Nationally, the adult season began in May with a few butterflies believed to be hybrids between Chalkhill Blue and Adonis Blue (L bellargus). None of these was in the UTB area. Our region's first report (29th June, Berkshire), was also the first in the UK and though this solitary butterfly was followed very quickly by a sprinkling of sightings across the south of the UK, it was some 20 days ahead of a more general emergence locally.

Chalkhill Blues
Photo © Nick Bowles

This general emergence was quite obviously ordered according to orientation of the site. Steep slopes facing south were invariably first and those facing north east last. Equally these sites with south facing slopes managed to retain adults far longer than the less suitable sites (with the last sighting on the 22nd September in Buckinghamshire). So this season's flight period lasted approximately as usual, being only slightly shorter, despite very poor weather and lower numbers of Chalkhill Blue. Early indications from transect reports suggest that the numbers of Chalkhill Blue butterflies were reduced by half and that those sites which have marginally suitable habitats had even less than this.

Planting Horseshoe Vetch
Photo © Nick Bowles

Under these circumstances it might have been expected that there would have been some weaker colonies where absolutely no Chalkhill Blue were seen. This doesn't seem to have happened (though not every site was visited) and we actually added two new locations to our list of known sites. 2007 was a poor year for the species and we might see a knock-on effect over the next few years. Sites, where the temperature of microclimates is lower, may suffer with smaller populations. Intervention to ensure sympathetic management (to maximise the potential for successful development of larvae) will be very helpful.

Planting Horseshoe vetch (H. comosa) into our Holtspur Bottom reserve in the hope of establishing a new Chalkhill Blue colony.

The 2006 records of Chalkhill Blue in the UTB area (from Levana).