Counting dragonflies

In a previous article, I described how we, as citizen scientists, can help track changes to the natural environment by contributing data on the distribution or abundance of species to various monitoring schemes. In this article, I want to show how we are doing this with respect to one of the main groups of species that Foxearth Meadows is most important for – its damselflies and dragonflies.

When A Rocha UK took on the management of this wonderful site, David Chandler and I, who were both ARUK Trustees at the time, put our heads together to consider how we could monitor the dragonflies’ populations that were there. We wanted to be able to track changes in the abundance of these species at the site to see if the management and protection at the site was making a difference for these beautiful creatures. In doing so, we took advantage of being able to draw on some draft guidance produced by the British Dragonfly Society (BDS) for monitoring dragonflies and adapted this for our own purposes. We set-up a number of locations at Foxearth Meadows where we counted adult dragonflies and damselflies once a month, from May through to September, along fixed routes called line-transects.

Whilst we could simply have just tracked changes in the numbers at Foxearth Meadows, which would have told us what was happening at the site, it was important to be able to compare that with changes that were happening elsewhere in the surrounding area, by way of comparison. So we also identified a growing number of rivers, ponds and lakes across West Suffolk from Clare in the south to Thetford in the north, and set-up either transects or point locations (fixed points where we could stand, watch and count) to make these counts regularly through the summer. I had not done any dragonfly surveys before, but under the advice and guidance of David, set out to familiarise myself with the various species in the area to get started, and I was soon hooked!

Four-spotted chaser (Photo: Albert Butcher)

The first location I started to monitor was a farm pond near Rougham, which I stumbled across one spring whilst out walking with my children after school, and that was absolutely buzzing with damselflies. Although probably not the easiest start, with the help of a relatively cheap digital camera and some patience, I started to be able to separate the species, including the tricky common blue and azure damselflies. On my first proper survey at that site, in June 2015, I counted 31 individuals of six species, and remember particularly enjoying watching territorial male four-spotted chasers chasing each other around the pond. That first year, I concentrated on surveying three main areas as I became more familiar with the different species, and ended up recording 15 species across these locations. This included the willow emerald that has been busy colonising East Anglia since first being observed on the Suffolk coast in 2007. I remember the excitement when I saw two individuals, their long metallic bodies in characteristic hanging position between their outstretched wings, dangling above the pond from the ends of a couple of ash tree branches on the afternoon of 5 September 2015.

Willow emerald (Photo: Albert Butcher)

Importantly, we were able to publish a peer-reviewed paper in the Journal of Insect Conservation in 2020, to show that our methods produce repeatable and meaningful counts of abundance and species richness, which means that we can use these data to track changes through time. We found that weather, particularly temperature, but also wind speed and cloud cover, was a key factor influencing the numbers recorded, but that by noting weather conditions at the time of surveys it was possible to correct, to a certain extent, for the effect of survey conditions upon overall abundances. We also noted that the numbers and species of dragonflies recorded tended to vary significantly between different waterbodies, even at the same site, suggesting that they can provide good measures of the quality of those different waterbodies for different species. Now we have been counting these species for eight years, we are starting to gather a decent long-term trend, and therefore look forward to identifying how well we are doing at conserving these species at Foxearth Meadows. Watch this space for a future article on these longer-term changes.

This article was written by Professor James Pearce-Higgins for the Spring 2023 Foxearth Meadows news and prayer letter. James is Director of Science at the British Trust for Ornithology, an ex- Trustee of A Rocha UK and a member of the Foxearth Meadows Steering Group.