BUTTERFLY CONSERVATION UPPER THAMES BRANCH

Green Hairstreak Report 2007

by Tony Croft

Green Hairstreak
Photo © Tony Croft

In common with several other species in this unusual year in terms of weather, the first reported emergence of the Green Hairstreak was astonishingly early. On March 13 a group of Worcestershire birders who had been invited to Cannock Chase in Staffordshire lured by the prospect of wood larks and Dartford warblers found that the only thing of real interest was a single Green Hairstreak. There have been other March sightings over the years notably one in Devon on March 16 1990 and sightings in Gloucestershire and Lancashire in late March of 2002 and 2003 respectively.

The Cannock Chase record was not a precursor to a general emergence at that time and we had to wait a few more weeks for the first record in the UTB area which was at Grangelands on April 6. This was still very early for our region as in 2006 the first sighting was on April 26 and in 2005 on April 22.

This year’s season was relatively long in that the final record came on June 16 the same as for 2006 although as stated that year’s reporting season did not commence until April 26. The peak seemed to occur around three weeks from emergence which appears to be normal and then activity declined rapidly as May progressed. This was no doubt caused by the extremely wet weather. In April my weather station recorded 1mm of rain. For May, however, the total was 138mm; much of this between the 6^th and the 19^th and then following a more settled spell from the 20^th to the 25^th we had rain and cold winds until the end of the month. Once June started and the weather improved, activity increased again before coming to an end in the middle of the month.

In comparison with the rather poor performance of 2006, with approximately 94 individuals sighted, 2007 was really quite good with approximately 135 seen which is only about 20 fewer than 2005.

The distribution this year was similar to previous years with the Chiltern edge sites well represented but with low numbers per visit whilst Aston Upthorpe and Hartslock further to the south produced relatively high counts. Yoesden Bank together with Sands Bank and Lapland Farm also produced good numbers. The Wytham Wood colony appears stable thanks to the good work which takes place there. There was an interesting report of a sighting at Hurst (SU795729) which lies between the M4 and Twyford. The nearest recognised sites for Green Hairstreak are much further to the east just to the north of Bracknell. I believe the Hurst sighting introduces the Green Hairstreak to a new 2km square.

This butterfly is acknowledged as being difficult to observe due to its size, coloration and elusiveness and is felt generally to be under-recorded, so many thanks to all this season’s reporters for your assistance.

Tony Croft

October 2007