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Tuesday, June 18, 2024
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NatureWhere there's mud there's birds

Where there’s mud there’s birds

Philip Strange goes searching for avocets on the mudflats around the estuary of the river Exe in East Devon.

As it approaches the sea, the river Exe swells into an impressive estuary about eight miles long and up to a mile wide. The Exe estuary is strongly tidal, a place of ebb and flow where massive amounts of water move back and forth and vast areas of mudflats emerge twice each day as the tide falls. Estuary mud may look uninviting but it is a rich habitat for tiny worms and crustaceans and as rich in biodiversity as a tropical rainforest. Wading birds love this plentiful environment and many species overwinter here and can be seen feeding from the mud. One iconic winter visitor to the Exe is the avocet, a beautiful black and white wading bird.
The town of Topsham on the eastern side of the estuary makes a good gateway for anyone interested in learning more about local bird life on the mudflats. The railway station is easy walking distance from the town and there is plenty to see in Topsham itself. The river has always been an important influence on the town and Topsham was once the second busiest port in England and an important centre for shipbuilding. Times change and nowadays Topsham is a favoured destination for the retired and for tourists alike, its narrow streets packed with enticing cafes, restaurants and gift shops but also cars.
Many fine houses were built here in the 17th and 18th centuries by prosperous merchants when maritime trade through Topsham was in its heyday. These houses can still be seen, seemingly unchanged, along the main streets as they descend to the quay and river. Perhaps the most overtly impressive street is the Strand, running parallel to the river beyond the quay, lined with elegant old houses many built with curved gables in the Dutch style. There was a busy trade with the Netherlands in the 17th/18th centuries exporting woollen cloth made in Exeter mills. Ships returned from Holland carrying Dutch bricks and tiles as ballast which were used to build the houses, inspired by Dutch design.
But what about the mudflats and the birds? If we walk along the Strand until the houses peter out, we reach a raised concrete walkway along the river. This is the Goat Walk and gives good views across the water to the salt marshes and reeds on the west bank of the Exe and downstream towards the river mouth. At high tide, the water comes up to the edge of the walkway but as the tide falls, mud is quickly revealed and wading birds can be seen foraging for food. If you stand here quietly on a winter’s day you may also hear the plaintive, keening call of the curlew echoing across the water.
At the end of the Goat Walk the path turns sharply to the left on to Bowling Green Road with the RSPB (Royal Society for the Protection of Birds) nature reserve appearing in a short distance. This gives access to a viewing platform looking out across the water where the rivers Clyst and Exe merge. As the tide falls, vast swathes of mudflats appear, attracting flocks of waders. The dark mud with its film of water acts as a perfect mirror capturing an image of the sky and clouds above, punctuated by whatever waders choose to feed.
Further down Bowling Green Road is the RSPB Hide which gives unique views across marshy land with small lakes and reed beds at the confluence of the Clyst and Exe rivers. This is the main high tide roosting place for birds on the northern part of the Exe estuary and large numbers of waterfowl and waders may be seen. I once saw a huge flock of godwits grazing here and suddenly taking flight, a breath-taking experience as they wheeled back and forth catching the sun.
In the winter, though, the star species on the mudflats is the avocet a very distinctive black and white, long-legged wader with an extended, slightly upturned beak that it uses for finding food in the mud. The birds arrive on the Exe by November and may be seen on the mudflats off Topsham into February. Sometimes they gather in large flocks feeding not far from the RSPB hide.
Avocets are elegant birds and something about them has captured the local and national imagination. For example, the railway line along the estuary linking Exeter, Topsham and Exmouth is now called the Avocet Line. Beyond Topsham the railway runs close to the river making avocet sightings possible from the train in winter. The Exeter Brewery is another avocet advocate and features the bird in its logo. Perhaps the greatest tribute to the bird, though, was the adoption from 1970 of the bird as the logo of the RSPB, celebrating a major conservation and protection success story.
The avocet was extinct in the UK by 1840 having been driven over the edge by marsh drainage, destroying important habitat, and by hunting and egg collection. The occasional bird still arrived in the UK but was usually shot to satisfy the fashion for stuffed birds as living room ornaments. Paradoxically, a century later, the turmoil of World War 2 opened a window of opportunity for the birds to re-establish in the UK.
With the threat of a German invasion, the low-lying Suffolk coast was considered particularly vulnerable. Various physical defences were erected on beaches but another strategy included the deliberate flooding of coastal marshland around the Minsmere river to hamper invading forces. After the war, the water was allowed to recede creating a mosaic of shallow pools and reedbeds, a haven for wildlife. In 1947, the RSPB took over managing the site and in the same year seven pairs of avocets nested on the Minsmere reserve. The birds were guarded carefully and by 1949, after some ups and downs, 40 young avocets fledged. This is one of the most successful conservation and protection stories and nowadays, avocets breed along the East coast of the UK in good numbers each summer.
In winter, many migrant avocets arrive in the UK especially in the south west. Several hundred birds overwinter on the Exe estuary each year and even greater numbers may be seen around Poole Harbour. The birds come for the milder weather and for the mudflats with their rich biodiversity and the well-stocked winter larder they provide for these migrants.

Philip Strange is Emeritus Professor of Pharmacology at the University of Reading. He writes about science and about nature with a particular focus on how science fits in to society. His work may be read at http://philipstrange.wordpress.com/

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