HABITATS

by Duncan Fraser, Eastwatch guesthouse, Spittal.

Duncan studied behavioural ecology and evolutionary biology at the University of Edinburgh and spent most of his previous career in scientific and technical publishing. 

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A string of pearls

Berwick U3A’s Tweed and Coast Nature Trail offers either a rich diversity of habitats - or one, depending on your perspective. You can view it as a series of small individual pockets of unique habitat, strung along the Tweed like pearls on a string. Alternatively, see it as a single gem, which when viewed as a whole represents how humans, animals, plants, buildings, land, river and sea have interacted throughout time and do so today. 

 

How you approach it is up to you, but it’s rewarding to take the time to examine each ‘pearl’ individually while stepping back at each one to think about its overall ecological context. Some pearls will crop up more than once - gardens, for example, appear here and there along the route - whereas others, such as the river, are always present.

 

Another persistent feature, though much less welcome, is litter. Aside from being a messy annoyance, litter can trap small animals, block sunlight from plants below, and as it degrades release polluting chemicals into the soil and water. Plastic waste is a major concern all along the walk. It’s worth pointing out that one species that we lack from this area is the poop bag fairy. So, please bring your dog on the walk and make sure you dispose of any dog poop responsibly.

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What are the pearls?

• Parks and gardens: characterized by diverse vegetation, introduced non-native species, human-cultivated varieties, and intensive human management

• Grass and pasture: less intensive management but the effects of grazing animals are significant

• River, banks, and estuary: significantly impacted by water and salt levels daily (tides) and seasonally (droughts and floods)

• Woods: mature trees of mixed native/non-native species, generally on steep slopes, in narrow ribbons running parallel to the river

• Buildings and bridges: Berwick’s answer to artificial cliffs 

• Industrial quayside: where human impact is at its greatest on a day-to-day basis

• Dunes and beach: winds, tides, people, dogs, campfires, picnics all play a part in shaping Spittal point and beach. Not to mention the tides...

• Cliffs: topped with grazing pasture, the last leg looks back over Tweedmouth and Berwick and the trail both literally and figuratively by recalling the pasture at the very beginning

 

Parks and gardens

The Tweed and Coast Nature Trail starts in Coronation Park. A large variety of ornamental foliage plants, flowers, and trees provide a wealth of opportunities for pollinating and nectar-feeding insects and their predators: other insects, birds, domestic pets, and wild mammals. At the same time, overcutting of grassy lawns can leave a desert for invertebrate life in the middle of often spectacular floral displays. Parks and gardens are therefore an interesting habitat to think about: they both give and take from the natural world.

 

As you make your way through Coronation Park, try to identify native/non-native varieties of plants and look closely for the insects using them. Which flowers are most popular with bees in the summer? Which trees or fruits are fed on by birds in the autumn or winter? Look out for areas where grass has been cut short and get down on your knees for a closer look. Do the same with unmown areas. Can you spot a difference in insect life? 

 

Similarly, are there corners that have been left to run wild or, even better, been piled with dead vegetation? Check these out for animal life and think about the role these rotting piles of vegetation have as rich refuges for animal and insect life. 

 

Look upwards to neighbouring trees and on the ground to identify bird species that use the park and check out neighbouring gardens for cats. Does the park provide a feeding ground for birds, for cats or for both? 

 

Grassland and pasture

The unmanaged grassy slopes from the River Tweed up to the ruins of the curtain wall of Berwick Castle facing, across the footpath, the scrubby mixed pasture could arguably be the ecological highlight of the walk. These areas are far from natural but together they represent the least managed sections of the trail.

 

Grass left unmown, with limited human interference, provides a rich environment of invertebrates and for the birds and animals that prey on them. Sheltered by long growing stems and leaves, the moist lower levels are full of herbivorous worms and beetles but also carnivorous animals like centipedes. You’ll be very lucky to spot insectivorous mammals here, as they are generally shy, but they’ll be there, as will domestic cats. Take your time here, pause,  and your patience might be rewarded.

 

The scrubby pasture opposite is one of the richest habitats on the Tweed and Coast Nature Trail. Thorny clumps of small trees and shrubs provide shelter for birds and small animals, as well as pollen, nectar and fruit depending on the time of year. They also protect tree saplings from larger grazing animals and can be thought of as nurseries for larger trees.

 

The grazed areas of this pasture are a near-perfect illustration of a mini ecosystem in action. Grass, via photosynthesis, uses sunlight to convert water from the soil and CO2 from the air into sugars and then uses these, together with soil nutrients, to fuel its growth; cows and sheep graze on this grass, and swallow it into four-chambered stomachs where it is fermented by gut bacteria which use it to multiply and grow; grazers then digest the microbes to provide energy and nutrients for themselves, and the waste products are deposited back on the ground as dung which is acted on by decomposers (soil microbes, fungi, and invertebrates) to add nutrients back into the soil to grow more grass, and so on.

 

Think about this the next time you pass grazing cows and sheep and consider what that pasture might look like without them.

 

River, riverbank and estuary

This is the largest habitat in the whole of the Tweed and Coast Nature Trail: powered by changing water and salt levels, the challenges and opportunities for wildlife here are large if they have evolved to cope. If you have the time do this section of the walk twice, at low and high tides and take notes of the differences.

 

The Tweed itself is always in motion flowing downstream towards the sea from the Scottish Borders carrying suspended soil and silt nutrients - but twice a day, the river flows upstream from the sea when the tide is coming in. This reduces the Tweed’s ability to carry its suspended load and so mud, silt and sand start to build up where currents are slower. This is a rich food source for plants and invertebrates. If you are visiting at low tide, see if you can spot some at the edge of shallow water remembering to stay safe. You certainly won’t be able to miss seaweed and grass coming into close contact - perfectly illustrating where wildlife on land meets wildlife in water. It’s this variety in species that has played a part in creating a fantastic environment for our colony of mute swans.

 

As you leave Coronation Park the greener banks provide homes for salt-tolerant plant species and insects, solid ground for birds like ducks and herons, and also for mammals. You might be lucky enough to spot otters around the Royal Border Bridge. Otters are a sign that the river ecosystem is in fairly good health. Further downriver as you approach the sea you can spot seals in the water or even lounging on sandbanks protruding from the river at low tide. 

 

There is plenty to see here on river and around it so take your time and look around.

 

Woods

There are two sections where woodland plays a role in the overall ecology of the Tweed and Coast Nature Trail: on the left, between the Royal Border Bridge and the Royal Tweed Bridge, and on the right along Dock Road.

 

Both areas are longer than they are wide, and are surrounded by built-up areas. A mix of native and non-native species and being threaded through with public footpaths, they don’t provide the sort of habitat that you normally think of when you imagine a wood. However, they are a refuge for invertebrates and birds including more typically rural species like crows and wood pigeons. Both are easy to spot and can make for entertaining viewing if you pause and just watch, especially the crows playing in the air currents on a windy day.

 

Buildings and bridges

There are buildings all along the Tweed and Coast Nature Trail, from Coronation Park at the beginning to the houses along Spittal Promenade near the end. As with most human activity, the interactions of buildings with the natural world are both positive and negative.

 

Buildings provide shelter from the winds and shade from the sun. They provide height and therefore relative safety for nesting birds or vantage points for feeding opportunities. Stone or concrete is used is a substrate for mosses and lichens, and cracks in mortar are rooting sites for more complex plants. Keep an eye out for high-level greenery on gutters, chimney stacks, and walls. Stone warms up more quickly than air when exposed to sunlight so when (if?) the sun is out, and especially in the warmer months, look out for insects, especially butterflies and bees, basking in the sun to warm up. Residential buildings are often surrounded by gardens so refer back to the earlier section.

 

As you walk the Tweed and Coast Nature Trail you can’t miss the bridges. First, The Royal Border Bridge soars overhead, followed by the Royal Tweed Bridge, and then Berwick Old Bridge. All three provide relative height, warmth and sheltered spots for the animals and birds able to take advantage of them. Take the time to examine them from top to bottom. Look for birds and insects higher up but also look at the feet of the bridges in the water and the eddies and vortices these create in the flow of the Tweed downstream and the tide upstream. How might these affect water birds, fish, and small aquatic animals? The bases of the bridges also create opportunities for shallow water-loving plants where the greater river depth might otherwise have prevented them from taking hold. Notice, just above the water, launch pads for ducks, cormorants, and gulls. 

 

Industrial quayside

At the halfway point of the Tweed and Coast Nature Trail we have the quaysides of Berwick and Tweedmouth and the mooring spots along Dock Road. Human activity on the river is a significant factor affecting animal and plant life here. It’s worth noting, however, that there has been human activity on this stretch of the River Tweed for thousands of years and the levels seen today are dwarfed by heavier use made of the river in the past.

 

The intensity of human activity is one thing that affects wildlife but so is the type of activity. Noise levels from engines, exhaust fumes and discharge from boats are all potential sources of pollution. However, river flow and the tides will help mitigate some of this. 

 

What do you think? Have a look at the river and the buildings around it. You will see, of course, gulls and the second-largest moulting colony of mute swans in the United Kingdom. You will also see species of duck, mainly mallard but also the predatory goosanders, and herons are frequent visitors. The presence of predatory birds shows that there is food in the river here, which is encouraging. If you are lucky you might catch a ripple on the surface or a flash of silver and a splash of a salmon, or the curious head of a seal. 

 

As river use changes and more people use the river for fun including kayaking, boating and jet skiing, it is becoming increasingly difficult to maintain a healthy balance between nature and humans and it’s a conversation that we should all remain engaged in.

 

Dunes and beach

As you near the end of the Tweed and Coast Trail at Spittal Point, nature takes a shift in tone from town and river to a more instantly recognisable coast. Sand dominates and is constantly on the move due to the tides and wind. It’s here, too, that the Tweed takes a sharp left, followed by a right turn, and then empties into the sea at the end of the pier. Constant change on land and in the water is the main factor here. 

 

Grasses, primarily marram, on the dune section near the yacht club help stabilise the sand and in turn provide a habitat for small birds and a hunting ground for cats but it’s further down the beach and just offshore, between the high and low watermarks, where you will see the most life. 

 

Seaweed washed ashore provides nutrients for insects and invertebrates and in winter can be piled fairly high.  It is worth putting on a pair of gloves and having a dig around to see what you can find. The sand itself can seem alive sometimes with amphipods, also known as sandhoppers or sand fleas (although these ones don’t bite), leaping out of your way. If you stop and listen quietly you can hear them jumping. Tell-tale piles of sand further down the beach, or tiny holes blowing bubbles when the waves wash over them, show where marine worms are digging their tunnel homes. These worms provide food for wading birds like dunlin which can also be seen. Just off the coast in the summer months you will also see terns and gannets diving for fish and if you do, keep an eye out for seals and Berwick’s famous bottlenose dolphins.

 

By now it’s inevitable that you will have spotted some plastic waste washed ashore. Pollution of our seas by plastic is a well-known global problem. Plastic causes many problems for all marine life, too many to list here, but take time to  consider the impact on Berwick’s flagship animal species of swans, seals, salmon and dolphins. If you have time, consider doing a quick litter pick: even one fewer item of plastic litter in our environment helps.

 

Cliffs

The Tweed and Coast Nature Trail comes to an end high up on Spittal cliffs. The cliffs are topped with pasture that is used to graze cattle and now we are almost back where we started.

 

Unlike the cliffs on the Berwickshire coast around St Abbs you won't find many nesting seabirds on these cliffs, unfortunately. They are sufficiently steep to stop cows straying downhill but not totally vertical - check out the rocks sticking out of the sea just offshore, note the angles and imagine how that extends into the cliffs themselves. Are they steep enough to prevent predators from raiding nests for eggs and chicks? The lack of nesting birds suggests that they are not. 

 

What you will find, however, are cattle and rabbits grazing the grass down to a low velvet covering and also if you are here at the right time of year pockets of wild orchids and other flowers providing food for pollinating insects.