The exceptionally warm and dry April of 2007 coincided with, and almost certainly contributed to, the very early emergence of several butterfly species including the Green Hairstreak. April 2008, however, was the coldest since 2001 and from the 5th to the 16th northerly winds brought increasingly wintry weather including a period of sleet and snow during which depths of 5 to 10cm were reported widely.

The earliest national Green Hairstreak sighting was on April 14th at Magdalen Down in Hampshire and the first Upper Thames record was at Sands Bank on the western outskirts of High Wycombe on April 25th. The last week of April was marked by westerly winds which brought spells of rain and showers some of which were heavy and thundery with hail. It's hardly surprising therefore that the next Green Hairstreak sightings had to wait until May 3rd from several locations from Dancersend to Wytham Woods.

Green Hairstreak
Photo © Wendy Campbell

The area around Ivinghoe Beacon and Pitstone Hill provided a hot spot when on May 5th 14 were seen, to be followed by an astonishing total of 41 on the 7th including 34 on just one small area of Pitstone Hill. For the next two weeks of May, sightings were regular but in low single figures with the exceptions of Hartslock, Swyncombe Down and Aston Upthorpe. The final week was marked by low pressure close to the UK giving showers or longer spells of rain and strong easterly winds at times. There were no reported sightings on the 26th, 27th and 28th.

The unsettled spell continued into the first week of June with Benson recording 40mm of rain in one 24 hour period. The first recorded sighting in that month was not until the 6th at Cadsden. Thereafter there followed sporadic sightings at Seven Barrows, Swyncombe Down and Grangelands. The final record of the season came on the 21st from near Little Frieth south west of High Wycombe.

Green Hairstreak
Photo © Tom Stevenson

Despite the very variable weather conditions I think it is possible, with reservations, to conclude that the Green Hairstreak had quite a good season. There were approximately 200 individual butterflies detailed within 61 reports, whereas in 2007 approximately 250 individuals were detailed within 91 reports. By comparison 2006 was a very poor year with approximately 140 individuals from 75 reports.

As far as I can tell there are no new 2km squares to add to the range of the Green Hairstreak but one welcome new site. This is Paices Wood near Aldermaston, a former gravel extraction site, which has been developed into country parkland for the benefit of the local community. There is apparently a good range of butterflies to be seen here including in 2008, for the first time, the Green Hairstreak.

Thanks also to one of our friends from the Hants branch who reported a single Green Hairstreak at Combe Wood near Linkenholt which is just about the most southerly point of our region.

The 2006 distribution of Green Hairstreak (data from Levana.)

Tony Croft
26/01/09