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Brown Hairstreak in Worcestershire - Bulletin 14

August 2005

Dear Brown Hairstreakers,

Now that we are reaching the end of the main season for male Brown Hairstreaks, it is probably a good time to summarise what we have learned so far about the butterfly's use of assembly trees. I suppose our first lesson is that, as far as looking for males is concerned, we need to start even earlier. Our first record this year was 31st July but, given that we saw a female as well as males on this day, this suggests that the season for males probably started at least a week earlier. Secondly, we have now some evidence to suggest that the same tree or group of trees are used in consecutive years. The first two trees where we found adults this year were also definitely occupied in 2004. Thirdly, where groups of trees are involved, there is some suggestion that butterflies move from tree to tree, possibly in response to honeydew shortages. A good example of this was the sighting on 23rd August by John Tilt of three adults in an ash just 20 yards from the assembly tree where Rob Mabbett had drawn a blank three days earlier (see Bulletin 13). Fourthly, it would appear that females spend some time in the assembly trees before dispersal and that a Brown Hairstreak high in the canopy can be either gender. Fifthly, we are beginning to get some feel of the characteristics of an assembly tree. Size seems less important than prominence and location. Most of the assembly trees we have identified so far tend to be at lower altitude than the colony as a whole which squares with the observations made by Jeremy Thomas in his original study of the Brown Hairstreak. Finally, our first sightings of eggs this year have been in close proximity to assembly trees which may be a good method of locating such trees in the future. It seems logical that the highest density of eggs are likely to be found closest to where breeding takes place.

Egg-laying is now well underway and a number of people have reported seeing females at low level over the last week. Ron Hatton saw several Brown Hairstreaks in the orchard to the west of Grafton Wood on 21st and watched a female egg-laying there. He also spoke to another observer who had seen further Brown Hairstreaks that day on the south side of the wood. It is good to also hear of adult sightings away from the usual hotspots. Andy Harris and Alys Duggan from the Worcestershire Wildlife Trust have passed on a record on 25th of an adult plus two eggs at Stockwood Meadows, which is a Plantlife reserve not far from Inkberrow. A group from the Trust were there doing blackthorn management work to benefit the Brown Hairstreak so this was a good reward for their labour. West Midlands Butterfly Conservation strongly recommend management during late July and early August as this is the only time of the year when the none of the life stages of the butterfly are present on the blackthorn. Two areas of blackthorn have also been cut on the edge of Grafton Wood this year within the orchard and on the south side. Both areas are fenced against rabbits and deer to allow good regeneration to take place. On 27th, I revisited all the assembly trees at Grafton in warm but overcast conditions and failed to see any activity. I also walked up the eastern side of the wood and again drew a blank, but did manage to identify a couple of ash trees which looked promising for further observation next year. The sun eventually came out about 3.30 pm and I was pleased to record Brown Argus and a single Brown Hairstreak in flight as I walked through the orchard.

A final reminder of the Local Champions Day next Sunday, 4th September meeting at the Three Parishes Hall, Grafton Flyford (just off the A422 Worcester - Alcester road next to Grafton Church). We meet at the Hall at 10.00 am for coffee and a quick update on the Hedgerows for Hairstreaks project followed by a walk down to Grafton Wood, hopefully (weather and good fortune permitting) to see the butterfly on the wing. Please bring binoculars and telescopes if you have them.

Mike Williams,
Brown Hairstreak Species Champion