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          BROWN HAIRSTREAKS BY THE HUNDRED !

(From the Spring 2002 Newsletter)

Searching for adult Hairstreak butterflies or, even worse, trying to photograph them, can often be a frustrating business, as anyone who has tried will confirm.  Green Hairstreaks sit around on Hawthorn bushes for most of the day and remain infuriatingly invisible. Purple Hairstreaks hang about for hours at the top of Oak trees only deigning to fly when everyone has gone home. White letter Hairstreaks only ever descend to ground level while you are changing the film in your camera or when your back is turned.  Black Hairstreaks are found miles away and, whenever you decide to set off to try to see them, it always rains.  And as for Brown Hairstreaks……well they are just next to impossible.  The late Jack Green, who rediscovered the butterfly in Worcestershire in the late 60s, once told me that he had kept a Brown Hairstreak in view for a whole hour during which time it was in flight for less than forty seconds.  Our own annual Brown Hairstreak days, usually centred on our reserve at Grafton Wood, attract enthusiasts from far and wide (this year’s is on 1^st September) and is conducted like a military operation.  After an initial roll call, orders for the day are issued and crack teams are sent out to all points of the compass fully armed (with a mobile phone!), under instruction to ring in to central command when the quarry is sighted.  At this point, a general alert is sounded and all troops head for the rendezvous point by the shortest possible route and in the quickest achievable time.  Over the years, we have fine tuned our campaign to such a degree that the Brown Hairstreaks now give themselves up at the earliest opportunity so that we can all go away happy and they can be left in peace to crawl around blackthorn bushes, and whatever else they get up to, for the rest of the day.  On our last open day, a long suffering female was even prepared to stay put on a small oak tree while it was bent double to bring it within camera range.

If this sounds just too much like hard work or perhaps a little too silly, there is an alternative – you could search for Brown Hairstreak eggs!  Click on the picture below for a better view.

Brown Hairstreak egg hunting it must be admitted is not to everyone’s taste and requires serious levels of patience and a good eye but success can be guaranteed which is more than one can say about searching for the adults.  It also has a serious purpose in that it gives us a good indication of how the butterfly is faring and, in the context of Grafton Wood, whether our management is benefiting the butterfly.  The Worcestershire colony is almost certainly the best monitored in the country with annual egg counts dating back to 1970 and continuing to the present day.  In the early years, relatively few eggs were recorded but, since management around the wood started in earnest in the 90s, numbers have been much higher.  In good years, we have recorded well over 500 eggs just around Grafton Wood itself.  The basic methodology of counting has remained unchanged throughout the past thirty years and we now hold an impressive data set.  Basically, each section of blackthorn is given a code letter and is allocated a search time (person hours) which is kept to each year irrespective of how many volunteers are involved.  For each egg found, a height measurement is taken and it is also noted whether the egg has been laid singly or whether it is part of a larger cluster.  Over the years, this has given us a good insight into the ecology of the butterfly and we have been able to develop management prescriptions based on this knowledge.  We are fortunate that most of the key area falls within the Grafton Wood SSSI and we have been able to secure annual funding from English Nature to pay for cutting of blackthorn stands on rotation by contractors.  This has been supplemented by our own volunteer work teams and, from time to time, various outside groups such as Stourbridge College.   Female Brown Hairstreaks find young regenerating blackthorn very attractive for egg laying and these areas generally produce good counts for the first couple of years after cutting but then begin to decline as the blackthorn thickets again mature.  Within the nature reserve itself, we are also opening up new glades, as well as reintroducing coppice management, to encourage blackthorn and, over the past two years, we have been delighted to record eggs within the main body of the wood as well as along the woodland edge.  Once the core area has been monitored in this way, and if we have time, we have undertaken egg searches of a wider area and have slowly built up a picture of the total distribution of the butterfly in the county.

All this, of course, takes time and resources and there is no doubt even more could be achieved with extra help.  Do come along on 1^st September and join in all the fun but also think about making a commitment to help with the winter egg searches (which can be fun too!).  Full training is on offer and there is the added incentive of hot soup in the local pub at lunchtime.  This year’s count is now well underway and it looks as if 2001/2 is shaping up to be a record year.  By the time this newsletter is published, the core area count should near completion but we will still need help in targeting new areas.  Please get in touch with Trevor Bucknall for full details.  You too can see Brown Hairstreaks by the hundred!

Mike Williams

As a footnote to Mike's article above,  the following picture shows a  group of Brown Hairstreak eggs found during the second hunt of 2003. Normally this butterfly lays eggs as singletons but this year an increased number of  "clutches" have been found. We thought that the West Midlands branch held the record with 5 eggs but the Upper Thames Branch have found a cluster of 6 eggs this year. We could count ours as a 6 also - in the picture you can see a 6th egg just below the side shoot.

Searching for the eggs really brought home to me the devastating effects that unsympathetic habitat management can have on a butterfly population. One hedge that had more than 80 eggs last year had been flailed at the wrong time of year and we only found 1 egg this time around. All is not gloom though as in other parts of the reserve there was a good count and further blackthorn whips are to be planted on 7th February. Please go along and help if you can.

Nigel Stone.