Along the river valley – The Upper reaches of the River Anton.
The autumn and winter rains have filled the chalk to overflowing and, so, the spring has sprung in this grassy field. Rather than gushing out the water merely oozes from around the roots of the herbs and has dug itself a small river channel just a few centimetres wide. But, it’s a start and, with dozens of other oozes not too distant, they have soon joined up and become a small stream.
In high summer this field is mostly left uncut and, with the stream keeping it moist, the grasses grow lushly and to such a height that rare harvest mice have a home here. I remember the first time I found the minuscule bundles of woven grass amongst the tussocks of cocksfoot (a grass). It was by mistake; I’d lost something, and while searching came upon the first nest. Then, rather like a fisherman challenged by capturing their first fish, I kept looking until I’d encountered two more nests. Of the mice themselves, there was no sign as my size 10 trampling feet had sent them underground yet knowing they were there was quite enough. Nowadays I only look out for their nests in early autumn. By then the nests have served their purpose and both adults and young have dispersed.
Along this watery valley harvest mice are not uncommon, especially in damp meadows. Elsewhere they have suffered severe declines as traditional meadows are trampled and eaten to ground level by the ubiquitous pet horse.
In early March the frogs come to the young river to spawn. It is a mistake to believe the green amphibians only have their early-year matings in ponds. Spawn masses rest on the stream’s margin, out of the main flow and in the narrow drainage ditches that criss-cross the wet margins of the stream. Toads, with their strings of eggs, mostly ignore this location as the water is too shallow for their needs – they seek out the deeper water provided by the gravel diggings further downstream and arrive around four weeks later than the common frogs.
This shallow valley is a patchwork of habitats – meadows, over-grown shrubs, teasels that have long gone to seed and tall trees. The elm trees, who reached, quite successfully, to the sky are long gone. Only their short-term suckers remain, and then only until they are large enough for Dutch Elm Disease to kill them off. Instead, I enjoy the alder trees that cluster along the stream’s edge. Their March catkins hanging down and gently wandering as the breeze takes them. Just as with the hazel the catkins are the pollen producers, the female flowers soon develop into fir cone-like structures that hang onto the branches all year.
Dark and dank come to mind as I view some of the wet woodlands that are occasionally adjacent to the stream. Little sunlight reaches the ground when the deciduous trees are in full leaf and that discourages much ground flora. The humus-rich soil will be oxygen deficient and acidic despite the alkaline rocks a few metres down. Wet, anaerobic and acidic soils are a difficult environment, yet a blackbird is searching around – so something of interest must be available.
And all this encourages me to recall a rhyme; one that conjures up the feel of this place ….
’Twas brillig, and the slithy toves
Did gyre and gimble in the wabe;
All mimsy were the borogoves,
And the mome raths outgrabe.
Watercress beds, unused for forty or more years, but still with artesian boreholes adding water to their flow, allow the incoming stream to spread widely over the gravel bed. This heel disturbing the gravel one can displace myriads of invertebrates – which is why so many wading birds inhabit this patch when little boys and girls are off elsewhere. Watercress straddles the waterway’s fringe, its deep green leaves stand proud of the water, its stems and roots (that harbour myriads of water shrimps) are deeply anchored.
With public ownership of the land, with its growing waterway, is largely left to nature. With a Wildlife Trust managing the site there is a good diversity of cutting patterns in the drier areas. The sometimes-grazed wet meadows grow large marsh orchids with their strap-like, oft-spotted leaves and complex purple flowers. Alongside these flamboyant flowers are the tall clusters of tussock sedges with their needle-ended leaves and brown, insignificant flower clusters. Now the spring chorus of birds is starting – robins, chaffinches, dunnock and many more are singing to proclaim their territories. Of the birds that live here in summer, the grasshopper warbler is the star. Its late evening trills are unforgettable.
The stream’s route now opens out and the water flows into one of several gravels pits that line this gentle valley.
With gravel a few metres deep below the valley, and a town’s suburbs needing building, it is little surprise that the stones have been harvested in the past leaving water-filled lakes. Yellow flag-iris and burr reeds line the fringes, the water itself has yellow waterlilies, and floats of deep green weed and candyfloss algae – a sure sign of an excess of nitrates leached from the local farmland into the waterway. It takes some while for my eyes to start to see the fish, then there appear to be thousands of minnows and sticklebacks in the shallows. Beyond, in the deeper still water, a camouflaged pike hangs motionless. This fish, that can grow to weigh 40Kg, is the top aquatic predator and it keeps a lookout for any unwary fish, young bird or amphibian that crosses its path.
And water birds are present in good numbers. Diving birds, such as coots and tufted ducks, are after deep water weed, insects or fish. Dabbling ducks, like the ubiquitous mallard, consume the surface growing water crowfoot and water starwort. Mute swans and Canada geese frequent this lake too. Skulking in the quieter places I occasionally spot a highly secretive water rail; a bird sometimes called the water hen. It is not a common bird, a relative of the coot, although it is seen here regularly in late winter or early spring as it seeks out insects, snails or unwary minnows on the watery margins.
To see this lake frozen in winter is unlikely. The incoming water is certainly cool, but seldom drops below 6 Celsius, but if freezing conditions do have their effect the water will freeze from the top down – ensuring liquid water fills the lower parts of the lake. Despite the chill, the aquatic wildlife should survive it all.
With large, deep lakes, following the coldest part of the winter, there will be a period when the lake will be around 4 Celsius from top to bottom. When spring arrives the upper layers will warm while the lower parts remain cold. As the summer progresses two distinct layers will develop despite some mixing due to storms, and these distinct zones will continue until the late autumn. The zone between temperature layers is called a thermocline. In a lake such as Windermere, the temperature drop from the surface (around 16 degrees) to 8m is only one degree. From 15 to 60m it holds constantly at 6 degrees.
With this diversity, there are aerial predators here too. Kingfishers take the smaller fish and an occasional passing young osprey keeps the numbers of larger fish down. With fewer shooters aiming at Southern England’s buzzards they now frequent this nature reserve and have, over the last twenty years, been joined by beautiful red kites who skim through the air, twisting their V-shaped tails to change direction, almost never needing to flap their wings to maintain their elevation or speed. Yes, this wet valley is rich in wildlife.
My luck is in today. As I stand, taking a photograph along the river, I spot a buzzard on a fence post. It launches itself and tries to grab something off the surface of the river. Is it a grass snake, or water vole, or frog or fish? I have no idea, especially as it misses! This is a hunting technique I have seen twice in my own garden – then the buzzard was after frogs that were floating motionless in the shallow water.
Grasses and other herbs forming a dense mat over the land fringing both the lake and waterway. So, there is plenty of habitat for terrestrial voles to establish their runs. Here it will be mainly short-tailed voles, as they specialise in thick, deep grassy, open meadows. Their cousins, the long-tailed voles, keep mainly to drier areas. And, where you find voles there will be their nemesis – the kestrel, and possibly the stoat, weasel or fox.
For the next three or four kilometres, the water flows in a four-metre-wide, swiftly flowing river course. The speed ensures not much silt sits on the river bed and that makes it suitable for trout. They sit facing upstream, mouths open to allow the natural flow of water in and over their blood-rich gills absorbing the oxygen from the cool water into their haemoglobin-rich blood.
Being close to the spring line, the water nearly holds the temperature of the underlying cool, chalky rocks throughout the year. Cool water holds more oxygen than warmer water, so the trout are content, especially with the richness of the insect life allowing easy feeding.
In the past, this river’s banks were occupied by water voles. They dwelled in burrows that opened above and below water level. Around the aerial entrances, the grasses were nibbled to a lawn and nearby one could often spot piles of green-black droppings. Now a few water voles are again being found, their relatives having vanished for many years. Why? Firstly, trees began to overshadow the river, reducing light, and so the water weed and herbs needed by the voles. Secondly, it is possible that released, non-native mink ate them out – although I have never spotted one.
With some sections of the river’s surrounds unapproachable, and with wet, unkept woodland adjacent, this is potentially where our local otters breed.
When I researched the otters in the 1970s and 1980s none were to be found here. Pollution from pesticides and aggressive landowners had finished them off. The few that remained in Southern England were still hunted by some of the 11 packs otter hounds and their blood-thirsty human companions. 1978 saw the legal end to otter hunting and, with the Otter Trust captive breeding and releasing the animals, the population started to recover. Now otters are again being recorded along this section of the river, having been absent for many years.
Still swiftly flowing as the water moves down the gradient, the water is beautifully clear. However, the observer sees only a fraction of the life that calls this aquatic system home. To get closer to the life one needs a good net and some basic sorting equipment.
The usual technique to extract the watery life is to place the sweep net downstream and then disturb the upstream gravel. Invertebrates tucked away, out of the current, amongst the gravel, or in the weed, if you investigate there, is washed into the net. By slowly sorting the catch the diversity and abundance of life are exposed.
The river’s food chain starts with the algae that coat the gravel, stones and rocks, and the water buttercup (Ranunculus fluitans) and water starwort (Callitriche verna) that are rooted into the river bed. The sunlight energy, trapped in photosynthesis as sugars and fats, provide food for the vegetation eaters. Amongst the commonest animals encountered here will be immature mayflies, with their three feather-like tail filaments, water shrimp (Gammarus pulex) and water lice (Ascellus aquaticus) – the watery equivalent of the woodlouse. Snails abound and, by searching diligently, even freshwater mussels will be found. Miller’s thumb (or bullhead) and stickleback fish and the uncommon brook lamprey can also be caught. Scarier, there will be plenty of leeches too; they feed off fish blood but this species cannot penetrate human skin.
Water plants are built quite differently than those on land. Water is dense and lifts plants towards the surface. They require little rigidity, so wood is virtually unknown. Just lift a water-living plant – it lacks almost any support. This will change if it becomes emergent. Watercress being moved in a current has a lax structure, once above water it is more rigid.
The leaf design of aquatic plants is also a contrast to their land-living cousins. Their leaves are narrow and strap-like thereby offering less resistance to the current. In still water the leaves may be flat and float on the surface; not so in flowing water.
My river mostly by-passes the local market town’s centre and, at the same time, breaks into the many sub-divisions so characteristic of chalkland rivers. It becomes braided.
Even the smallest of these mini-rivers has its minnows and sticklebacks, so spotting the azure and orange flash of the 30g kingfisher that digs its long nest hole into the river’s bank or even into the soil-holding roots of a fallen willow tree.
The course of the river here has changed over time. In the 1700s, with many roads virtually impassable along the river valleys, canals were dug to allow the transportation of goods. This was true here, with the transport link ending at a wharf in the town. When a railway superseded the local canal, the latter was filled in and the railway line built along virtually the same routeway. Now that to has been closed and a firm human foot and cycle path occupies that footprint, with a braid of the river accompanying it.
Even with houses close by, the walk is rich in birdlife. Friendly male blackbirds, now in their spring finery of bright yellow eye rings and beaks and coal-black plumage, search out worms and other invertebrates almost under one’s feet. Thrushes seek out snails, pied wagtails peck up minute flies, all the while bobbing their tail feathers in that most characteristic way.
Fast flowing waters with rich riverbanks provide a good river habitat. Both can be served sometimes by narrowing the river’s course. To achieve this, faggots, bundles of hazel or willow stalks, are staked adjacent to the bank and bankside vegetation encouraged to grow amongst it. Such a restored bank will potentially be suitable for water voles or even water shrews. The faster-flowing water will keep the clear riverbed and so encourage a healthy population of fish.
Our waterway finally joins up with its parallel sister and enters another gravel digging lake of greater proportions than we’ve yet encountered. It is another nature reserve and a wonderful resource for the local human community.
Cormorants and egrets are common here and their numbers appear to be increasing year by year. Here too the likelihood of spotting a water vole, or even an otter, is good. Occasionally a female otter shows off her cubs by daylight. I have seen one on several occasions in mid-morning with dog walkers and chatting walkers around. One has even been known to approach bankside fishermen for free fish!
Even this early in the year, in the still water, you’ll spot some of the invertebrates that live on the water’s surface. Water is such an exceptional material that it possesses what amounts to a surface film. Some small organisms are so light that they do not break through. They skate over the surface as if it was covered in flexible ice. Pond skaters and Whirligig beetles do this. They skit around capturing even smaller organisms that land on the water.