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2012 Butterfly Conservation Report
Autumn 2012
2012 Butterfly Conservation Report
Rob Parker, Conservation Officer (Butterflies) The report was presentedas a slide show at the AGM on the 22ndSeptember 2012, using the photography andartworkofDouglas Hammersley, a talented contributor to ‘The Suffolk Argus’ , who passedaway earlier this year.
Following two rather poor seasons, and beginning with a challenging winter, 2012 did not inherit strong populations of many species. Global weather patterns then intervened, notably irregular jetstreams, and these created chaotic weather which further depleted wild stocks of eggs, larvae, pupae and adult butterflies. The result was an awful butterfly season, typified by the results of the Spring Lane transect at Bury St Edmunds, which produced the worst results in the 13 years it has been walked.
The preliminary analysis covered each of the biodiversity action plan species, the one bright spot of the year, which was the continued success of the Silver-washed Fritillary, and two other items of conservation importance.
Dingy Skipper. The King’s Forest colony was found flying in all the established areas, albeit in weak numbers, and without many sightings of mating or egg-laying. The RAF Barnham and Center Parcs sites were both checked again but confirmed as defunct. Close to Barnham though, the colony on Thetford Heath nature reserve and the margin of the Thetford Forest was still present, and one mating pair was seen. Silver-studded Blue. Emergence dates reverted to 1990’s timing, defeating preplanned dates for the Minsmere count. As a result, the deferred first count was still too early and the second attempt was rained off in the afternoon, so an incomplete weak count was all that was achieved. Similar difficulties were encountered at most other sites, with two notable exceptions. At Walberswick NNR, three searches were mounted in decent weather but not a single Silver-studded Blue was seen; it now looks likely that this colony has been lost. Better news from Blaxhall Common, our 2007 translocation colony, was a highest ever single walk count of 48, and an encouraging spread into the wider offtransect parts of the common.
White-letter Hairstreak. Sightings were down, although this was probably attributable to poor weather reducing sighting opportunities. Where a determined search was conducted, small numbers were seen.
Dingy Skipper Silver-studded Blue
White-letter Hairstreak
Grayling. Judging by casual sightings, Grayling seemed to
have a reasonable season
in West Suffolk, and good
numbers were seen at several of the traditionally strong coastal sites.
White
Admiral. Casual sightings were strong, partly because they were found in many of the woods where searches for Silver-washed Fritillary were being conducted. White Admiral was found in at least two woods with no history of a colony.
Silver-washed Fritillary. The
field event at Pakenham Wood took place in heavy rain on 6th July. The high turnout was a tribute to members’ determination; they learned where to look (and where to observe the owner’s privacy) and were able to return in better weather for some delightful experiences. Several people counted over 20 individual SWFs, and on one occasion 3 separate mating pairs were observed. This bodes well for that colony, and for the species’ chances everywhere else in Suffolk too. Sightings from Bradfield Woods, Wolves Wood and Theberton suggest that breeding colonies may have been established there, and sightings from new woods bring the total up to 17 Suffolk woods where they have put in an appearance. Let’s hope that SWF is back to stay.
Wall Brown Survey.
The joint SNS/BC single-species survey of 2011 was extended into 2012 on the grounds that we were perhaps watching its final decline. Sadly, the results so
far tend to confirm our concern. Most of the sites where they were flying 2, 3 or 4 years ago did not produce any sightings this year. The majority of sightings came from the known strong coastal strip from Shingle Street down to Bawdsey and inland to
Butley. Outliers still exist in the north in the Somerleyton/Lowestoft area and in the north-west at Sedge Fen near Lakenheath. The latter was particularly welcome, although it was just 2 Walls on just one day of the year. Wall is currently suffering a decline across UK, with populations thinning out and becoming more coastal, frequenting only sites in low fertility grassland on well drained sandy soils. It is ironic that our strongest colony sits astride the site just chosen for the landfall of cables bringing electricity ashore from the Anglia ONE offshore wind turbine field.
The Losers. Many species had their
breeding opportunities reduced by
heavy rain during their flight periods and drought or cold during their larval developmental periods. Species suffering particularly badly included Common Blue, Brown Argus, Holly Blue and Small Copper, all of which are double-brooded. The spring generations were thin on the ground, and the late summer generations have been hard to find. Many observers commented on the absence of Vanessids on their buddleja this year, although a brief Indian Summer with a
Grayling
Wall Brown
