2010 Butterfly Report

2010 Butterfly Conservation Report

Rob Parker gives an overview of the butterfly season, presented as a slide show at the AGM

The year began with a relatively harsh winter, with persistent heavy frosts and strong winds which killed tender plants and will have had a significant impact on overwintering eggs, larvae & pupae. Nonetheless, spring butterflies appeared in reasonable numbers, and the first impression was that all was okay. In the longer term, the year has been something of a Curate’s Egg – good in parts, but very flat otherwise. Most of our common butterflies had a mediocre season, yet some of our BAP species had a really good year.

Dingy Skipper Survey. Once again, none was found at Center Parcs or at RAF Barnham. On the other hand, there were 2 causes for optimism. The flight area in the east side of King’s Forest seems to have extended, and work to improve the habitat there continues. Unexpectedly, Sharon Hearle came across 4 Dingy Skippers flying in a young plantation in the south part of the Thetford Forest. This lies just north of the old Marmansgrave Wood site, and is only a mile from RAF Barnham.

Silver-studded Blue. The annual survey counted over 7000 S-sBs – with good results at the larger sites. Especially pleasing were an expanding colony in Minsmere’s reversion field, and at the southern edge of the Dunwich Forest, where the Westleton Heath colony has quickly re-colonised a forest compartment felled by the RSPB specifically to allow heathland regeneration. The colony we translocated to Blaxhall Common in 2007 also had its best-ever year, with a peak of 31 butterflies counted during the 6-week period they were flying on the transect. At the other end of the scale, visits to Purdis Heath never found more than 3, re-affirming the importance of extending our efforts to improve the deteriorating habitat before the colony is completely extinguished. Neil Ravenscroft’s survey highlighted the decline of the flight area over 20 years, and we now plan a conservation project for the benefit of all the Ipswich heaths.

White-letter Hairstreak. The hot drought days of July proved to be perfect for inducing White-letter Hairstreaks down from the elm canopy to find nectar at bramble and thistle. Six recorders managed to photograph them in gardens and at spots not known as established colonies, and a dedicated search re-discovered them at the SWT reserve in Bloodhill Quarry.

White Admiral. This was a pleasingly strong year, with good numbers at many of the known sites and no less than 12 reports of White Admirals dispersing to places not usually considered to be host colonies. One almost black specimen of ab. obliterae was photographed by Jon King on the Hadleigh railway line walk, and another by Mervyn Crawford in Mildenhall woods.

Silver-washed Fritillary. Undoubtedly the

highlight of the season was the spread of Silver-washed Fritillary from a couple of tentative footholds to no less than 9 places in Suffolk. Of these, 6 are woods with violets and some chance of providing breeding habitat. Essex, Cambs and Norfolk all experienced this dispersal event, and there is hope that the species will stay –it has been considered absent since 1969.

Conservation Advice. Site-specific butterfly conservation advice has been provided to the Sotterley Estate, the SWT reserve at Cubbitt’s Pit in the Bloodhill Quarry and to the management at Pakenham Wood. All 3 sites host BAP species, and White Admiral, White-letter Hairstreak and Silver-washed Fritillary put in appearances during the advice & monitoring phase.

Transects. Richard Stewart’s transect in the Fynn valley is being discontinued after a ten-year run, but has been replaced by new walks in the Dunwich Forest and Arger Fen. They will have had an unspectacular first year, but an adequate baseline to monitor the changes that both sites are about to undergo. Dunwich Forest has some special promise, as both Grayling and White Admiral are seen on the transect route, a useful new tool for monitoring our BAP species.

Swallowtail and Oddities. There was a higher-than-usual incidence of Swallowtail sightings from Milden in the south of the county to Beccles in the north. At least some of these were explained as accidental releases of captive-bred specimens, and this makes it impossible to declare which of them might have been wild vagrants. Marbled White and Heath Fritillary both put in appearances in Ipswich’s Landseer Park, and as the latter must be the result of a misguided release, doubt is thrown on the validity of the first. One Long-tailed Blue was more likely to have arrived as a caterpillar in a packet of peas, than to have flown in on its own wings.

Recording. The start of a new 5-year period has already brought in some interesting records for White Admiral, White-letter Hairstreak and Silver-washed Fritillary. As peoples’ end of season records come in we are making inroads into our new distribution map. I think we would do well to make a special effort to find Grayling next year – there have been very few in West Suffolk this season.

Events in 2011

Check our website early in the new year as our programme of events will be available there. The green events card will be mailed, as usual, with the Spring edition of The Suffolk Argus.