The development of a monitoring technique to record the abundance of a canopy-
dwelling butterfly species: Satyrium w-album (Knoch) (White-letter Hairstreak)
ZOE RINGWOOD, ROBIN FIELD, JULIAN HILL AND DAVID MORTIMER
Writtle College, Writtle, Chelmsford, Essex CM1 3RR UK
Abstract
Butterfly species that remain predominantly in the tree canopy, such as Satyrium w-album (White-
letter Hairstreak), may be under-recorded when monitoring using the transect method of the Butterfly
Monitoring Scheme (BMS), as the method does not involve observation of the tree canopy. However,
it is important to use an effective method of monitoring Satyrium w-album, as populations are
vulnerable as a result of the current Dutch Elm Disease epidemic. The aim of the study reported was
to develop a monitoring technique that will take into account the secretive habits of S. w-album
when recording its abundance.
A fixed time observation point monitoring method was developed. The method involved identifying
sites that were known to or could potentially support colonies of S. w-album, and monitoring them by
visual observation of the canopy.
The transect method of the BMS was used in conjunction with a fixed time observation point method;
enabling a comparison to be made. The comparison showed that abundance of S. w-album was
significantly (P