Tales of the Riverbank

Colin Varndell brings us, in words and stunning pictures, just some of the animal and plant life to be found along Dorset's rivers at this time of year.September 2008

Colin Varndell brings us, in words and stunning pictures, just some of the animal and plant life to be found along Dorset's rivers at this time of year.

I had been sitting quietly in the shade of a hawthorn on the bank of the Mangerton river near Bradpole when I heard the piercing, piping call of a kingfisher. The bird appeared from upstream, banking sharply as it came round a bend in the river and alighted on a fencepost about 15etres from me. I froze, hoping not to be noticed. The kingfisher fixed its intense stare into the pool beneath and within seconds splashed headfirst into the water, returning to the post with a stickleback.

The bird held the fish by the tail and flicked it onto the post several times presumably to kill or at least stun it. The fish was swallowed head first just as another piping call came from around the bend. As the second kingfisher darted past, the first bird took to the air and chased it downstream. I watched them disappear to the sound of their excited calls.

The kingfisher in Dorset is an easy bird to observe as it is so predictable. It habitually flies only inches above the water surface; it regularly uses favourite perches and patrols its territory constantly all through the year. You would need to sit only for 20 minutes or so on the bank of any of Dorset's unpolluted rivers and you will see one.

Dorset's rivers are teeming with life, ranging from the tiniest insects to large aquatic mammals and birds. The food chain begins with the lowliest of invertebrates, the aquatic nymphs and larvae. Many species of flying insect actually begin their lives in fresh water, mayflies, dragonflies, mosquitos and stoneflies, for example. At the aquatic stage they may feed on smaller creatures or, in turn, be food themselves for fish or other predators.

On Dorset's rivers the most beautiful of these insects are arguably the demoiselles, two species of damselfly which live near water where they both lay their eggs on floating vegetation. These insects have evolved to take advantage of two completely different habitats - under water where they can live for up to three years, and in the air where they prey upon gnats and midges in flight. The beautiful demoiselle is found on quicker-moving streams and rivers in the south and west of the county, while its close relative the banded demoiselle favours Dorset's larger, slower waterways like the Frome and the Stour.

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The riverbanks are home to many specialist plants which like to grow near water like yellow flag, great willowherb, meadowsweet, purple loosestrife, water forget-me-not, mimulus and water mint to name just a few. However, the fortunes of these wild plants are changing rapidly by the spread of the non-native Indian balsam which was introduced into southern England from the Himalayas. This is a vigorous plant with large leaves that block out the light for smaller, native species. Its spread across Dorset has been swift and it is now seen in huge drifts crowding the banks of many rivers and streams.

Another introduced wild flower to be seen along Dorset's rivers is in fact the largest wild flower in the county - giant hogweed which can grow up to three-and-a-half metres in height with flower heads measuring 45 centimetres across. This enormous flower should not be touched with bare hands as it causes severe skin irritations. It can be seen along the River Brit near Beaminster and also along the Allen in the north of the county. Wherever there is unpolluted water there are fish which attract predators of both avian and mammal kind. The North American mink has been the scourge of many of Dorset's rivers after they escaped from fur farms in the 70s. The mink is an aquatic predator and is just as eager to kill mammals or birds as it is to devastate fish populations. Certainly, the mink has been responsible for the drastic decline in water-vole populations across Dorset.

However, there is an antidote on the horizon in the form of returning otters to Dorset's rivers. The otter and mink do not coexist happily and the larger, more powerful otter will dominate in any river territory. The otter is difficult to observe as it tends to be mainly nocturnal, but there is growing evidence of its presence, especially in the west of the county. Hopefully, if the otter continues to expand its range we will see less mink and more water voles again.

The grey heron is a natural predator of life in Dorset's rivers, and you are just as likely to encounter one stalking prey in a small stream as you are in the margins of our larger waters. The heron is highly adaptable and can catch insects and amphibians as well as fish.

A close relative of the heron, and a relative newcomer to Dorset's rivers, is the little egret. In the past it was an unusual occasional visitor but it has bred in Dorset for over 10 years now and it is thought that the little-egret population actually outnumbers the herons.

In the west of the county, where rivers tend to run much faster on account of the more undulating landscape, the dipper can be seen. This slighter smaller-than-a-blackbird-sized bird has dark-brown plumage and wears a distinct white bib. It gets its name from its habit of bobbing up and down when standing on a favourite stone in the river. The dipper is capable of finding food under water and frequently ventures under the surface in pursuit of caddis-fly larvae and other invertebrates.

Where there are dippers there are usually also grey wagtails because the habitat suits both birds exactly. The grey wagtail is often wrongly referred to as the yellow wagtail on account of its predominant yellow colour. However, it is the grey head which gives the bird its name. Grey wagtails are extremely vocal in spring and summer, standing on rocks or other perches with their long tails constantly wagging.

It may well be that as humans we have romantic ideas of riverbank life akin to The Wind in the Willows, and there is something very magical about a stroll along one of Dorset's rivers on a summer evening. But for the creatures which live there, this habitat is little short of a battle zone, as the water which attracts so many fascinating creatures is also a magnet for their enemies.

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