Five-mile nature walk taking in Thorley Wash and Rushy Mead reserves and the Stort Navigation around Bishop's Stortford

Nature Notes columnist Jono Forgham covers your fortnightly look at nature around Bishop's Stortford…

After the washout that was Easter Monday, I set off the following day with a cloudless sky overhead, great light and potential for the temperature to rise to a pleasing degree. I parked in Spellbrook Lane East and picked up the towpath of the Stort Navigation by the lock gates and headed north.

As I accessed the path a song thrush burst into full song, a melodic warble with favourite passages often being repeated three times before the bird (a male, as in most instances only male birds sing) moves on to a new passage of highly complicated notes. Fortunately the bird was out in the open, offering great photo opportunities, before I headed along the towpath towards Thorley Wash nature reserve.

Bird song was apparent constantly throughout the whole five-mile walk, so my bird list, which totalled 38 species, included several that I only heard and did not actually see.

Great tits and blue tits flitted around near the red brick footbridge, a green woodpecker "yaffled" in the distance and wood pigeons were ubiquitous as were chiffchaffs with their easy-to-identify "zip zap" or "chiff chaff" song. All very repetitive, but it certainly carries a long way and does help to pinpoint the small bird as it moves through the upper branches of trees, usually those that are already showing leaf emergence as that is where the insects will be found.

I crossed the bridge and completed a full circuit of the reserve. Several smart sculptures on the path here with one being a particularly striking dragonfly. Too chilly at this time for butterflies to be on the wing, but my plan was to walk as far as Rushy Mead reserve before returning along the towpath when, hopefully, the temperature would have risen and encouraged insects onto the wing.

The path around the reserve gives good views of the willows that grow in the centre. A blackbird was sat atop one in full voice whilst the distinct call of a reed bunting came from another. Overhead, a party of herring gulls headed west, but views over the reserve didn't give too many other sightings so over the footbridge and I continued along the towpath towards Pig Lane.

I had hoped to encounter some recently-arrived migrants from sub-Saharan Africa and a singing blackcap made me think it was going to be my day, but, alas, apart from the chiffchaffs, this was one of only two summer species I came across.

This area is an important habitat for overwintering birds with snipe found on the reserve, little grebe on the river, siskins in the alder trees and water rail often in the deep wetland vegetation. These, however, will have all departed to their breeding grounds.

I stopped to chat with a dog walker who knew me from these articles and the Stortford Nature Facebook page. As we chatted, a cormorant flew by, a noisy jay alighted in a tree on the opposite bank and a great spotted woodpecker called from near the railway line. All along this stretch to Twyford lock gates mallards and moorhens busied themselves on the water, feeding and showing signs of courtship.

I arrived at Pig Lane and took a break on the bench by the lock gates. A grey wagtail called from somewhere, but I couldn't find him. Coots and moorhens here gave more photo opportunities, both members of the rail family but easily identified by the white beak on the coot compared to the red and yellow bill on the smaller moorhen.

By the exit gate at Pig Lane I noted a selection of wild flowers in full bloom. Over the fence, an impressive stand of brilliant yellow marsh marigolds whilst, at the side of the path, several cowslips nodded in the breeze. Also along this part were both red dead-nettle and white dead-nettle.

Along the towpath, a pair of Canada geese fed on the vegetation before slipping into the river as I approached, grumbling to themselves under their breath.

I arrived at Rushy Mead reserve and, upon entry, I was faced with a large stand of nettles. Always worthy of a thorough search. I changed to my close-up macro lens, got down on all fours and had a good rummage around. Pleased I did as I came across several Bombylius major, the amazing dark-edged bee fly, and a smaller fly species, Melinda viridicyanea. Good to eventually get a few insects into this article after a dearth throughout the winter.

The bee fly is an amazing insect. With a long proboscis, which looks dangerous but is no more than a straw for drinking nectar, the females fly over the holes in the ground of solitary bee species as well as larger bumblebee species and flick their eggs with their wings onto the ground, adjacent to the hole. The grub hatches and crawls into the bee nest where it feeds upon the comb and the bee larvae. On a warm afternoon in mid-April they can be found in profusion, showing just how successful their breeding cycle must be.

A wren popped up for a photo and the first butterfly, a peacock, zipped by. I made a note of the grid reference as I am recording all local butterfly sightings this year. More about this scheme in a future article. Overhead, four common buzzards mewed and circled menacingly.

I began to retrace my steps back along the towpath, the sun now higher in the sky so still helping with photos. A cormorant, in full breeding plumage, posed on top of a tree at the lock gates and goldfinches argued from the nearby hedge.

I then found myself checking the far bank's vegetation as plenty of bird movement was apparent. Long-tailed tits and my second summer arrival, a willow warbler, singing from deep inside a willow. Its song is a descending, flutey call and helps identify this bird from the virtually identical chiffchaff. Without the call, the only surefire method to correctly identify these two species is to make a good study of the wings when they are folded back. This can prove tricky as both species rarely stay still for long.

I returned to stand on the footbridge. The breeze was picking up a tad, but this didn't discourage another peacock butterfly from passing overhead and, some distance away, a male orange-tip butterfly darted for cover. Another willow warbler called at the same time as the resident Cetti's warbler burst into its very loud and explosive song. A skulking bird of deep vegetation, invariably near water, it is often heard but seldom seen. This one gave a brief view as it popped up onto a bramble bush before immediately returning to the dense cover below. I waited a while, hoping to get a photo of this brown and grey species, but it wasn't having any of it so I wandered back.

In the damp area on the left as the walker heads to Spellbrook Lane was a family party of mallards. At least six ducklings skimmed the water. They couldn't have been more than 48 hours old and were soon lost to view in the mass of tree branches that grow over this swampy patch. Probably a fairly safe place to bring these youngsters up as it's very difficult for many predators to get into the area, apart from weasels and rats.

I arrived back at the lock gates to note that the song thrush had moved to another favoured song post and was still singing brilliantly. I checked my notes to see that, even though I had seen/heard 38 species, the only bird of prey I had observed had been the common buzzards. Not often I conclude a five-mile local wander without seeing at least a red kite, if not a kestrel.

Over the next six to eight weeks this habitat will become full of wildlife. More migrants will arrive, perhaps even a cuckoo will be heard calling and plenty of dragonflies and damselflies will emerge as well as mayflies and St Mark's flies, the irritating ones with long dangling legs that fly at face height along footpaths near hawthorn bushes and hedges. So called because they fly around about April 25, St Mark's Day. This date is also the day I plan to carry out my next Nature Notes wander, so I shall look out for these flies.

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