The Bridge at Lerryn dates from mediaeval times. There is a record that in 1573 Queen Elizabeth ordered a levy on the rates for the "erecting and re-edifying the decayed bridge called Laryon between St Vepe and St Winnow". The bridge originally consisted of 3 arches but one has been removed, probably as the river narrowed due to silting from the mining activity upstream.
In 1982, a person with a metal detector found a hoard of 103 Roman coins at Lerryn on the foreshore between the car park and the bridge. The coins date from the 3rd century AD, each featuring the Emperor of the time including Gordian III, Valerian II and Tentricus II. The coins were purchased by the Royal Institution of Cornwall.
The source of the River Lerryn is near West Taphouse and it flows across the Bocconoc Estate where it is joined by a number of small streams, draining from the valleys of the estate. More streams join near Couch's Mill and the river then flows another mile and a half to Lerryn where it enters the ria (flooded river valley) that gives rise to the tidal creeks leading up to Lerryn and St Winnow from the sea at Fowey. At one time, the 4 miles of creek to Lerryn was navigable from the sea by cargo barges. Since then, mining activity in the river valleys has caused the creek to silt up so that it is now only navigable by small boats.
Liverworts grow on the damp, shady wall behind The Granary.
Around 400 million years ago, green algae made its way from the sea to the land and the first liverworts appeared. These ancient, very simple plants are still around today. DNA studies suggest that all land plants and mosses may have originally evolved from early liverworts.
Liverworts are found in damp, shady places but form flat structures that almost resemble soft corals. Their name is based on the appearance of the leaves which was thought to resemble an animal liver. Like mosses, liverworts don't produce flowers but instead reproduce via spores.
Primrose seeds are quite large and therefore, due to their weight, don't travel far from the plant. This causes a clump of primroses to spread out very slowly over time and means it takes a long time for primroses to colonise new areas. This makes large carpets of primroses a very good indicator of ancient woodland where they would have had many hundreds of years to spread out.
A normal healthy leaf contains chemicals which are both green (chlorophyll) and yellow (carotene). If chlorophyll stops being produced, leaves turn yellow. This happens when sunlight is reduced either temporarily (e.g. accidentally leaving something on the lawn) or in autumn when there is less sunlight overall and when cold temperatures also speed up the breakdown of chlorophyll.
The Cornish name for the bird is rudhek from rudh = "red" (in Cornish, "dh" is pronounced like the "th" in "with"). Cornish place names like Bedruthan, Ruthern and Redruth are all based on the colour red.
Despite the pungent smell, the leaves of wild garlic are quite delicate in flavour so can be used quite large quantities in cooking or more sparingly within salads. They are at their most fiery early in the season. As well as a garlic flavour, the leaves have a slight (though not excessive) bitter note which can be balanced against sweet flavours (e.g. tomato or roasted pepper) or salty flavours like bacon to cut through a rich sauce.
Heather plants have a symbiotic relationship with fungi which grows inside and between some of the plant root cells. Up to 80% of the root structure can be made up of fungi. The fungi are able to extract nutrients from poor, acidic soils that plants struggle with. In return, the plant is able to generate other nutrients (e.g. sugars by photosynthesis) that are useful to the fungi. A similar partnership between plants and fungi occurs in lichens.
Mosses are close relatives of the first plants to colonise the land 500 million years ago. They descended originally from freshwater algae but evolved an outer coating that protected them from the temperature changes and UV radiation that made life on the land more of a challenge than in the water. There are now estimated to be over 10,000 species of moss.
Holly was known in Cornwall as the holm (bush) and is the origin of the Holmbush area of St Austell and Holmbush Mine in Kelly Bray.
Ferns produce neither flowers nor seeds and rely on the tiny spores for their reproduction which are most commonly distributed by the wind. This allows them to colonise some quite random places such as rocky ledges that heavier seeds might not reach. Since the spores come from just one parent fern, the offspring is a genetic clone.
The mill is recorded in the 1880s but how long it was here before that is not known. One source suggests as early as 1331 but this may arise from confusion with other mills in the area that were around at the time. The mill was still working in the 1940s but by the late 1970s it was dilapidated although still contained millstones and machinery.
Rosebay willowherb is a tall plant with a spike of pink flowers in late summer which can often be seen beside paths and tracks. Their long leaves have a distinctive thin, white vein along the centre.
Rosebay willowherb is known as fireweed in USA as it's found on burnt sites after forest fires. For similar reasons it was known as London's Ruin after the Great Fire. In the Second World War it was also known as bombweed due to its rapid colonisation of bomb craters.
Ethy woods near Lerryn is part-owned by the National Trust and partly by the government's Forestry Commission. In 2011, the government announced that it would be selling off the woods and there was local concern about the future of the woodland and public access. The government decision was reversed and the woods remain open to the public.
You may remember from school geography lessons that the faster-flowing water around the outside of the bend causes a meander in a river to slowly grow as the outside edge is eroded and sediment is deposited on the inside by slower-moving water. At this point, your school geography teacher probably got excited about ox-bow lakes and never got around to explaining exactly why the water flows faster on the outside in the first place. So that you don't go to your grave feeling short-changed, an attempt at an explanation follows...
Flowing water piles into the outside of the bend and creates a higher pressure there. Close to the riverbed, water is moving very slowly so the high pressure pushes water across the bottom from the outside to the inside. This drags the faster-moving water across the top of the river to the outside to take its place. This spiralling current both erodes the outside edge with faster-moving water and also transports the sediment back across the bottom to the inside
In 2000, an earthenware jar was found beside the creek near Ethy which contained over 1,000 silver Roman coins. It dates from the 3rd Century AD and is now held at the Royal Cornwall Museum, Truro.
The little egret - a white member of the heron family - can be seen on many of the creeks in Cornwall and yet is only a very recent settler in Britain. The birds first appeared in Britain in any number in 1989 and the first to breed was in 1996 in Dorset.
Beside the footpath in Ethy Woods, just as you approach the point, is a worn stone column, covered in lichen. Despite the wear and tear, it is still possible to make out a fluted design and the base for a capital (the tapered head piece that sits between the pillar and the load that it holds). The column is thought to date from mediaeval times and be from an important building such as a church, chapel or manor. At some later point, it was re-used as a gatepost which is why it is flat down one side.
Keep an eye out for kingfishers flying along the river. We saw one here when we were testing the walk.
Kingfishers are found near slow-moving or still water where they dive to catch fish, as their name implies, but they also eat many aquatic insects, ranging from dragonfly nymphs to water beetles.
The Kingfisher is able to switch between light receptors in the main central area of its eye and a forward-facing set when it enters water, allowing it to judge distances accurately underwater. It is estimated that a female needs to eat over twice her own body weight in order to increase her condition sufficiently for egg laying.
The unmistakable metallic blue and orange birds fly fast and low over the surface of the water so may only be apparent as a blue flash. The pigment in their feathers is actually brown but the microstructure of their features results in light interference patterns which generate the brilliant iridescent blue and orange colours. Unfortunately the result, during Victorian times, was that kingfishers were extensively killed for display in glass cases and for use in hat making. The population has since recovered and is now limited by the availability of suitable waterways.
Lerryn's most obvious lime kilns are located on the opposite side of the road from the River Stores but another has been converted into a residence near the end of the walk.
There were four lime kilns at Lerryn, the most obvious of which is beside the road opposite the public toilets. The coal and limestone for these was brought up the creek from the port of Fowey on cargo barges, when the creek was less silted than it is today.
Snowdrops are one of the earliest plants to flower. They use energy stored in their bulbs to generate leaves and flowers during winter, whilst other plants without an energy reserve cannot compete. The downside to flowering so early is that pollinating insects are more scarce, so rather than relying exclusively on seeds, they also spread through bulb division.
Internally, a lime kiln consisted of a conical stone or brick-lined chamber which was loaded from the top with alternating layers of limestone and carbon-rich fuel such as charcoal, peat or coal. At the side of the kiln was an alcove known as an "eye" which was used to access the kiln and remove the quicklime from a hole at the bottom of the chamber. The kiln was often run continuously with more layers of fuel and limestone added to the top as the previous layers worked their way down through the kiln. Air was drawn in through the bottom of the kiln and heated up as it passed through the quicklime (also cooling the quicklime) before it reached the level where combustion was taking place.
The effect of ivy on buildings is controversial as it depends a lot on the properties of the surface it adheres to. The rootlets wedge into any cracks in the surface and so on surfaces that are fragile, ivy will cause damage. A study for English Heritage found that on hard, firm surfaces, ivy did little damage. The blanket of leaves was also found to have beneficial insulating effects and protect the masonry from water, salt and pollution.
Celandine roots have numerous knobbly tubers and when these break off, a new plant can regrow from the tuber. Digging animals such as rabbits and squirrels can therefore help to spread celandines. In some parts of the world they have become an invasive problem where their dense mat of leaves chokes out native species which have not evolved to compete with them.
Lerryn is thought of as a village, despite neither of the churches for the two parishes either side of the river actually being within the settlement.
For a settlement to be considered a village rather than a hamlet it needs to have both a place of worship and a meeting place such as a pub or village hall. There's no clear definition of when a village is considered a town. Many once had markets but now the size of population or presence of a town council can be triggers. However, there are also exceptions to both - one village in England has a population of over 17,000! There are also exceptions to a city needing a cathedral (e.g. Plymouth) - one can instead be created by the King.
Rhododendrons are so successful in Britain that they have become an invasive species, crowding out other flora in the Atlantic oak woodlands. They are able to spread very quickly both through suckering along the ground and by abundant seed production. Many of the root stocks of ornamental specimens have suckered off some new common rhododendrons which have then out-competed the ornamental tree and killed it off!
Conservation organisations now classify the rhododendron explosion as a severe problem and various strategies have been explored to attempt to stop the spread. So far, the most effective method seems to be injecting herbicide into individual plants which is both more precise and effective than blanket cutting or spraying.
Tivoli Park was an area of landscaped created in the 1920s by a China Clay magnate from the village. It was used as the venue for the Lerryn Regatta until 1968 and then the gardens were abandoned. The gardens included a cascading water feature and a bandstand although by the 1930s this was deemed impractical and planted with roses instead. There was also a 200 yard running track, and changing rooms so visitors could wear swimwear to paddle in the fountain. The structures are all built from crude 1920s concrete, decorated with pieces of quartz and broken granite.
The word "beech" is thought to have the same origins as "book" as beech (most probably the bark) was used as a writing material in which to carve runes by Germanic societies before the development of paper. This is still apparent in modern German where the word for "book" is buch and "beech tree" is buche.
The species of duck that you're most likely to encounter is the mallard. Mature males have striking iridescent green heads and dark bodies whilst females look totally different - a brown and white pattern which offers much better camouflage. However, both have a common feature that is unique to mallards - an iridescent blue patch on their wings.
The moon's gravity pulls the water in the oceans towards it causing peaks in the ocean both directly under the moon but also on the opposite side of the Earth so high tides occur every 12-13 hours when the moon is either directly overhead or is on the opposite side. There are therefore just over 6 hours between low and high tide.
Swans usually mate for life, although "divorce" can sometimes occur if there is a nesting failure. The birds can live for over 20 years but in the 20th Century many swans were found to be suffering from lead poisoning. This was tracked down to the tiny "lead shot" weights used for fishing that swans would hoover up with weed and roots from the bottom of rivers and lakes. Since the introduction of non-toxic metals for making fishing weights, incidents of poisoning have disappeared and the swan population is now even growing very slightly.
Wagtails are easily recognised from the tail pumping behaviour that their name suggests. Despite being very conspicuous, the function of this curious behaviour is not well understood. It is possibly a signal to predators that the wagtail has seen them, so there's no point trying anything.
Two of the wagtail species are easy to confuse as they are both grey and yellow.
Grey wagtails nest close to fast-running streams as they feed on aquatic invertebrates. They have pink (skin-coloured) legs.
Yellow wagtails are more often found in open fields and have black legs.
The third kind of wagtail more often seen in urban environments - the pied wagtail - is easy to distinguish due to the lack of yellow: it's entirely black-and-white.
Conifers evolved around 300 million years ago, a long time before the first dinosaurs. For nearly 200 million years, conifers were the dominant form of trees and it wasn't until around 65 million years ago that broadleaf trees were out-competing conifers in many habitats.
Conifer needles contain a waxy coating to retain more water and their shape reduces wind resistance. Both of these help them to colonise exposed upland areas where (unfrozen) water is more scarce. The needles are also less prone to snow damage as snow slides off the young outer needles and only accumulates where needle growth is dense. Conifers do shed their needles but typically keep them for 2-3 years before doing so to economise on the energy needed to create new leaves.
Conifers can produce an economic yield of timber up to 6 times faster than broadleaf trees. Imported species such as Douglas Fir and Sitka Spruce are amongst the more common used for timber production.
It is fairly well-known that conifer plantations support less biodiversity than native broadleaf woods but there are a number of different reasons for this. One is that many of the conifer species are introduced from abroad and the insects that normally accompany them in their native habitat are not present. Another factor is the commercial nature of plantations: some insect species which would live on the trees cause damage to the tree growth and are actively removed as pests. Similarly, plants that compete with the newly-planted trees are removed to allow the commercial crop to succeed. Also the harvesting process means that dead trees do not fall to the forest floor and provide the rotting wood that a range of insects and fungi require.
Like most trees, conifers produce resin to heal wounds. However, conifers also have resin ducts which routinely release it to reduce insect and fungal attacks. As well as including insecticide and fungicide compounds, the resins can also chemically disguise the tree from insects, attract their predators and even emulate hormones to disrupt insect development.
Blobs of resin from conifers can fossilise along with the trees themselves in low oxygen environments to form amber. Over time, the volatile organic compounds that make the resin sticky are lost as the molecules left behind join up into polymers. After a few million years, the result is something very similar to a hard piece of clear plastic. Amber's ability to survive for hundreds of millions of years also suggests that man-made plastics created from organic polymers could persist in the environment a very long time.
The scent of conifer trees mostly comes from volatile organic compounds known as terpenes. Two of the most well-known are limonene (which as its name suggest has a citrus scent) and pinene which advertisers describe as "pine fresh". In fact there are 2 versions of the pinene molecule with the same chemical formula but with a hydrogen atom in a slightly different place. The "alpha" version smells slightly more of pine and is soluble in alcohol and slightly in water. The "beta" version smells more of turpentine and is only soluble in hydrocarbon solvents (e.g. white spirit) so for both reasons is less useful for scented cleaning products and air fresheners than the alpha form.
Bracket fungi can be recognised by tough, woody shelf-like growths known as conks. Some species can live for a very long time and are often coloured with annual growth rings.
Bracket fungi are one of the most important groups of fungi responsible for wood decay. This is good for nutrient cycling but less good if you own a forestry plantation. Many bracket fungi begin on living trees and can eventually kill a branch or whole tree by damaging the heartwood and allowing rot to set in. They can continue to live on the dead wood afterwards and a much more diverse range of species of bracket fungi are found in old natural forests with lots of dead wood.
The ferns with solid leaves are appropriately called hart's tongue as the leaf resembles the tongue of a deer. It is the only native species of fern that doesn't have divided leaves. The Latin name for the species means "centipede" as the underside of the leaves have rows of brown spore cases that form a pattern resembling centipede legs.
Hart's tongue ferns thrive in shady places and are tolerant of the lime used in mortar so are sometimes found growing in old walls. It's an evergreen so leaves can be seen all year round but there's usually a flurry of new growth in mid March when new leaves can be seen gradually unfurling over a number of days.
Squirrels are rodents, closely related to chipmunks and slightly more distantly to dormice. The word "squirrel" originates from an ancient Greek word meaning "shadow-tailed", referring to the bushy tail of a squirrel. A family group of squirrels is known as a "drey" (also the word for a squirrel nest). A group of unrelated squirrels is known as a "scurry", though squirrels tend not to hang out in groups.
Grey squirrels were introduced to the UK from the USA in the late 19th Century and within decades they had replaced the native red squirrel in most parts of the country.
Compared to red squirrels, grey squirrels are able to eat a wider diet (including acorns), are larger so can survive colder winters, and are better able to survive in the fragmented habitats created by urbanisation. They are also thought to be carriers of a squirrel pox virus which they usually recover from but has been fatal to red squirrels, although red squirrels are now also developing some immunity.
To date, culling of grey squirrels has not reversed their domination of woodland habitat and alternative approaches such as planting food with contraceptives are being explored as a means to control the population. The theory is that infertile squirrels can compete for food against fertile squirrels, whereas culling can create a glut of food resulting in a higher number of squirrels surviving which replace those that were exterminated. Natural predators such as goshawks or pine martens also remove more grey squirrels than red squirrels. This is because red squirrels are more savvy having co-evolved with the predators so for example they recognise the scent of pine martens and actively avoid areas with this.
Squirrels assess each of their acorns before burying them. If an acorn is too light (which suggests it might have a hole), the squirrel will eat it immediately rather than risking it going mouldy.
In order to later find the nuts that they've buried, squirrels need to be organised. Some species of squirrel have been studied and found to structure their hoards by type of nut e.g. burying all their acorns under one tree and all their conkers under another. This is equivalent to us organising all the veg onto one shelf of the fridge to make it easier to remember where to look for them.
As well as forgetting where they buried some of them, squirrels may also lose a quarter of their buried food to birds, other rodents and fellow squirrels. Squirrels therefore use dummy tactics to confuse thieves by sometimes just pretending to bury a nut.
Squirrels eyes are positioned on the sides of their head which allows them to spot predators approaching from behind them. When a squirrel spots a predator, its runs away in a zigzag pattern. This confuses many of their predators but unfortunately it doesn't work well for cars.
Young squirrels suffer a high mortality rate in the wild and less than one in three make it to adulthood. The ones that do, live on average for about 6 years, although a lucky one can live to about 12 years old. In captivity, where there are neither predators, cars nor cold winters to contend with, they can reach 20 years old.
By using their tail as a parachute, squirrels are able to survive falls from high trees. This allows them to attempt risky jumps between treetops that don't always work out. They are one of the few mammals that can (but not always) survive an impact at their terminal velocity i.e. if a squirrel jumped out of an aeroplane, it may well survive.
In urban areas in cold countries such as Canada, a black form of the grey squirrel is more common which is able to withstand the cold better both by retaining more heat and also having a slower metabolism. In wilderness areas where predators are more common, the black squirrels don't seem to do so well, perhaps because they are less camouflaged against trees than the grey ones.
For such a widespread tree, the oak is surprisingly inefficient at reproducing naturally. It can take 50 years before the tree has its first crop of acorns and even then, the overwhelming majority of the acorns that it drops are eaten by animals or simply rot on the ground. Squirrels play an important part by burying acorns and occasionally forgetting a few which have a much better chance of growing than on the surface.
The older an oak tree becomes, the more acorns it produces. A 70-80 year old tree can produce thousands. Acorns are high in carbohydrates and as well as being a staple food for squirrels, they are also a really important food for deer and make up a quarter of their diet in the autumn.
Tannins are natural preservatives. The reason why red wine keeps much longer than white is that the grape skins that give the red colour also contain tannins. Oak leaves, wood and acorns all contain a high level of tannins. When wine is aged in oak, the wooden barrels release more preservative tannins into their contents.
The (leather) "tanning" process got its name as it involved extracting the tannins from acorns or oak bark and soaking these into animal hides over 1-2 years to preserve them. From the brown oak juice containing the tannins, the colour "tan" was named and from this the expression "sun tan" arose.
The high levels of tannins in oak make large amounts of oak leaves or acorns poisonous to cattle, horses, sheep, and even goats, but not to pigs as they were domesticated from wild boar which were adapted to foraging in the oak forests, like deer. Acorns were also eaten by people in times of famine. The acorns were soaked in water first to leech out the bitter tannins and could then be made into flour.
Wood from the oak has a lower density than water (so it floats) but has a great strength and hardness, and is very resistant to insect and fungal attack because of its high tannin content. This made it perfect for shipbuilding.
Oak was often associated with the gods of thunder as it was often split by lightning, probably because an oak is often the tallest tree in the area. Oak was also the sacred wood burnt by the druids for their mid-summer sacrifice.
Green woodpeckers are the largest and most colourful of the woodpeckers native to Britain and have a distinctive laughing "yaffle" call. The two species of spotted woodpecker are smaller and usually noticed from the drumming sound they make on trees although they can sometimes be heard making a short "cheep" sound. They are quite shy of humans but can sometimes be seen on garden bird feeders containing fat balls or peanuts.
Of the spotted woodpecker species, the sparrow-sized Lesser Spotted Woodpecker is now not very common. Greater Spotted Woodpeckers are starling-sized and have a white patch at the top of their wings which Lesser Spotted Woodpeckers don't have. Male Greater Spotted Woodpeckers can be recognised from the red patch on the back of the head. Mature female Greater Spotted Woodpeckers don't have a red mark on the head but have the red rump. Juvenile Greater Spotted Woodpeckers have a red mark at the front of their head which can lead to confusion with Lesser Spotted Woodpeckers.
All of the woodpeckers bore holes in trees in which they nest, but only the spotted woodpeckers drill into trees in search of food, spending most of their time perched on a tree. Conversely, green woodpeckers spend most of their time on the ground, hunting for ants. The ants nests are excavated using their strong beak, and then ants are caught on the barbed end of their long tongue. In fact, their tongue is so long that it needs to be curled around their skull to fit inside their head.
The grey heron is an unmistakably massive bird with a 6ft wingspan and yet weighs in at only 1-2kg. The call of the heron is equally unsubtle - a loud croaking "fraaank" noise that is more like grating metal than the sound of birdsong. Herons are most commonly seen in or near freshwater where they hunt for fish. The number of breeding herons has been steadily growing in the UK due to mild winters as they struggle to feed during cold weather when ice forms a barrier on the surface of water.
Although herons primarily eat fish, they will eat frogs, rodents, moles, ducklings and even baby rabbits! They are quite brave birds and will venture into gardens and parks to eat the ornamental fish. They have also been known to visit zoos to steal fish during penguin and seal feeding.
Herons nest in tree-top colonies known as "heronries" where they make a large nest from twigs. It is not unusual for a single tree to contain as many as 10 nests and the overall colony can reach over a hundred nests. The herons re-use their nest for as many years as possible until it gets blown away by a storm. It is unwise to stand beneath a heronry as the birds defend their nests by regurgitating half-digested fish on those below!
In mediaeval Britain, roast heron was a prized dish reserved for aristocratic banquets. In Tudor and Elizabethan times, hunting herons with peregrine falcons was considered a royal sport which resulted in the population being protected from peasants who might otherwise have caught and roasted them.
The English surnames Earnshaw and Hernshaw originally meant "heron wood" and the surname Herne is also a corruption of Heron.
The first trees evolved about 360 million years ago which were a bit like tree versions of mosses. Seeds hadn't evolved at this point and so they reproduced via spores. After the arrival of the seed came conifers which were the dominant form of trees for nearly 200 million years. The flower evolved around 100 million years ago and following this, broadleaf trees appeared and eventually out-competed conifers in many habitats.
Trees grow from a microscopically thin layer of cells that sits between the bark and the wood. On the outside it produces the inner bark (phloem) and on the inside it produces the outer section of wood (xylem).
Trees need a lot of water. A large oak tree can absorb around 450 litres of water per day, most of which is released into the atmosphere as water vapour through transpiration. Trees therefore help to reduce flooding from heavy rain in low-lying river floodplains and also reduce erosion from runoff.
Most of a large tree's trunk is actually made of dead wood known as "heartwood". Only the outer layers (known as sapwood) are actually active. The sapwood transport water and minerals up the tree from the roots to the leaves. The sapwood next to the heartwood gradually fills up with resin and then dies to create another strong layer of heartwood which supports the increasing weight of the tree.
The rate at which a tree grows varies through the year depending on the amount of light and moisture available. This is visible in a sawn tree trunk as a ring where the wider lighter area wood is laid down more quickly in spring-early summer and then the narrow darker area more slowly in late summer-autumn. Each ring corresponds to a year and so the age of the tree can be worked out by counting the rings.
The age of a tree can be roughly estimated by measuring the tree's girth (circumference) at chest height. For conifers (which grow quickly), divide the girth in centimetres by 3.13 for the age in years. For slower-growing hardwood trees such as beech and oak, the value for an isolated tree is 1.88. In woodland, shade from other trees stunts the growth so the girth increases more slowly - by something more like 1.25 cm per year.
The growing conditions for trees varies from year to year (e.g. there might be a drought one summer). The "bad years" and "good years" are reflected in the widths of the rings. The pattern of good and bad summers is the same (more-or-less, depending of the location) for every tree so this forms a calendar - the known sequence of wide and narrow rings can be used to assign an exact year to each ring. This can also be done with dead and even fossil trees both to date them and get an idea of what the climate was doing at the time.
To support their massive weight, trees produce a biochemical compound called lignin which has a cross-linked polymer structure that makes it very rigid. Because it's so tough, most fungi and bacteria are unable to break it down. The main fungus that has worked out a way to do it is known as white rot.
If you don't mind the undignified pose, the height of a tree can apparently be estimated by leaning over and looking backward between your legs, then moving towards/away from the tree until the treetop is only just visible. Then measure the distance along the ground from where you're stood to the tree. Whoever worked out this method of measuring 45 degrees had a strange mind!
The inner bark of the tree carries sugars created by photosynthesis down from the leaves to feed the rest of the tree. The inner bark dies over time to produce the outer bark which protects the living part of the tree.
A thick outer bark on a tree helps to protect it from frost damage during the winter. The bark, which is often textured to trap air, and forms an insulating "buffer zone" that shields the living part of the tree, keeping this above freezing when there are sub-zero temperatures outside. The mass of dense wood inside the tree also acts as night store heater, absorbing heat during the day which is gradually released at night.
When a tree is injured, it exudes resin - a thick, sticky liquid which hardens and seals up the wound. The resin also contains anti-fungal and insecticide chemicals to protect it from parasites and pathogens. Frankincense and myrrh are both examples of resins.
A mature tree can absorb tens of kilograms of carbon dioxide each year adding up to a tonne over a number of decades. However, burning one litre of petrol produces just over 2kg of carbon dioxide so it takes about half an acre of trees to absorb the average amount of carbon dioxide produced by one car in a year. When trees die and decompose, the majority of the carbon is gradually released back into the atmosphere depending on how fast the various bits of tree rot (the woody parts take longer).
The formation of most of the world's coal deposits from wood occurred during a single geological period suitably-named the Carboniferous. It was postulated that this might be because white rot hadn't evolved by then so dead wood just accumulated. However, it's now thought more likely to be due to the formation of particularly deep swamps from the crust-buckling collisions of tectonic plates in this period which allowed wood both to accumulate in a low-oxygen environment and then be compressed into coal.
The blackbird is a species of thrush. The name "blackbird" is mediaeval, first recorded in 1486. Since most of the crow family is also black, plus many seabirds, the choice of this particular species for the name is thought to be due to its size. Up to the 18th Century, larger birds such as crows were referred to as "fowl" and the term "bird" was only used for smaller species.
The Old English name for the blackbird was osle and up to the 17th Century this survived as in alternative names for the blackbird ranging from ouzel to woosel. One of these is used in A Midsummer Night's Dream by Shakespeare: "The Woosell cocke, so blacke of hew, With Orenge-tawny bill".
Only male blackbirds are actually black. The females are brown. The difference in appearance between males and females is known as sexual dimorphism and is an evolutionary strategy by the males to get noticed more by females at the cost of decreased chances of survival.
Blackbirds can be found in deciduous woodland, particularly where there is dense undergrowth. In the man-made landscape, hedges provide plenty of dense undergrowth and have consequently become a really important habitat for blackbirds. Moreover, many gardens have such a high density of hedges and bushes that they are able to support ten times the blackbird population versus an equivalent area of their natural woodland habitat.
Blackbirds are one of the most common birds in the UK with a population of somewhere between 10 and 15 million. However, blackbirds were in steady decline from the 1970s through to the mid-1990s. The population has only relatively recently recovered.
Blackbirds begin singing from around the end of January but it is normally the overkeen young males initially - the older, wiser males wait until March, pacing themselves for the singing period which continues into the early summer. Blackbirds have been shown to sing more during and after rain but exactly why is not yet known.
Baby blackbirds usually leave the nest before they can actually fly then hop and scramble through the bushes. Their parents watch over them so don't attempt to rescue them.
Blackbirds in the UK are resident all year round but the blackbirds that live further north (e.g. in Norway) migrate south for the winter. To help with migration and also to avoid being eaten by predators, blackbirds can sleep half their brain at a time. This allows them to get some rest whilst still maintaining enough alertness to fly or spot predators.
The reference in the nursery rhyme "sing a song a sixpence" to "four and twenty blackbirds baked in a pie" is thought to be to the 16th Century amusement (though not for the blackbirds) of producing a large pie which included an empty chamber. After the pie had been baked and was ready to be served, a trapdoor would be cut in the empty chamber and live birds were placed inside which would fly out when the pie was cut open. Live frogs were sometimes used as an alternative.
In the Christmas carol "The Twelve Days of Christmas", the line "four colly birds" is thought to be from 18th Century slang meaning "black as coal" and was a popular nickname for the blackbird. Whilst many people today sing and write "four calling birds", this is thought to be a modern misunderstanding of what was originally written.
Fungi are often most noticeable when fruiting, either as mushrooms or as moulds but their main part is a network made up of thin branching threads that can run through soil, leaf litter, wood and even living plant tissue.
Fungus is the Latin word for mushroom but is derived from the ancient Greek word for sponge since this is what they were thought to resemble. Biologically, this isn't so far off either as fungi are more closely-related to animals than plants.
95% of all plant life on Earth, including trees, relies on a symbiotic relationship with fungi. It is thought that without fungi, land plants could not have developed at all. Fungal mycelium often grows around or actually within the roots of plants and give the plant access to water and nutrients it couldn't otherwise obtain easily from the soil. In return, the plants provide the fungi with sugars produced through photosynthesis.
By the end of the First World War, Britain had only 5% of its original forest cover left. The Forestry Commission was founded in 1919 to address the timber shortage and bought large amounts of agricultural land, becoming the largest landowner in Britain. As part of the 1968 Countryside Act, the public have been allowed to use many parts of the forestry estate for recreation. Now known as Forestry England, it still plays a key role in woodland creation as part of the government's strategy to increase Britain's tree cover to 12% by 2060.
In tidal rivers, the discharge of freshwater and friction with the riverbed effectively "holds back" the rising tide. The further up the tidal region of the river, the shorter the interval between low and high tide and the faster the rising tide comes in when it eventually does.
Black-headed gulls are found in rivers, lakes and estuaries but rarely on the sea itself, preferring brackish or freshwater.
Despite the name, the head of adults during breeding season (spring and summer) is dark brown. In winter this fades to white with just a small dark dot. During February, dark patches appear and by March most are in their breeding plumage. They are also recognisable by their red beak and legs.
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