The Brown Hairstreak Butterfly in North Wiltshire

The Braydon Forest , located between Malmesbury and Swindon , is one of two areas where the elusive Brown Hairstreak is found in Wiltshire. The other is around Cholderton, Tidworth and Porton Down, straddling the Wiltshire-Hampshire border.

A group of volunteers has been monitoring the butterfly in the Braydon Forest area for a number of years by searching between November and March for the white, pinhead-sized eggs, which are located in characteristic positions on the leafless blackthorn. There have been three objectives.

•  To establish the range of the butterfly by systematically searching 1 km squares.

•  To identify 'hot spots' - sites with a high density of eggs, indicative of separate colonies, and to monitor these, year on year, to establish how the butterfly is faring.

•  To monitor sites where eggs are present in reasonable numbers, notably Wiltshire Wildlife Trust reserves, to give feedback and guidance on appropriate hedgerow management.

To date, eggs have been found in 81 one kilometre squares in an area extending 13 x 11 km as shown on the accompanying grid, which also includes squares where searches have been unsuccessful. Somerford Common is marked as SC .

A timetable of searches for the 2008-2009 winter is also included. If you would like to help on any of these dates, please get in touch with me.

Michael Sammes

 

 

------------------------------------------------------------------------------------------------------------------------------------------------------------

 

How did Wiltshire's Butterflies fare this year?

This spreadsheet below indicates changes in abundance for the Transect Monitored Sites in Wiltshire 2008 compared to 2007

It is assumed that increases or decreases greater than 20% are significant.

Species in bold type are where the sum of the 'No change' plus 'increase' exceeds the 'decrease' and are considered to have had a relatively good season in 2008.

For some species marked with an * the data is unreliable due to the small number of butterflies seen on transect.

For the Purple Hairstreak, I only use my data (Mike Fuller) obtained from the evening transect walk, when much larger numbers of butterflies are seen (>100 at peak flight period), making for a more accurate Index of Abundance