Brown Hairstreak Spotting

Brown Hairstreaks event, West Williamston nature reserve

On the 15 and 16th of August, avid butterfly enthusiasts descended on the Wildlife Trust of South and West Wale’s nature reserve at West Williamston to look for brown hairstreak butterflies.

The first aim was to record as many individual adults (in one day) as possible to help in trying to assess the size of the overall population. The second aim was to continue to look for ‘assembly’ trees by recording early morning males, and which trees they were in.

On the first day 28 brown hairstreaks were observed – a record for the site in one day. This figure has been humbled slightly by receiving a report that on the same day another count was taking place at a site in Hampshire where 76 were recorded in 2 hours! So there is a challenge for the next Hairstreak Weekend in 2016.

The 28 recorded were mainly males up in the canopy of ashes but 5 were low level females of which 3 were observed egg laying.

Day 2 was a shadow of Day 1 with only 10 brown hairstreaks seen, all up in the canopy of ashes and relatively lethargic with definitely no more egg laying.

The weather on the two days was similar although this is typical hairstreak behaviour – one day all guns blazing, the next spent in harbour refuelling.

However to fly the flag for West Williamston (one of the UK’s best sites for this species) the reserve may have produced the first record of egg laying in 2015 in the UK.

Nectaring brown hairstreak on hemp agrimony - Cr. Maggie Sproule

Nectaring brown hairstreak on hemp agrimony – Cr. Maggie Sproule

Those wishing to catch up on their brown hairstreaks still have time – the latest ever adult sighting at West Williamston was on the 5th of October in 2013 by David Moore. The Wildlife Trust reserve at Teifi Marshes is also another good site for brown hairstreaks.

This year they have been seen feeding on hemp agrimony. This is apparently the only site in Wales where nectaring brown hairstreaks have been seen.

A big thank you must be extended to David Redhead, the county’s butterfly recorder and Nikki Anderson, the voluntary warden for West Williamston who were both instrumental in organising the event and who continue to champion the surveying for the brown hairstreak at this reserve.

Nathan Walton
Wildlife Trust Officer, Pembrokeshire