DAVID'S NATURE BLOG

6 AUGUST 2025 – THORLEY WASH

This was an unplanned visit to Thorley Wash. I should have attended a field meeting of the Stort Valley Nature Group at a site near Cannons Mill Lane north of Bishop’s Stortford on the River Stort for the purposes of measuring the water quality and undertaking some river ‘dipping’ for invertebrate life and other things - but my bus didn’t arrive. I didn’t want to be late by waiting for the next due bus as I didn’t know the exact venue on the river, so I decided instead to visit Thorley Wash - which didn’t involve a bus journey.

The morning was sunny and warm, with a stiff breeze which I knew might influence the number of butterfly and dragonfly species; and that was what I experienced as soon as I began travelling along the Stort Navigation, although initially my mood changed when I saw my first Swift at Thorley Wash since 2017 flying with a couple of Swallows. But my mood was deflated again when the lack of general insect life came very much to the fore.

I guess the not insubstantial breeze was partly to blame, but I’ve noticed this year has been extremely disappointing from the point of view of the number of flies and bees around - even worse than in 2024 - although apparently, butterfly numbers nationally have enjoyed a much better year than last year, when most species had a disastrous breeding cycle. But for the time being, I was seeing single butterflies only - the odd Red Admiral, Meadow Brown, Gatekeeper, and even Whites were almost entirely absent. And, until I reached the Reserve proper, no more than half a dozen Banded Demoiselle Damselflies, and only two Brown Hawkers were the only Odonata I was seeing.

Along the path and ‘avenue’ of trees and shrubs leading to the north and south segments of the reserve, I enjoyed a close encounter with a stunning female Southern Hawker - which was ‘hawking’ for prey, flying up and down the path, then occasionally flying up to me (seeming to take a good look) before turning back looking for somewhere to settle on a bramble in the sunshine - which it did, allowing me just the one opportunity to photograph it from a side angle. I had to make do with that. A male Migrant Hawker did the same thing, but no photo was obtained. A few (male) Speckled Wood butterflies spiralled with each other - whilst the odd Small White flitted through.

I continued round until I reached the western edge of the reserve and turned northwards along the ‘path’ (which had only recently been mowed); then I was stopped in my tracks. I don’t have any idea just how I managed to see the Willow Emerald Damselfly (a male) because most people would readily have missed it - resting on a plant (which I couldn’t identify) and almost invisible against its environment. The camera was already poised, so without wasting any time - in case the insect moved off - I took several well composed shots at varying angles - before it was gone and couldn’t be relocated. But I was happy enough, my first Willow Emerald of the year …………….and on ‘My Patch.’

I didn’t see another until I reached the ‘Water Vole’ seat on the north-eastern edge of the reserve, where I rested for 15 minutes for refreshments before continuing southwards along the eastern flank of the reserve - where I saw more several adults and even at least three pairs in tandem, and where once again the camera was busy for a while.

Exiting the reserve and back over the bridge I noticed two Mute Swans on the Stort, swimming northwards, and although I don’t usually take much notice of the species generally (as they are a common sight along the river) the scene presented a fine ‘contre-jour’ opportunity against the bright afternoon sunlight; so, I fired off a few shots accordingly.

I didn’t see any other species of dragonfly until halfway along the towpath northwards - a few Red Darters; at least three Ruddy Darters; more Brown Hawkers (by far the most predominant dragonfly); a few more male and female Banded Demoiselle, and four Emperor Dragonflies were observed. Butterfly species remained scarce with the ‘usual suspects’ only being observed. And then I saw a species of ‘duck’ on the river that completely flummoxed me - at least initially.

But it didn’t take me long to realise that it was a Mandarin Duck, a species I’d only ever seen once before at Thorley Wash in April 2014 when a stunning adult male flew past me in the early morning mist. This new bird appeared to be a juvenile - further observation revealed it to be a male, resting on a broken bough midstream - but it was extremely wary, so I fired off several quick shots before the bird took to the water again, moving swiftly south. I didn’t want to spook it further, so I left it alone.

I have to say that given the overall lack of rain in recent months, the vegetation along the river had massively increased since my last visit at the end of May (health issues and heart surgery prevented me from visiting until today). In particular, the invasive Himalayan Balsam, despite being an attractive plant in its own right, had taken hold along some stretches. Another - though more welcome species - was the Purple Loosestrife, which grew in large clumps along the banks. Rose-Bay Willow Herb was rampant - especially around the Black Poplar plantation on the Essex side - yet it made a pleasant viewpoint from the west bank of the Stort.

So, overall, quite a successful afternoon – the star species being the Willow Emerald Damselflies; the Southern Hawker, and the Mandarin. I was well satisfied. But I paid for it in terms of a swollen right ankle, and a painful right hip. One cannot win all the time it seems.