SURVEYS

Meadow Brown butterfly on scabious

Meadow Brown Butterfly on Field Scabious (c) Jo Cartmell

Botanical survey of Fly Ash Pits

This summer (2016), seven members of the Abingdon Naturalists Society spent a few days surveying two of the three pits and their surrounding clay bunds.

You can read the survey here (PDF document).

 

 

 

MORE SURVEYS TO BE DONE AT RADLEY LAKES

Earth Trust has been working with the Centre of Ecology and Hydrology (CEH) to set up butterfly transects on Thrupp Lake and Areas G, H/I and J/P, the areas it manages at Radley Lakes. Transects are fixed routes through the area to be surveyed which are walked regularly and the number of butterflies of each type counted. This data is then fed into the national database, the Butterfly Monitoring Scheme (BMS). As Abingdon Naturalists also do transects, one in Barton Fields and the other in the Nyatt’s Field area, the County Wildlife Site area should be well covered for butterfly surveys.
 
Abingdon Naturalists are also about to start plant surveys on the same Earth Trust managed sites. Their findings will add to the data they have produced for their own site Barton Fields and also the Nyatt’s Field area over the years.

 

Butterflies Surveys at Radley Lakes 

For the past four years, members of Abingdon Naturalists Society have been surveying butterflies in Barton Fields and Nyatt Field. 

Records are made weekly during the six months April to September, taking a circuitous route across the two sites.  These transect records are reported to the UK Butterfly Monitoring Scheme and Butterfly Conservation.

Five recorders share the task of transect walking, providing a great opportunity to keep an eye on other wildlife as well as butterflies.  Over the four years we have accumulated a data set of over seven thousand records of 25 butterfly species.

One finding is that in Nyatt Field, over the four years, there has been a substantial reduction in abundance of the ‘brown’ butterflies, which are grassland species.  Notably, Meadow Brown numbers have reduced by 75% and Ringlet abundance has reduced by 95%.  In contrast, in Barton Fields, numbers of both species have remained stable.


Ringlet Butterfly on Ox-eye Daisy © Jo Cartmell

We ascribe this to winter flooding, particularly during the last two years.  Nyatt Field was under water for weeks at a time whereas in Barton Fields, only parts of the grassland were inundated for shorter periods.  Both species over-winter as caterpillars within tufts of grass, and are likely to drown there, when immersed for prolonged periods.  Further analysis of this phenomenon is required however.

It will be interesting to see how butterfly numbers respond to any flooding or lack of it, this coming winter.

David Guyoncourt
Abingdon Naturalists and FRL Executive