Thorley Wash

THORLEY WASH - MY LOCAL PATCH David Sampson

I first became aware of the area around Thorley Wash in the late 1990’s when I came over to Bishop’s Stortford to visit my sister, who lived there. I was invariably persuaded to accompany her along the Stort Navigation in the course of taking her two dogs for their daily walk, although I was always more interested in the riverine environment and particularly the wildlife.

Of course in those days the walk along the Stort Navigation was virtually unrecognisable from the way it looks today (in 2015), mainly I think because there were noticeably more trees and shrubs then; in particular Thorley Wash was mainly known as a Flood Plain, with a large expanse of Willow and similar scrub, but with no proper access around the reserve as such. I seem to recall seeing a fence around both north and south sectors, and I was vaguely aware that it had SSSI status, although I didn’t know why. To my knowledge no grazing took place here until Asian Buffalo were introduced three years ago, and latterly Highland Cattle in 2014; but that was after the area was allocated reserve status.

In addition the route through Spellbrook to Hallingbury was similarly overgrown with Willow scrub, and I was always aware that it was potentially an excellent habitat for birds too. And what’s more, a really beautiful environment to boot. This area too has been largely transformed (not always in my view necessarily in a wholly positive way) with Konic ponies being introduced in recent years.

In June of 2002 my father and I made the decision to move to Bishop’s Stortford, and from that moments on, once we’d settled in, I was in my element nature-wise because the riverine environment was something that was almost completely new to me, compared to the largely wooded and agricultural environment I knew back in Harold Hill, Romford (as excellent as that was). I joined the Bishop’s Stortford Natural History Society quite quickly, and almost immediately joined the Bishop’s Stortford Bird Group. I was really looking forward to discovering a completely new birding environment.

For recording purposes, the area I call Thorley Wash covers the entire length of the Stort Navigation from Twyford Lock in the north southwards as far as Spellbrook. The eastern bank of the Stort Navigation is in Essex, whilst the western bank is in Hertfordshire. Part of the immediate hinterland is included, so some records over the years fall in both counties. Thorley Wash - now managed as a Reserve by the Herts and Middlesex Wildlife Trust, does not (thankfully) impinge into Essex, although - again for recording purposes - I do tend to included sightings from the Walbury Estate which immediately flanks the Navigation channel to the east, as well as the rough grassland/scrub and the Poplar plantations running northwards. The actual River Stort itself only follows part of the navigation channel, being in effect no more than a backwater around Thorley Wash until it rejoins the navigation south of Spellbrook.

I have it on reasonably good authority that before I came to Stortford, not many bird watchers submitted bird sightings from Thorley Wash (though obviously there were a few stalwarts who did). But it did always seem strange to me that once I began submitting records, more and more local birdwatchers found their way down to Thorley Wash, and as a consequence the level of recording, as well as the number of species seen, began to improve. So maybe I can feel justifiably proud that I’ve done my bit to promote the area.

The first really good bird I discovered on the area known now as Thorley Wash Reserve, was a Jack Snipe (viewable mainly from the Navigation channel) on 7 December 2003, with a flyover flock of Golden Plover on 19 December 2003. To my knowledge neither record has been repeated (although I understand that a singleton Jack Snipe was recorded there early in 2014 by another recorder). My first Woodcock was recorded on 20 January 2009 and (somewhat surprisingly) my first Green Sandpiper on 19 January 2013. Water Rail is present and breeds - but is exceptionally shy, so is difficult to observe most of the time; so actual numbers are hard to predict. Other notables include Mandarin (a drake flypast) on 23 April 2014; Shoveler - a female, followed by a drake in January 2014; Pochard 30 December 2010; Teal and Gadwall also occur almost annually these

days. Little Grebe no longer breeds, but most years there is a winter build-up between Spellbrook and Twyford Lock which has peaked at 15 individual birds.

My first Little Egret was on 16 May 2012 (although I’ve since recorded three together near Twyford Lock in January 2015); my only Merlin was on 12 January 2004; my first Hobby 2 September 2005; a Peregrine was observed on 3 November 2013, and my only Red Kite on 13 May 2012 (although I did record another slightly south of Spellbrook on 20 April 2009). Common Buzzards occur regularly, and I have seen up to six individuals in the air at the same time; just one pair is known to have bred locally. Common Kestrel is present as a breeding species with one pair on the reserve and another on the periphery. Sparrowhawk occurs regularly as singleton adult birds, with probably just the one pair breeding in the vicinity.

I have had two sightings on Long-eared Owl, one distant record being mobbed by Magpies and a Barn Owl on 8 February 2007, and an absolutely magical encounter with Stephen Patmore on 20 April 2009 - which will always live in our memories, because of the closeness and longevity (possibly 5 minutes or so) of the sighting. I have had just one record of a Little Owl (seen on several consecutive days roosting in trees opposite the reserve in January 2007), and one of a Tawny Owl on 14 May 2004 (which was a heard only record). I’ve had several Barn Owl sightings since my first on 3 April 2006.

In recent years (with a noticeable 4 years gap previously) pair of Lesser Spotted Woodpeckers was present and may have bred near Twyford Lock (in 2014 once the news of their presence broke, many people came to observe them, and as a consequence maybe the reserve itself received more publicity). Both Green Woodpeckers and Great Spotted Woodpeckers are common, as are Common Whitethroat; Garden Warbler, and Blackcap, but Lesser Whitethroat has not bred here for several years. Only one pair of Eurasian Reed Warblers breeds annually, with Sedge Warbler restricted to 4-5 pairs. Willow Warblers have drastically reduced in numbers with probably 4-5 pairs breeding. Chiffchaff has similarly declined as a breeding species, with probably less than 10 pairs. In May 2014 up to four singing male Grasshopper Warblers were present on the reserve, but possibly only two pairs actually bred. Marsh Tit no longer occurs, but there is a healthy population of Blue and Great Tits, and Long-tailed Tits occur regularly, with one or two pairs breeding. Nuthatch and Treecreeper still occur, but are diminishing as a breeding species. Bullfinch too occurs occasionally. There are probably 2-3 pairs of Kingfisher along the Stort Navigation, and are known to breed along the backwaters. Stonechat and Whinchat still occur, but are becoming less common as a vagrant visitor. Regrettably, Spotted Flycatcher (which was likely to have bred in the Walbury Estate up to 2010) has been largely absent, even as an autumn vagrant. Reed Buntings gather in small winter roosts of up to 20 or so individuals, and in summer probably up to 4-5 pairs breed.

Of course, there are other bird species too which have been observed here over the years including Cuckoo; Lesser Redpoll; Brambling and a good number of the more common passerine species. To date the species list stands at 107, though hopefully it will expand gradually in the future.

Since the reserve has been managed, the number of Dragonflies has increased dramatically. The rarest in recent years has been a small number of Hairy Dragonfly, with up to two females observed in the process of ovipositing their eggs in early May. Broad Bodied Chaser; Four Spot Chaser; Southern Hawker; Brown Hawker; Migrant Hawker and Emperor Dragonfly all occur regularly. Banded Demoiselle; Common Blue; Azure Blue; Blue-tailed; Large Red and Red-Eyed Damselfly are all relatively common.

Butterflies too, are reasonably well represented. Brimstone; Peacock; Small Tortoiseshell; Red Admiral; Painted Lady (though much less so these days); Comma; Speckled Wood; Common Blue; Brown Argus (up to 3 pairs in 2014); Clouded Yellow (in August 2013 good numbers were observed on the reserve following an influx from the Continent); Large White; Small White; Green-veined White; Orange Tip; Holly Blue; Small Copper; Large Skipper; both Small and Essex Skipper, though the latter has reduced dramatically in recent years; Meadow Brown; Gatekeeper and Ringlet.

Mammals have always been less obvious. Fallow Deer and Reeve’s Muntjac have been recorded; Red Fox is relatively common; Badger I know occur although I’ve not actually observed them personally; Weasel and Stoat do occur but are irregular. Mink has largely been eradicated, but may still occur; Common Shrew and Water Shrew are known to occur. Field Vole remains relatively common; Water Vole has been recorded (I observed an individual swimming across the Navigation in January 2010, as it was in turn being observed by a pair of Weasels on the north bank; but that is my only record of the species, although it was not ratified by the powers that be). Otter has so far eluded me. Rabbits are prolific, but I’ve yet to record Hare in the surrounding fields.

Of the reptile species, I have only recorded Common Frog; Common Toad; Grass Snake; Slow Worm, and Common Lizard.

The reserve was purchased and is managed by the Herts and Middlesex Wildlife Trust in 2011, with major work being undertaken late 2012 into 2013 to clear the extensive Willow scrub. It was opened to the public in May 2013, with an access track all the way around the north section, and another partially along the south section. The area was granted SSSI status in 1986, mainly for it’s plantlife, and the presence of Dermoulin’s Whorl Snail, which apparently remains to this day. Personally, I would have preferred the Trust to have introduced a small scrape, although to be fair an area of standing water does exist to this day at the north end of the northern section, and attracts several species of duck and waders such as Common Snipe and Green Sandpiper.

In the summer of 2013 up to 12 Asian Buffalo were introduced, and these were relatively successful in keeping the vegetation to manageable levels. In the summer of 2013 up to six Highland Cattle were introduced (replacing the buffalo) and this was seen as a very successful move. I understand the Wildlife Trust hopes to maintain the Highlands in future years.

In June 2015, about 160 Water Voles were released on Thorley Wash as part of a reintroduction programme undertaken jointly by Herts and Middlesex Wildlife Trust and the Essex Wildlife Trust, and this is currently ongoing.