Stephen Burch
Oxfordshire Dragonfly Recorder
Introduction
Marsh Wood Pond is a little known dragonfly site. It consists of a small, narrow strip of water adjacent to Marsh Wood - a minor wood near Wallingford.
This pond has however been the subject of an extensive set of monthly visits made every year since 2017 by one remarkably dedicated observer, Julian Edwards. All his visits were timed to be approximately mid month. During his visits, which covered the entire season from April to October, Julian made systematic records of the odonata he observed, in the standard BDS format. This uses the letter system A (=1), B (=2-5), C (=6-20) etc to provide an indication of the numbers of each species present. Additional letters provide information on breeding activity (ovipositing, tandem pairs etc).
Given the reports of an apparent reduction in the numbers of odonata in Oxfordshire during 2025, and the substantial fall in the numbers of Southern Hawker exuviae at a small garden pond in Steeple Aston already reported, it seemed worthwhile taking a closer look at the Marsh Wood Pond records. As these records were collected systematically in the same way every year since 2017, it seemed not unreasonable to expect that analysis could provide some quantitative information on fluctuations in the odonata present at this site from year to year.
Species present
Before considering annual fluctuations, it is useful to summarise the odonata species recorded year by year in a simple tabular form as shown below. The dark squares show presence of a species recorded during any visit in the indicated year.
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| Species recorded at Marsh Wood Pond by year 2017-2025 |
The total number of species recorded was a creditable 14, given the small pond size and location. However only Azure Damselfly, Brown Hawker and Common Darter were seen every year. Probably the most notable dragonfly was the still somewhat localised Hairy Dragonfly. Only five species of damselfly were seen. It is interesting that the Willow Emerald Damselfly, which only arrived in Oxfordshire in 2019, was first recorded in 2025.
Analysis of annual fluctuations
For the analysis it helped that all these records were available in annual spreadsheet format files which had previously been used for uploading them to iRecord.
Not having performed this sort of analysis previously, it wasn't clear what the best way of summarising these records would be. Hence it seemed worthwhile to look at the following three measures for each year:
- Total number of species recorded annually, with separate counts for dragonflies and damselflies.
- Total number of records provided annually, again with separate counts for dragonflies and damselflies.
- Estimates of the minimum total number of individuals seen each year in all monthly visits (using the lower values of each of the letter abundance codes, i,e, 2 for B, 6 for C etc).
Results
The graphs below how the above measures varied by year from 2017-2025.
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| Variation in the numbers of species seen at Marsh Wood Pond between 2017-2025 |
The above plot shows that only 5 species of dragonfly were seen in 2025, compared with 8 in 2024 and 9 in 2023 (the maximum). The 5 species in 2025 was the lowest total since 2018. Only a few species of damselflies were seen annually at this pond (minimum of 1, maximum of 3). The 2025 figure (3) was boosted by the arrival of a new species - Willow Emerald Damselfly.
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| Variation in the numbers of monthly records from Marsh Wood Pond between 2017-2025 |
In the above plot, the total numbers of records shows a general year on year increase from 2017 to 2024, but with an abrupt decline in 2025, back to levels last reported in 2020. The smaller number of damselfly records show no decline in 2025.
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| Variation in minimum numbers of total individual odonata from Marsh Wood Pond between 2017-2025 |
In the above plot, the minimum number of individual dragonflies recorded annually showed a marked decline between 2024 (60) and 2025 (24 or 40% of the 2024 figure). The 2025 figure is lowest since 2018.
The minimum numbers of damselflies seen each year varied substantially as occasionally high numbers are seen (e.g. 100-500) whereas more usually counts were much lower. Hence, the overall figures tended to be strongly influenced by whether or not these occasional high counts had occurred during the year.
Conclusions from the analysis
From the analysis above, all three measures showed that 2025 was a poor year for dragonflies at Marsh Wood Pond, compared with recent previous years. The most marked decrease was in the minimum total numbers of dragonflies seen which declined to only 40% of the 2024 figure. The decreases seen in 2025 were sufficient to approximately reverse the general increases in species and numbers seen between the start of the survey in 2017 and 2024. Hence the figures for 2025 are similar to those last seen prior to about 2020.
For damselflies, these trends are less clear, perhaps due to the small number of species found combined with the occasional large fluctuations in the numbers present during the monthly survey visits.
Julian Edwards reports that there were no out of the ordinary changes in the state of the pond in 2025 which might have directly contributed to the observed declines. The grass cutting regime on one side of the pond was carried out as usual, and although the water level dropped marginally in mid summer, it was not very different from previously.
The 2025 decrease in odonata in Oxfordshire
The decline in the recorded dragonflies in 2025 for Marsh Wood Pond is in line with the impressions of several observers that 2025 was a poor year for odonata generally in Oxfordshire. The numbers of exuviae recorded from a
small garden pond in Steeple Aston also showed a large decrease this year.
The summer of 2025 was the hottest on record in England and was also notable for drought conditions that persisted for most of the odonata season. However it is unclear what the mechanisms were for causing fewer odonata to be seen given the seemingly ideal conditions for them that persisted for much of the summer.
Nationally, Adrian Parr (who is the Migrant Dragonflies Project Coordinator for the British Dragonfly Society) noted in late July that comments about levels of activity seemed rather varied. Some people were reporting that things in general had been good, but others said it had been quiet.
Adrian suggested then that it may indeed be possible for the weather to have been "too good" on occasion - maybe not always so much for the dragonflies, but for watching them. The dragonflies might have been present but only active near water at times of day when observers wouldn't normally look (i.e. early morning and/or late afternoon/evening).
This accords with my own experience from a site in Scotland several years ago. On my first visit, which was in fine, dry weather, activity was quite high. However the next day it was much hotter and by the time I arrived on-site (mid morning) there was little to be seen. Presumably the species were still present but were just not showing themselves in the heat, unless they had dispersed which is another factor Adrian Parr has mentioned.
However, this mechanism provides no explanation for the drop in Southern Hawker exuviae numbers seen in Steeple Aston this year. Hawkers and most other odonata have multi-year life-cycles so what happened in 2025 isn't necessarily the only factor that's involved in what we've been seeing.
It will be interesting to see if anything more definitive is reported nationally now that the 2025 season has ended.
Whatever the cause of these decreases, let's hope there's a return towards more normal numbers in 2026!
Acknowledgements
Many thanks to Julian Edwards for his extraordinarily diligent monthly record keeping since 2017 and for his very useful comments about the condition of Marsh Wood Pond in 2025.
