The March of Biodiversity progress at Dun Coillich.
When the 1100 acres of hill land that is called Dun Coillich was bought by the Highland Perthshire Communities Land Trust in 2002 it had been used as a deer park. The fences, which were in any case in disrepair, had been designed to keep deer in and not to keep deer out. HPCLT’s biodiversity plan was to create a mosaic of habitats, which would involve about one third of the land being woodland.
At the time of purchase the only trees were ones clinging to inaccessible rocky areas such as the Allt Mor gorge. HPCLT obtained forestry grants and an interest-free loan from Harry Potter author, J.K.Rowling to allow them to purchase and plant a variety of native trees. Trees were also allowed to regenerate naturally in many areas.
The native trees planted included - Oak, Silver Birch, Downy Birch, Hazel, Wych Elm, Holly, Rowan, Juniper, Aspen, Hawthorn, Ash, Elder, Alder, Scots Pine, Grey Willow, Crab (Wild) Apple.
The Goulandie Burn which runs close to the main car park at Dun Coillich was used to fill shallow scrapes (small ponds), which were created using a mechanical digger. The idea here was to create a habitat for water birds and amphibia. Waders such as Curlews and Oystercatchers have benefited and a smaller species, the Reed Bunting has moved in. When the surrounding trees have grown a little more we can expect Sedge Warblers. The nearby Goulandie burn has sandy banks and here there is a colony of Sand Martins. There are also dippers on the burn. The scrapes need active management to prevent them being clogged by Reed Mace and silting up. Excess vegetation has been removed and leaky dams establish - all under the guidance of Dragonfly expert, Ruary Mackenzie Dodds of the British Dragonfly Society. One spectacular large species of Dragonfly is the Golden Ringed Dragonfly, which as the name implies has golden rings down its abdomen. The female lays its eggs, not in the water, but in damp mud alongside the water. As with other Dragonflies, it has a predatory larva (nymph) with mouthparts that can spring forwards to catch tadpoles, caddisfly larvae and sometimes tiny fish.
It was some time before the Trust was able to repair or replace the fences to make Dùn Coillich largely ‘deer and sheep proof’. Once this was done the one quarter of a million trees that had been planted and the natural regeneration took off. When we compare the developing woodlands of Dùn Coillich with the, still largely treeless, land beyond its boundaries there is a big contrast.
As trees grow there is a progressive change in the habitat and the biodiversity changes too inevitably reflect these changes. We have seen new species of bird arrive and certain species increase in number. The scrub-height saplings are attractive to Whitethroats and Whinchats and both these species are now breeding in large numbers.
Dùn Coillich is host to a Blackcock Lek (an area of flat ground where male Black Grouse dance to attract females, called Grey Hens. The Black Grouse prefer a woodland edge habitat and so the developing trees suit them well, but habitat management will be needed to ensure that their lekking areas remains clear of trees.
Dùn Coillich has a small mature plantation of Scot’s pine that was there before 2002 and this is a habitat for Great Spotted Woodpeckers and nesting buzzards. We have placed a Owl box (Tawny Owls are know to be present) and a Pine Marten box there. As the other trees grow we expect the numbers of Woodpeckers, Coal Tits, Goldcrests and Crossbills to increase.
Below this plantation and across Dùn Coillich generally, there are now many berry bearing trees and shrubs that could not exist before the browsing pressure was removed. These include Elder, Hawthorn, Blackthorn, Rowan, Holly and Guelder Rose. Berries attract many bird species such as Redwings, Fieldfares, Mistle Thrushes, Blackbirds and Waxwings. In return for the food that the trees and shrubs provide the birds disperse and plant the seeds in their droppings. We now see Rowans popping up all over Dùn Coillich where they have been planted by birds.
The more barren sheep and deer grazed land beyond Dùn Coillich’s defensive fences play host to Meadow Pipits and Wheatears, but they do not have the many species of warbler that now live in, and adjacent to, the developing woodlands found in a Dùn Coillich. Now there are populations of Willow Warblers, Blackcaps, Grasshopper Warblers, Garden Warblers and, of course, the Whitethroats.
The higher land of Dùn Coillich will have been able to support species such Stonechats, Ring Ouzels, Ravens, Merlins, Golden Eagles and Hen Harriers, but there is no doubt that the protection provided by the Trust has increased their ability to nest. In one year there were more Hen Harriers on Dùn a Coillich than in the whole of England!
Nature is a balance and relationships are complex. There is at least one badgers sett on Dùn Coillich and now Pine Martens are common. These two species along with Ravens and Buzzards may well predate the nests of ground nesting birds such as the Black Grouse and a Hen Harrier, this is how ecology works - it involves a complex web of predator and prey interactions. The badger sett is to found in amongst rocks and their trails and black droppings decorate Dùn Coillich, far and wide. Near the badger sett we have placed an Owl box in a pine tree and it is known to have been occupied by Barn Owls.
Deer are part of the food web, but they must be kept at bay to allow the trees to grow. In the future the trees will be big enough to fend for themselves and the right number of deer can be part of the biodiversity whole. Some day in the future the fences can be removed.
Not all of Dùn a Coillich’s burgeoning biodiversity can be easily seen or heard. In three separate sites there are populations of the endangered Water Vole. These attractive chubby rodents have, throughout Britain, been decimated by the invasive American Mink. The Mink is a member of the weasel family and like weasels, stoats, otters, badgers, pine martens and polecats it is a very efficient hunter. The problem is that when they were released from fur farms by animal activists they found themselves in an ideal habitat with no restraints. They are excellent swimmers and could easily catch the slow swimming and rather bumbling Water Voles (Ratty of Kenneth Williams’s Wind in the Willows tale). The result is that Water Voles have disappeared from most places where they were once common, but not fortunately from Dùn Coillich. They are a high priority for protection.
Dùn Coillich is high and remote and it has deep water-filled channels where the Water Voles remained hidden from Mink. Aberdeen University has been a centre for Mink research and initiated the use of so called ‘Mink Rafts’ in Scotland. These are small rafts, which float on the water and which have a tunnel through which Mink like to run. The tunnel has a floor of clay in which they will leave their footprints. Thus it is possible to know if they are in your area. Fortunately the Dùn Coillich rafts have never detected any Mink.
Water Voles are seldom seen, but they leave signs - they have distinctive middens of dropping and they chew grass and and reeds in a rather precise way leaving a cut end with a 45 degree angle. Although they are secretive they have been photographed using trail cameras.
One iconic Scottish mammal has made a tantalizing appearance on a trail camera on the southern edge of Dùn Coillich. It is the Red Squirrel. Red Squirrels need trees and trees are coming, but are not yet big enough. In a year or two we are hopeful that we will have a resident population of Red Squirrels, feeding on the Hazel Nuts of the Hazel trees which we have planted.
Another rarity, this time a butterfly, finds a home at Dùn Coillich where its complex requirements are satisfied. It is the Pearl Bordered Fritillary. This is an endangered species, which has disappeared from many of its former haunts. It needs Violets, which are the food plants of its caterpillars, Bugle whose nectar feeds the adult butterfly and shelter from dead Bracken stems. Dùn Coillich provides all of these and the Pearl Bordered Fritillary can be seen on the wing from early spring onwards. We have had advice from ‘Butterfly Conservation’ on the management of suitable habitat management for this butterfly.
Beetles may not be glamorous, but there are multitudes of species to be found on Dùn Coillich and three particularly interesting one are - Violet Oil Beetles (Meloe violaceus), GreenTiger Beetles (Cicindella campestris) and Great Diving Beetles (Dytiscus marginalis)
Oil Beetles are large and black with a bulbous abdomen, filled with eggs, in the case of the females. The eggs are laid in the soil and there the tiny larva, called a Triungulin larva, hatches out.It climbs to a flowerhead and awaits a visiting solitary bee. When the unsuspecting bee arrives to collect nectar and pollen the larva attaches itself to the bee and travels back to the bee’s nest where it feeds on the pollen, which was meant for the bee’s own larva. Oil beetles have been in decline with the massive loss of wildflower meadows across the country and some species have disappeared from Britain. The return of flowers to Dùn Coillich is helping maintain numbers of these strange and fascinating beetles.
Tiger beetles, are, as the name suggests, predators. They are large green beetles with yellow spots. On a warm day in July they can be seen hurrying along tracks looking for prey or they may launch at speed into the air, like diminutive six-legged fighter jets, to catch their insect prey in midair. Their larvae live in burrows which which the larva digs for itself. It lurks in the burrow waiting to pounce on passing prey.
The Great Diving Beetle has benefited from the scrapes. Both the aquatic larva and the adult beetle are ferocious predators. The elongate larva lives under water for a long time and feeds on creatures as large a tadpoles and even small fish. It uses the tip of its abdomen to take in air from the surface, rather like having a snorkel. It is equipped with sickle shaped mouthparts, which are hollow. The prey is impaled by the powerful jaws and is injected with enzymes that digest it. The larva then ingests the resultant nutrient soup. The adults are responsible for dispersing the species from pond to pond. They do this by flying at night and looking for shiny surfaces, which ideally would be water reflecting the light of the moon. Mistakes can be made, however, and the beetles may finish up in buckets of water or on a wet road surface.
We know that much of Scotland was once forested where over grazing / browsing and land management for grouse has prevented the growth and return of trees. In spite of this the plants that once lived amongst the trees have often persisted, sometimes sheltering under Bracken, which for them, provides the shade that used to be provided by trees.
Such plants are called woodland indicators. They indicate that Dùn Coillich was once woodland and indeed it is now returning to woodland in many places. The trees are coming back and their ground flora is still there. These woodland indicators include - Wood Anemones, Wood Sorrel, Dog’s Mercury, Dog Violet, Yellow Pimpernel, Chickweed Wintergreen, Bluebells and Wood Cranesbill. All these flowers are found at Dùn Coillich and are flourishing as the trees return. Another way to determine past vegetation is to take cores from peaty areas and see what pollen can be identified from the plants of the past. This is being actively investigated.
Another woodland indicator is the Wood Ant. There is one known nest at Dùn Coillich, which is situated near an old and venerable Rowan tree. The Wood Ants are ‘keystone’ species for the Old Caledonian Pine forest that once covered much of Scotland. They are great predators, but are also very energetic and need carbohydrates, which they get from aphids (Greenfly). This is an example of a relationship known as symbiosis in which both partners benefit. The aphids get some protection from predators such as ladybirds and their larvae and also from parasites such as members of the Ichneumon and Brachonid families of the Hymenoptera. These parasite seek to lay their eggs in the aphid using an extended, needle-like, ovipositor. The parasitic larva then eats out the aphid from the inside.
In return for their protective function ants take sugar-rich honeydew from the aphids. This is a waste product for the aphid, because it takes on more sugars from the sap of plants than it needs.
In the Dùn Coillich scenario the Aphids concerned is Dysaphis sorbi, which makes curled leaf galls from the leaves of the Rowan and the ants then mass around these galls in which the aphids are to be found. It is encouraging to see that this relationship works just as well with the new saplings Rowans as it does with the old, established tree.
It is worth remembering that Dùn Coillich will not be all woodland. There are many other habitats that provide their own biodiversity. There are, for example, flushes and heaths and limestone areas. A recent National Vegetation Classification survey by Ben Averis has identified many important habitats with rare mosses and lichens.
The limestone habitat is particularly interesting as it is based on any unusual limestone - Dalradian Limestone which is about 600 million years old - far older than the Limestone that is to be found on the Pennines in Northern England or the Burren in Ireland. The Dalradian Limestone does not have fossils and has been subjected to heat and pressure in the Caledonian Orogeny, a mountain building process. It may lack fossils, but it does provide the nutrients which lime-loving plants and snails require. The Limestone is largely the mineral calcite which is a form of calcium carbonate. When this mineral is taken up by the Brown-lipped snails (Cepaea nemoralis), of which there are many, they convert it to another calcium carbonate mineral called aragonite to make their shells. The plants which like to grow where the Limestone outcrops occur, include - Thyme, Rock Rose, Yarrow, Lady’s Bedstraw, Oxeye Daisy, Wood Cranesbill, Lesser Knapweed, Bird’s foot Trefoil, Mouse-ear Hawkweed, Fairy Flax, Devil’s bit Scabious and Wood Avens.
Rare plants to come -
The Royal Botanic Gardens in Edinburgh have a project in which they are propagating rare native plants and then finding suitable locations to plant them. As they do this they are conscious of the need to try to increase the genetic diversity of the populations as many have been isolated and will have lost some of this diversity.
Dùn Coillich has suitable habitats for the planting of five rare species -
Small Cow Wheat (Melampyrum sylvaticum), Whorled Solomon’s-Seal (Polygonatum verticillatum), Alpine Blue-Sow-thistle (Cicerbita alpina), Marsh Saxifrage (Saxifraga hirculus), Oblong Woodsia (Woodsia ilvensis).
Dùn Coillich has its own rather rare tree in the form of a Wild (Crab) Apple tree. The Dùn Coillich tree grows,on the banks of the Goulandie Burn and is clearly old. Wild Apples have been studied by Dr Rick Worrell and this particular tree has been part of the study. The only way to be sure of the genetic purity of a particular tree is through a DNA test. If there are domestic Apple trees in the vicinity bees may cross pollinate, leading the resultant apples to be hybrids.
In talking of biodiversity, perhaps the most important component is amongst the least known and understood. It is fungi that are a vital underpinning to every tree through their mycorrhizal connections with tree roots. Very often trees will grow more vigorously if they have the ‘right’ fungal companions. One interesting example is the Alder, which likes to grow in boggy places. Such localities tend to lack nitrogen because denitrifying bacteria turn the nitrates into atmospheric nitrogen and nitrates are lost to the soil. Alder trees are able to ‘fix’ nitrogen - in other words they can take atmospheric nitrogen and turn it into nitrates for their own use, but they can only do this if they have the right fungal partners to help! The intricate connections between fungal mycorrhiza and tree roots has been popularized as the ‘Wood Wide Web’. This is a well known phrase but the implications of this network are, as yet, little understood.
The trees that have been planted come with fungal partners and are a signal to us that although humans like to divide the natural world into discrete groups, in reality all of nature is one entity of mind-boggling complexity.
Richard Paul June 2025