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Brown Hairstreak in Worcestershire - Bulletin 38

January 2007

Dear Brownhairstreakers,

Thanks to a really good turnout on New Year's Eve, plus some sterling follow up work by Rob & Rose Mabbett, John Coates and Chris Wiltshire, I am pleased to report that the core area egg count is now virtually complete. There is just one hedgerow to the east of Grafton Wood to complete at our last planned public count this coming Sunday, 21st January and then we are footloose and fancy free! The count overall has produced a very similar total to the previous winter: 590 eggs so far against 578 last year. Given the considerable increase in the number of adult sightings last Autumn, this is perhaps surprising, but we have noticed before that there appears to be no relationship between the number of adults recorded and the consequent egg count. I suspect that the number of eggs laid within a given area is in fact more a reflection of the quality of the habitat available than the number of adults and this is borne out if we examine the individual hedgerow counts. Thus, the southern edge of Grafton Wood, where there is a considerable amount of young regenerating blackthorn available, saw an almost 100% increase in the number of eggs compared to last year, while the 'island' in the orchard, half of which is newly cut and the other half over-mature thereby offering little suitable habitat, provided a sharp fall in egg numbers. Correct management is certainly the key and local wood owner Bob Steele, who has put a lot of effort into Brown Hairstreak management over the years, will I am sure be delighted to know that his egg count this year was the highest ever recorded. Rotational management is not the whole story, however, and location also plays its part, with some hedgerows generally holding good numbers of eggs every season almost irrespective of their condition. This may be related to the proximity of these hedgerows to assembly trees where females congregate for mating with the resident males but we need much more data before we can make any confident assertions that this is the case.

One thing that is very poorly understood with the Brown Hairstreak are the factors causing dispersal. Was it the case that a period of prolonged sunny weather in August/September 2006 meant that adults were more likely to fly away from their core breeding areas close to the woodland edge into the surrounding countryside? Certainly, the two eggs found in the most recent 1km squares added to the distribution map (SO9458 and SO9156) were both some distance from any woodland. In fact, both finds demonstrate the tremendous abilities the females possess at finding blackthorn. The first in Himbleton village was on an isolated roadside patch of blackthorn while the second, which I recorded last weekend, was on a small piece of blackthorn growing within a long hedgerow that was predominantly hawthorn. The continuing perversity of the species was evidenced by the fact that a subsequent search of a nearby hedge that was virtually 100% blackthorn produced not a single egg!

Hopefully, we can put some of these theories to the test this coming weekend as we should be able to finish off the remaining core hedgerow fairly quickly and then launch into some further square bashing activities. Two very obvious holes in the current distribution map (see attached, with thanks to Nigel Stone) are the squares centred on Crowle village (SO9256) and the square just to the east of Inkberrow (SP0257). These would be very good targets for some of our local champions to fill. Just in case anyone has forgotten what Brown Hairstreak eggs look like (as if!), I am attaching an excellent photo of a double taken by Les Clarke, one of our newly recruited Champions, who joined in for the first time on our December foray. Another promising area for further investigation is the M5 corridor east of Droitwich. After the discovery of an adult almost next door to the motorway last September, it would be interesting to see if we could find eggs in this area. A very useful new contact for Butterfly Conservation's Hedgerows for Hairstreaks project is the Highways Agency who are responsible for the motorway and other trunk roads in the county. Andrew Brett plus a couple of colleagues attended the New Year's Eve egg count and he expressed willingness to consider the idea of introducing blackthorn planting onto motorway embankments. So finding eggs in this area could potentially bring about direct conservation benefits.

The meeting place and time on Sunday, 21st January is 10.00 am outside Grafton Flyford Church and I look forward to seeing people there especially those local champions that have not yet been able to support our previous two counts. The weather forecast for Sunday sounds rather more encouraging so hopefully we will have a good day.

Mike Williams,
Brown Hairstreak Species Champion