Monitoring dragonflies and damselflies in Britain

National surveillance

Mapping the distribution of dragonfly records in atlases illustrates how the known range of species has changed, but it is a blunt instrument for monitoring dragonfly populations at a national or local scale. This is best referred to as surveillance monitoring and requires a regular flow of records from many sites all across Britain. In DragonflyWatch, surveillance is being carried out using information from Site Lists gathered during single visits to dragonfly breeding waters. Periodic status reports will be published on this website. As well as providing national population indices, the results allow Britain to contribute to Europe-wide dragonfly monitoring.

Site monitoringRecording on Skye, Scotland - copyright J. Willet

In order to monitor change at individual sites, however, greater detail is needed and so other methods are more appropriate. Site monitoring needs commitment and concerted input over a number of years in order to obtain meaningful results. The method used needs to be robust to changes in habitat and ideally changes in people, and must be applied consistently. Guidance on how to monitor important dragonfly sites is being reworked by the Conservation Officer following Pilot Monitoring begun in 2012. In the meantime, the following notes should be useful.

Why are you Monitoring?

BDS does not need transect data. We concluded at the end of the Pilot that transect monitoring is useful at the site level for site managers but is does not produce the best data for the BDS Recording Scheme. In relation to monitoring, what BDS needs are either point records from prime spots or records within separate national grid 1km squares (monads) since our computed trend analyses use monads as 'sites'.

Methods for Monitoring

The method doesn't actually matter, as long as it's repeatable throughout the season, from year to year and from recorder to recorder. It may well be that a transect along or around a waterbody is the best way forward. In this case keep separate records for each 1km square. At sites that are difficult to access, timed counts may be a better option. Recorders and site managers need to decide how long to count for, and this will vary according to site. You also need to decide the minimum conditions for counts: temperature, cloud cover, etc. to ensure comparable results.

BDS needs the headline data of species and numbers whereas the site manager needs the detail. All records should ideally go into iRecord using the 'list of dragonflies' form and with the 'Recorded all species?' checkbox ticked to indicate that numbers of all species, not just the unusual ones, seen on that visit have been recorded. Recorders primarily monitoring butterflies or birds may alternatively also record dragonflies using Butterfly Conservation's Butterfly Monitoring Scheme (UKBMS) or BTO's BirdTrack (BT) but dragonfly records from these systems may be slow to reach BDS.

Site evaluation

Monitoring methods are not suitable to determine the value of a site for dragonflies. This is best done by obtaining evidence of presence, abundance and breeding during a series of visits during fine weather. Visits should be spread over the flight season and ideally over several years, to account for annual population fluctuations. The information gathered can be assessed against criteria for Priority Sites (also known as Key Sites).