Monitoring the abundance of a canopy-dwelling butterfly species
direction and was in the sunshine for the majority of the day. No incidences of Dutch Elm Disease
occurred at Sites B, C and D. The vegetation at these sites was dominated by U. carpinifolia, a
species of elm that has good resistance to the disease (Coleman 1998). The impact of Dutch Elm
Disease on colonies of S. w-album is difficult to assess. Many variables need to be taken into
consideration; for instance the number, height and species of elm tree, and the amount of sunshine at
each site. It would be possible to enhance our knowledge on the impact of varying degrees of Dutch
Elm Disease on the abundance of S. w-album if the sites on the fixed time observation point route
were monitored for several years.
As S. w-album is a sedentary species, it will not readily colonise new areas when its existing colony
is destroyed by Dutch Elm Disease; it has a closed population and will therefore be prone to local
extinctions. Conservation management can help to reduce these extinctions by maintaining suitable
wildlife corridors to assist colonisation, and by protecting or creating suitable habitats in the vicinity
of the existing colony. A monitoring method that has been developed specifically to monitor a
certain species of butterfly will lead to more comprehensive results, and enable our knowledge of
that species to be enhanced. The fixed time observation point method used in this study has provided
further information on the abundance and habitat requirements of 5. w-album at Langdon Nature
Reserve. Carried out over a number of years on a wide variety of habitats across the country, it is
likely that it would substantially increase our knowledge of this species.
In conclusion, canopy dwelling species are under-recorded. Consequently, it is important to develop
monitoring schemes that record them more effectively. The S. w-album fixed time observation point
method used in this study is one such method to monitor canopy dwelling butterflies. Indeed, if a
separate method for canopy butterflies is used while monitoring, it may result in a reappraisal of
their status in conservation management.
Acknowledgements
The authors would like to express their gratitude to the staff and volunteers at Langdon Nature
Reserve and the members of the Essex and Cambridgeshire Branch of Butterfly Conservation.
Particular acknowledgement is made to Graham Bailey (Butterfly Conservation) and Nigel Wood
(Warden. Langdon Nature Reserve).
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