed Fritillary were unexpectedly seen in a private wood near Stowmarket in July. An optimistic explanation might be to hope that they arrived with the Silver-washed expansion in 2006, and have been breeding ever since. No such interpretation can be put on the two Tiger Swallowtails from North America (Papilio rutulus) that turned up in Long Melford and Sudbury in September. These were in local gardens, and must have been releases. An unexpected female Long-tailed Blue probably arrived as a stowaway in imported peas. Early and Late Records Following a cooler, more “normal” winter, spring 2009 did not bring any earliest-ever records. Thereafter the season was of a stop-go nature, with alternating drought and heavy rain, followed by a mild autumn and a particularly gentle November – but still without any latest-ever records. Geographic Coverage As the final year of the five-year period, 2009 brought a challenge to extend cover from 80% by filling the unvisited “black holes”, and many recorders rose to the challenge. A record total of 645 tetrads were visited, bringing overall cover up to 91% of the county during the 5-year period. This honourable achievement looks perfect when measured at the 10km square scale required for the national records. The area covered most thinly is the agricultural land in High Suffolk, where both the human population and the butterfly density are inherently low. Improving cover in this area sets a challenge for the future, as there must be some pockets of decent habitat that remain undiscovered. 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 34, including the introduced Purple Emperor, but excluding the Long-tailed Blue and the Tiger Swallowtails. The average number of species recorded per tetrad was 10·3, the highest annual figure since the start of the Millennium survey. Analysis The 34 species that put in an appearance this year are shown in Annex A, in order of scarcity, with a direct comparison to last year’s turnout. Our most widespread residents were reshuffled this year, with Meadow Brown losing its place to the migrant Painted Lady and Large White. Small White, Speckled Wood and Peacock remain ahead of Small Tortoiseshell, despite its partial recovery. Red Admiral has fallen back to eleven from its lead position of two years ago. Brown Argus and Common Blue both made convincing recoveries from their poor performance last year. The change in distribution from last year to this is expressed in the “c.f. last” column, and it can be seen that most species improved this year, spectacularly in the case of the migrant Clouded Yellow and Painted Lady. Holly Blue and White-letter Hairstreak, on the other hand, have both been seen in far fewer tetrads than in 2008.

Trans. Suffolk Nat. Soc. 46 (2010)

52

Suffolk Natural History, Vol. 46

Trends over a longer period are presented separately at Annex B for our 31 regulars. Species that have achieved wider distribution in the past five years than in the Millennium Survey continue to hold their positions. In particular, the Speckled Wood continues its progressive expansion. White Admiral and White-letter Hairstreak are again shown as expanding, although this is partly due to the determined recording effort that has pursued them. The decline of the Dingy Skipper is masked because of an expansion into two extra tetrads of the King’s Forest. Transects Any analysis derived from distribution maps and counts of presence/absence responds rather slowly to changes in a species’ health. The “index” derived from transect walks, on the other hand, gives a valid evaluation of a species’ abundance in the current year, providing a more sensitive indicator of change, albeit at specific sites. The 16 full transects walked this year confirmed a slight improvement for Brown Argus, but a long-term decline of several other species including Common Blue, Small Heath and Grayling (only found at a few sites). 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 and Wolves Wood (Mark Nowers), Newsons Farm (Frances Bee), Upper Abbey Farm (Trudy Seagon), Alton Water (Simon Waters), Manor Farm (Brenda Hudson) and Tythe Farm (Peter Vincent). Single-species transects for Purple Hairstreak (Steve Hunt) and Silver-studded Blue (Terry Peake) also produced useful results. In almost every case, additional volunteers (not named individually) assisted the lead walker.

Trans. Suffolk Nat. Soc. 46 (2010)

NOTES BUTTERFLY ON SOME SUFFOLK REPORTMOTHS 2009 2009

53

Annex A. Scarcity for 34 species seen in Suffolk in 2009 Tetrads per Species - 2008 & 2009 (Species listed in order of scarcity in 2009) % of 549 Tetrads tetrads 2008 0·4 0·4 0·4 0·2 0·4 4·4 2·7 5·8 5·1 6·4 6·7 6·0 0·9 15·3 18·0 6·9 35·9 22·8 26·4 23·9 28·6 43·0 23·3 44·8 52·6 54·6 51·2 55·9 43·9 55·9 57·7 55·6 65·8 12·4 62·5

2 2 2 nil 1 nil 2 24 15 32 28 35 37 33 5 84 99 38 197 125 145 131 157 236 128 246 289 300 281 307 241 307 317 305 361 68 343

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

Tetrads % of 645 2009 tetrads *cf last Remarks nil nil nil 1 2 3 5 16 17 26 36 41 54 56 57 100 106 128 153 169 188 199 199 244 249 268 283 351 354 392 398 408 411 425 434 447 469

0·2 0·3 0·5 0·8 2·5 2·6 4·0 5·6 6·4 8·4 8·7 8·8 15·5 16·4 19·8 23·7 26·2 29·1 30·9 30·9 37·8 38·6 41·6 43·9 54·4 54·9 60·8 61·7 63·3 63·7 65·9 67·3 69·3 72·7

1·70 2·13 0·57 0·96 0·69 1·09 1·00 1·24 1·44 9·70 1·01 0·91 2·87 0·66 1·15 1·10 1·29 1·08 0·88 1·66 0·93 0·83 1·00 1·07 1·09 1·41 1·13 1·10 1·19 1·02 5·60 1·16

All 5 tetrads in KF*

Good migration yr.

Periodic trough

Strong migration

34 species seen in Suffolk in 2009 (including introduced Purple Emperor) *cf “last” indicates the proportion of last years cover achieved in current year. “cf last” can be misleading for species seen in less than 20 tetrads due to variable coverage from year to year. *KF = The King’s Forest

Trans. Suffolk Nat. Soc. 46 (2010)

54

Suffolk Natural History, Vol. 46

Annex B. ANALYSIS - 2001 to 2009 Long term trends - for residents and regular visitors (as at 22 Jan 2010).

Survey from: to: Period: Tetrads:Species/Tetrad:

2001 2002 2003 2005 2006 2007 5yrs 5yrs 5yrs 865 868 879 11·8 12·1 12·6 Tetrads from which recorded Small Skipper 290 322 349 Essex Skipper 253 267 281 Large Skipper 259 295 325 Dingy Skipper 7 8 8 Clouded Yellow 87 111 119 Brimstone 290 317 368 Large White 617 599 637 Small White 622 606 657 Green-veined White 572 552 594 Orange Tip 455 439 480 Green Hairstreak 85 88 103 Purple Hairstreak 112 120 123 White-letter Hairstreak 54 70 75 Small Copper 310 341 371 Silver-studded Blue 20 20 21 Brown Argus 169 193 230 Common Blue 367 383 402 Holly Blue 476 419 454 White Admiral 46 61 65 Red Admiral 571 577 640 Painted Lady 396 448 472 Small Tortoiseshell 615 621 655 Peacock 527 532 585 Comma 457 475 526 Speckled Wood 572 565 608 Wall 183 163 160 Grayling 107 107 100 Gatekeeper 524 504 558 Meadow Brown 615 591 648 Ringlet 378 397 438 Small Heath 205 209 229

2004 2008 5yrs 918 12·7 362 296 347 8 104 394 683 685 632 522 108 116 81 369 21 215 404 502 68 655 403 644 621 557 636 136 95 593 699 473 236

2005 2009 5yrs 994 13·1 390 296 412 8 118 442 785 775 718 552 113 128 79 376 22 260 475 504 71 699 604 698 700 635 724 120 104 663 789 528 234

Notes: Only one colony of Dingy Skipper was found in 2009, but this extended over 5 tetrads, which masks the seriousness of its decline. Rarities excluded.

Trans. Suffolk Nat. Soc. 46 (2010)

NOTES BUTTERFLY ON SOME SUFFOLK REPORTMOTHS 2009 2009

55

Annex B. ANALYSIS – continued

2005 2006 2007 2008 2009 Trend 1yr 1yr 1yr 1yr 1yr 500 557 509 549 645 10 9·4 9·1 9 10·3 Tetrads from which recorded Small Skipper 135 158 110 125 169 Essex Skipper 107 100 83 99 106 Large Skipper 121 161 124 131 199 Dingy Skipper 4 4 2 2 5 Serious concern Clouded Yellow 13 55 29 5 57 Migrant; variable Brimstone 163 176 174 157 199 Large White 316 305 276 343 469 Small White 317 296 303 305 425 G-veined White 302 212 248 307 392 Orange Tip 244 221 205 236 244 Green Hairstreak 43 36 49 35 41 Purple Hairstreak 46 44 30 33 56 W-letter Hairstreak 22 35 23 24 16 2009 poor season Small Copper 144 163 159 145 188 S-studded Blue 17 15 15 15 17 Stable Brown Argus 53 86 90 38 128 Decline checked Common Blue 188 203 128 128 249 2009 a good year Holly Blue 281 179 190 197 153 White Admiral 32 39 23 32 26 Expanding Red Admiral 285 369 338 289 283 Painted Lady 95 271 180 68 447 Major influx 2009 Sm Tortoiseshell 334 269 197 241 398 Peacock 302 282 288 307 408 Comma 267 281 243 300 351 Speckled Wood 307 288 291 317 411 Still expanding Wall 39 44 27 28 36 Long-term decline Grayling 38 52 32 37 54 Gatekeeper 249 261 236 281 354 Meadow Brown 294 335 294 361 434 Ringlet 179 210 171 246 268 Small Heath 94 95 87 84 100 Decline checked Period: Tetrads:Species/Tetrad:

% of County (1089 tetrads) 20052009 36 27 38 1 11 41 72 71 66 51 10 12 7 35 2 24 44 46 7 64 55 64 64 58 66 11 10 61 72 48 21

Trans. Suffolk Nat. Soc. 46 (2010)

56

Suffolk Natural History, Vol. 46

Annex C. Annual Report on Silver-studded Blue for 2009 Season The first records of 2009 were of larvae – a reminder that we have not routinely searched for early stages.The first males were flying by 2 June (13 days earlier than 2008). Peak counts at most sites were achieved during the last week of June and by the first week of July had passed their peak. As usual, the latest sightings occurred at Blackheath (on 24 Aug), although some were still flying at Lower Hollesley on 22 Aug. Accidental Fires Accidental fires occurred at Martlesham heath, Blackheath and Aldringham Walks. In each case, no serious damage was done to heathland habitat, and the fires will probably create improved patches of pioneer heather habitat in two to three years. Positive Developments Further consolidation in Minsmere’s reversion field brought a new high count of 864. Blaxhall Common The transect walk at Blaxhall Common found about a dozen Silver-studded Blues on the wing over a 5 week period from 29 June to 26 July.This is a very satisfactory consolidation for the second full year of monitoring the translocated colony. Results of Annual Count All the main sites were counted, albeit somewhat after the peak in some cases, and a number of the small sites were missed this year as a consequence. A total of only 33 of 47 sites were counted, but the resulting total figure of 4324 was higher than 2008, and compares reasonably (at 79%) with 2006’s high count of 5470. Most sites can thus be considered to be in good health, leaving three where there is longstanding cause for concern. In addition, heather encroachment at Minsmere Potbriggs has seriously degraded the site, and will need to be tackled if the colony is to be re-instated. Ecological Survey of Selected Weak Colonies The three colonies about which concern has been expressed since 2005 were the subject of a specially commissioned ecological survey by Neil Ravenscroft. His report (downloadable from www.suffolkbutterflies.org.uk) provides useful guidance on future habitat management at Purdis Heath, Martlesham Heath and Blackheath. The progressive deterioration of habitat at Purdis Heath has left a particularly worrying situation, with a count of just 21. Tabulations The results of the 2009 counts are tabulated below. Of the 33 colonies successfully surveyed, just three were unoccupied. Excluding a probable release noted in Holywells Park (Ipswich), 16 tetrads (the usual number for recent years) were occupied. A year-on-year comparison for the main sites (second table) reflects a slightly better year than 2008 overall, but reveals downward fluctuations at some sites:

Trans. Suffolk Nat. Soc. 46 (2010)

NOTES BUTTERFLY ON SOME SUFFOLK REPORTMOTHS 2009 2009

57

2009 COUNTS Location

Grid Ref.

Date

Observer

♂

Blackheath Walberswick Com Walberswick NNR Westleton Heath Westleton Com Westleton Football Mins Foraged Square Mins Reversion Fld Mins Sawmills Mins Football Mins Natterjack pit Mins SW Comp 1 Mins Pit Comp2 Mins SE Comp 3 Mins Comp 20 N Mins Comp 20 S Mins S Comp3 Mins Cent Comp 3 Mins Powerlines Mins N Bridleway Mins Potbriggs Mins N Grimstones Minse E Comp 13 Mins Comp 13 track Mins Tanktrap

TM420749 TM491752 TM451727 TM4569 TM443687 TM444688 TM459689 TM451689 TM452692 TM451691 TM451693 TM450694 TM457692 TM457691 TM446683 TM445680 TM456693 TM453693 TM461683 TM468687 TM468689 TM462688 TM468681 TM464681 TM466683

26.07 01.07 01.07 01.07 26.07 26.07

R Havard B Andrews B Andrews B Andrews D Rous D Rous M Kemp M Kemp M Kemp M Kemp M Kemp M Kemp M Kemp M Kemp M Kemp M Kemp M Kemp M Kemp M Kemp M Kemp M Kemp M Kemp M Kemp M Kemp M Kemp

30 7 22 82 242 6

32 1 9 27 57 2

565 224 117 12 3 58 6 15

299 159 81 9 1 83 10 23

864 383 198 21 4 141 16 38

220

267

487

Dunwich Heath Minsmere Gravel Pit

TM468687 TM449669

06/07 08.07 M Kemp

0 1

0 1

0 2

Aldringham Walks Blaxhall Common UHC 3d Upper Hollesley MOD SCDC Lower Hollesley 'A' Lower Hollesley 'B' Lower Hollesley 'C' LHC Barthorpes LHC compt 1e Firebreak LHC compt 8c

TM464612 TM377566 TM337480 TM333472 TM335471 TM342465 TM343461 TM350458 TM349460 TM346462 TM350456 TM338468

24.06 25.06 29.06 30.06 30.06 30.06 30.06 24.06 24.06 24.06 25.06 24.06

48 15 0 111 6 185 268 99 25 6 7 44

10 4 0 30 0 46 62 10 1 0 1 11

01.07 01.07 01.07 08.07 08.07 08.07 08.07

01.07

R Macklin D Mason D Mason D Mason D Mason R Stewart R Stewart D Mason D Mason D Mason B Calvesbert D Mason

♀

Total Comment 62 Late colony 8 31 109 299 8 No Count Past peak Past peak Past peak Past peak Past peak Past peak Past peak Past peak No count No count No count No count No count Bracken Past peak No count No count No count None since 2005 Past peak Low count, fire

58 19 0 141 late colony 6 231 85% of 2006 330 109 26 6 8 55

continued over page

Trans. Suffolk Nat. Soc. 46 (2010)

Suffolk Natural History, Vol. 46

58

2009 COUNTS Continued Date Observer

♂

♀

Location

Grid Ref.

Rushmere Heath

TM202448

Martlesham Heath

TM2344 & 2444 27.06 P Smith

290

184

Parsnip Plantation

TM327458 30.06 D Mason

46

25

Ipswich Golf Club

TM208432

N Sherman

0

0

0

Purdis Heath

TM212427 28.06 N Sherman

16

5

21

Industrial Estate

TM207419 24.06 J Dowding

67

31

98

Ind. Est. Jacobsen

TM200410

J Dowding

No count

Ind. Est. lagoon fringe TM207415

J Dowding

No count

2009 Totals:

2843 1481 4324 2006 Totals: 3617 1438 5470

Good year:

Total Comment

~

No count Fire

This year:as % of 2006

474 6/5/09 71

79%

YEAR on YEAR Totals for main sites Location Blackheath Walberswick NNR Westleton Heath Westleton Com. Mins. Sawmills Mins. Potbriggs N. Grimstones Aldringham Walks Blaxhall Common Up. Hollesley MoD Lower Hollesley 'A' Lower Hollesley 'B' Lower Hollesley 'C' Martlesham Heath Purdis Heath Industrial Estate Total

2004 2005 2006 2007 2008 2009 3 44 135 290 962 210 1188 266 167 608 342 259 63 101 4638

1 36 176 252

24 37 164 365 1094 47 148 405 757 217 154 192 76 467 271 335 234 24 55 377 280 6 25 67 127 2602 3811

Trans. Suffolk Nat. Soc. 46 (2010)

13 8 62 32 22 31 130 75 109 131 335 299 231 563 383 47 60 0 bracken 338 600 487 32 67 58 60 15 19 51 176 141 131 176 231 63 283 330 26 66 109 159 126 474 15 16 24 concern 71 66 98 1530 2654 2855 Overall:

2009/2006 2·58 0·84 0·66 0·82 0·35 0·00 0·64 0·38 n/a 1·86 0·85 1·41 1·98 1·69 0·96 0·77 0·75

NOTES BUTTERFLY ON SOME SUFFOLK REPORTMOTHS 2009 2009

59

Annex D. Dingy Skipper Survey, 2009 Overview The Dingy Skipper may have been permanently lost from the formerly strong site at RAF Barnham, and from the smaller colony at Center Parcs Elveden. This year’s survey shows that the colony in King’s Forest is still breeding in the area around the Archery ranges, and still flying more widely in the forest. Nonetheless, with this as the only remaining colony in Suffolk, there is a strong possibility that it will be lost unless the right habitat is preserved. Fortunately, the Forestry Commission is being very co-operative, and has undertaken felling and clearing operations to benefit the bird’s-foot trefoil and to create suitable areas for egg laying. 2009 Survey The survey involved 18 recorders, and 36 man-days, but searches at Center Parcs and RAF Barnham again failed to find any Dingy Skippers. First flights were noted on the county border earlier than usual, along the Devil’s Dyke on 22 Apr, and in the King’s Forest on 1 May (a week’s delay is normal). The highest count was achieved in good weather on 23 May. The latest sighting was on 29 May, after which cool wet weather prevailed. Another year without any sightings at RAF Barnham or Center Parcs is of grave concern. The Dingy Skipper has lost ground and if the colonies at these two sites have been extinguished, the King’s Forest is now the only remaining Suffolk population. Even there, the original Wordwell ride again produced only a single sighting. The sites visited are listed below, with more detail. This year’s effort was concentrated on defining the breeding area within the King’s Forest, with a view to extending the suitable habitat. RAF Barnham TL8580/8680 – Two visits were made in suitable weather on 7 and 20 May, but not a single Dingy Skipper was seen. Very little bird’s-foot trefoil was present, and the grazed habitat looked unpromising, a large proportion of the former flight area being shaded out. It seems increasingly likely that the Dingy Skipper has been lost from the SSSI. Last seen here in 2005. Center Parcs, Elveden TL810805 – This isolated colony existed on a small site that has been losing its suitable habitat to a build up of coarse grass. Several experimental strips have been cut/rotovated close to the flight area, and more will be prepared this autumn, with a view to extending the growth of bird’s-foot trefoil. Center Parcs staff visited the area almost daily in May, without seeing any Dingy Skippers. On 20 May, a longer search was conducted in good weather, but three pairs of eyes, including BC’s Eastern Region Conservation Officer, failed again. Last seen here in 2006. In King’s Forest (overall): First found 1 May (twelve days earlier than 2008). Best count: 18 on 23 May. Latest sighting: 29 May (at least five still flying). Extent: two core breeding tetrads, with occasional strays in three outlying tetrads.

Trans. Suffolk Nat. Soc. 46 (2010)

60

Suffolk Natural History, Vol. 46

King’s – Chalk Lane area (TL8275 & 8374) A couple of singletons were seen on the parallel path just north of Chalk Lane, but shelter is lacking, and this does not appear to be a breeding area. King’s – Archery Restricted area TL833737 The secluded open area between the mature beech to north and plantation to south seems to be the main breeding site (TL834739), and two eggs were found here on 29 May. The northern margin of the east-west ride south of the Archery hut is productive when the wind is northerly. Following the mowing of the eastern margin, the north-south conservation ride (205) bounding the archery restricted block is looking very promising, and at least five were flying here on 23 May. Sightings have also been made on the eastwards extension of the east-west ride (204) to TL836735. The highest one-day count in this area was 18 on 23 May. King’s – Griffin’s Covert (East of Archery area) Occasional sightings have again been made in the area known as Griffin’s Covert. The ride extends east into the next tetrad, and on 1 May, three were seen flying just into that potentially suitable habitat to the east (TL8472) King’s – Wordwell area TL834733 Conservation felling has widened the main ride by 30 m since last year, and this will allow more sunlight into the strip where the bird’s-foot trefoil grows. The stumps have yet to be lifted, and it is hoped that this will create a rough, undulating area where the plant can flourish in hollows suitable for egg laying. This year, the bird’s-foot trefoil was flowering nicely at the south end of the main ride, and along the E-W access ride. Nonetheless, there is little evidence that Dingy Skipper is still using this area – only one sighting being made in the sheltered glade off the main ride. There was only one in 2008 too, and it is some years since they were present in numbers. King’s – West of B1106 Encouragingly, there were two sightings to the west of the road, both relatively early in the flight period (Ride 201 at TL820757 on 1 May, and south of Ride 206 at TL817728 on 10 May). Elsewhere, negative searches were conducted along several of the sites where Lotus corniculatus was found last year. Total Tetrad Cover Although three tetrads have been lost over the past five years (RAF Barnham and Elveden together), good results in the King’s Forest have produced sightings from three outlying tetrads. Confusingly, this results in constantlooking tetrad counts over the same period.

Trans. Suffolk Nat. Soc. 46 (2010)

NOTES BUTTERFLY ON SOME SUFFOLK REPORTMOTHS 2009 2009

61

Annex E. White-letter Hairstreak – 2009 Following a good season last year, 2009 turned out to be a poor year for White-letter Hairstreak sightings. July was not blazing hot, and it proved difficult for observers to find the adults, even in normally dependable colonies. It was found in only 16 tetrads (2·5% of the 645 surveyed), compared with 24 (4·6% of 547) in 2008. This reflects the reality that the adult insects remained in the elm canopy and did not descend to take nectar in places where they could be seen. It does not necessarily suggest that colonies declined. Indeed, over the past five years, it has been recorded from 79 tetrads, 7% of the whole county – and this is rather pleasing for any UK BAP species. The future of the White-letter Hairstreak in Britain is viewed with some concern largely because of the uncertain consequences of Dutch Elm Disease. Yet it remains an under-recorded species that can be found in most places where elm survives whenever intensive effort is put into a search. A nationwide survey during 2008/2009 rather proved this point by finding the butterfly (or its early stages) within a few kilometres of most of the randomly selected squares. In Suffolk, it is being found at many stretches of elm along roadsides or in hedgerows, where they are merely transient populations as distinct to well-established colonies. Annex F. White Admiral 2009 White Admiral is apparently expanding in Suffolk woodlands. It has been noted in 71 tetrads (7% of the county) in the past five years, compared with just 13 (1%) in the 1983–1985 survey. The situation here is more favourable than in the UK as a whole, where its decline resulted in its being added to the UK BAP priority list in 2007. It inhabits damp woods with plenty of honeysuckle, and seems to have settled recently in several smaller woods that are not longstanding colonies. It is known that unofficial releases have been conducted in Dunwich and Tunstall Forests over a period of years (and probably in Theberton Woods too). Over the same period, climate change appears to have had a beneficial effect, and second generation emergences have been noted in good years (but not 2009). Progressive recording efforts have resulted in an increase in the tetrad count, but not all of the sightings indicate permanent colonization. Nonetheless, the past five years have produced good numbers, and it is encouraging to have a UK BAP species doing so well in Suffolk. In 2009, White Admiral was recorded from 26 tetrads (4% of the 645 covered) – less than in 2008, but nonetheless very satisfactory. Annex G. Grayling 2009 Added to the UK BAP Priority species list in 2007, the Grayling has lost 45% of its UK distribution over the past 30 years, and is now essentially a coastal species. Losses have been no less dramatic in Suffolk, and it is now very localised in its favourite Breckland haunts and extremely rare in Mid Suffolk, although it remains widespread in the Sandlings.

Trans. Suffolk Nat. Soc. 46 (2010)

62

Suffolk Natural History, Vol. 46

The Grayling is an insect of dry sandy grassland, and has a generally coastal distribution. It also has a fondness for conifers on dry sandy heathland, and can still be found in the Brecks as well as the margins of Dunwich, Tunstall and Rendlesham forests. Formerly, it was regularly found in the general countryside too, but the agricultural clay of High Suffolk no longer supports it, and the distribution maps have thinned out, with few sightings outside of the prime areas of Suffolk Coastal district. The trend illustrated in last year’s report continues, and the colonies in the Brecks are isolated. Yet in 2009 Grayling was still found in 10% of the county, thanks to a better-than-average showing. It is still recorded on three transects (Cavenham Heath in the Brecks, Fynn Valley and North Warren), but numbers are moving differently at each site. A gentle long term decline is evident at Cavenham Heath, the index was just two Graylings this year at Fynn Valley, and North Warren recorded an outstandingly good year, with a remarkable 472. Rob Parker 66 Cornfield Road Bury St Edmunds Suffolk IP33 3BN

Trans. Suffolk Nat. Soc. 46 (2010)