Many thanks to Deborah Dunn for reporting data on the daily number of exuviae at her garden pond in Steeple Aston.
The plot below compares the numbers of exuviae she found daily in 2020 with those in 2021. This shows that the exuviae were 14 days later, on average, this year, compared with 2020. Also the total number counted this year (29) were well down on last years impressive total of 40 (the pond is only 2.5m x 1.0m with a maximum depth of 0.4m).
It is really useful to have these observations which provide some quantitative data on Southern Hawker emergences. It certainly confirms subjective impressions that the season was much later to get going this year than in the exceptionally early one last year. It is interesting to see this effect is present for a mid-season species such as Southern Hawker, as well as the early ones.
Examples of "hard" numbers which allow quantitative monitoring of changes in numbers and timing in the dragonfly field are few and far between, so I feel this is an especially valuable study.
It is great to hear that Deborah is planning to continue her observations in future, and it will be fascinating to see what trends emerge!
Click on the image to get a larger, clearer version.
Stephen Burch
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| Daily counts of Southern Hawker exuviae in 2020 and 2021 |
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| The pond from which all these Southern Hawkers emerged! |
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