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Brown Hairstreak in Worcestershire - Bulletin 44

June 2007

Dear Brownhairstreakers,

 The countdown to the new Brown Hairstreak season is now underway.  Looking back through our records, the first week in August seems typical for the earliest sightings in Worcestershire which is a little later than our colleagues in Upper Thames branch of Butterfly Conservation who, over the last three years, have recorded their first Brown Hairstreak well before the end of July (21st July in 2006).  With the kind of dreadful weather we have experienced over the last month, it is very difficult to judge quite where we are with this particular butterfly season.  As noted in the previous ebulletin, the good weather in the spring meant that Brown Hairstreak caterpillars were very advanced compared to the previous year.  The average length of larvae found on 28th May, 2006 was just 6.6 mm while on 19th May this year, over a week earlier, a similar sample of caterpillars were already measuring an average of 9.4 mm.  Whether this growth rate was sustained with the deterioration of the weather in June and whether caterpillars subsequently reached maturity any earlier is impossible to judge.  I was only able to find two caterpillars on 10th June: the highly mobile 'David' around 3-4 foot away from his previous position and now 15 mm in length, and a brand new caterpillar 'Ivy' just slightly larger at 16 mm.  Generally with butterflies, the larval stage is a very vulnerable time in the insect's life cycle and if, as a result of favourable weather conditions, caterpillars are able to feed up quickly then there are fewer losses to predation and, in theory, adults will emerge earlier and in higher numbers.  With the Brown Hairstreak, however, we know from the classic study undertaken by Dr. Jeremy Thomas some thirty years ago that there are also high losses to small mammals and beetles at the pupal stage so like so many aspects of natural history it is as always a question of "wait and see". 

 For those keen on breaking records, the first chance is this coming Sunday, 22nd July when Grafton Wood hosts a Butterflies, Bugs and Botany Day starting at 10.30 am and going on to 4.00 pm.  This is a new event for the reserve which is organised as part of national Save our Butterflies week and replaces our normal open day which we have previously held in the spring (for further events planned for the region see www.westmidlandsbutterflyconservation.org.uk).  Even if it proves too early to see Brown Hairstreaks this year, there should be plenty of other things of interest on the wing including White Admirals and hopefully Silver-washed Fritillary.  Experts will be available throughout the day to lead guided walks around the wood and refreshments will be available in the Three Parishes Village Hall adjacent to Grafton Flyford church together with various displays.  So plenty to see and do whatever the weather.  For further information contact John Tilt on 01386 792458.  An opportunity to hopefully spot male Brown Hairstreaks on their assembly trees takes place a fortnight later on Sunday, 5th August meeting again at the church.  There has been some suggestion that activity around trees is greater earlier in the day so, as an experiment, we plan to meet at 9.00 am.  If you are able to come along, please bring binoculars and a telescope if you have them.  This will be a morning only event and we plan to get back to the car park by 1.00 pm at the latest.  Finally, for those local champions keen to get involved in some practical management to support the Brown Hairstreak, we shall be having our annual 'blackthorn (cider) bash' at Bob Steele's wood on Sunday, 12th August meeting at 10.00 am at Grafton Flyford church.  If you are intending on coming along to this event, please be punctual as we shall be moving on by car.  Please bring something to eat and drink with you, although there will be liquid refreshments available.  As usual, there will be opportunities to have a walk round the wood after lunch and hopefully spot a Brown Hairstreak or two if we are lucky.

 Hope to see many of you in the coming weeks and good hairstreak hunting!  Keep me posted with any early sightings or other Brown Hairstreak related news. 

 Mike Williams,

Brown Hairstreak Species Champion