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.
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.
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.
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.
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.
The path follows the River Lerryn to its confluence with the River Fowey and then follows the Fowey upriver.
The name of the River Fowey is from Fowydh, based on the Cornish word for tree, gwydh, and more specifically beech, fawen.
Amongst the trees planted in the woodland are chestnut, and the nuts are apparent in autumn from their extremely spiky casings.
To roast chestnuts, prick each of your chestnuts with a skewer or slit the shell with a knife - this is vital to stop them exploding (and disappearing into dust). Bake them in a hot oven for at least 10 minutes. Wild chestnuts are harder to shell than the shop-bought variety as the shells are much thinner and the nuts are often smaller. An easier way to separate the edible part from the shell is to simply slice the shell in half and then scoop out the contents with the point of a knife blade. Also this way, the bitter pith covering the outside of the nut is left behind in the shell. The contents of the nut should be fluffy and pale yellow; discard any that are brown. Separating the flesh from the shells is a fairly tedious process, but with a few friends armed with large cups of tea, a formidable amount of chestnut can be extracted which can be used to make stuffings, soups or whizzed into flour and added to bread recipes. It also freezes nicely so it can be stored up for Christmas recipes.
Crows have a vocabulary of different calls with specific meanings and these can be varied to convey emotion like a human tone of voice.
The sounds that crows make have also been found to vary with location rather like regional accents in humans. When a crow moves into a new area, it mimics the calls of the most dominant flock members to fit in with its peer group.
Great tits are most easily identified by their territorial call in spring which is like a whistle followed by two chirps. They have a range of other calls and one theory is that the variation is used to give the impression to rivals that their territory contains several other birds. This is supported by data showing males with the greatest range of calls have more mating success.
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.
You may notice the occasional, and rather large, white shell in the creek-side mud. These are clam shells.
Cockles and clams look fairly similar, but cockles have much thicker shells. There are a few different varieties of various shapes and sizes.
In the cockle department, you're most likely to encounter dog cockles which get their name because they are tough if overcooked; however if cooked correctly they are very good to eat and taste of almond (and are known as Amande de Mer). They have an almost round, slightly ringed shell which is smooth on the outside but has some grooves on the inside edge. The common cockle has a heavily ridged shell, but do not seem to live up to their name in Cornwall.
Clams generally have smoother, more delicate shells. Venus clams have a porcelain-like shell with rings and are about the size of a golf ball. The surf clam is larger, often around the size of your hand and has patterning resembling a mussel.
Cockles and clams can be collected by raking them from the sand at low tide. The Magna Carta grants every English citizen the right to collect up to eight pounds of cockles/clams from the seashore per day.
St Winnow was recorded in the Domesday Book of 1086 as Sanwinnel, and early maps indicate that the churchyard was originally oval in shape, typical of Celtic religions enclosures know as a lann. It is therefore thought that the churchyard may be on the site of the 7th Century chapel of St Winnoc. A stone church was built in the 12th Century and a few traces of this remain in the current church which was built in the 15th Century and restored in the 19th. Much of the stained glass added in the Tudor period survived and can still be seen in the church.
Searches with a metal detector in the fields around St Winnow have unearthed a number of historic artefacts including prehistoric flints, pieces of bronze, Roman brooches and coins, lead seals and musket balls. One of the Roman coins found has been dated to 146 BC, which is a year before the Roman conquest of Britain. It may possibly be from earlier trade links with the Romans.
During the Iron Age and even during Roman times, bronze was still used particularly for items such as jewellery. There were two reasons for this: unlike iron, bronze does not quickly corrode in air and water and the colour and lustre of polished bronze was more attractive than rusty iron.
The Ramblers Association and National Farmers Union suggest some "dos and don'ts" for walkers which we've collated with some info from the local Countryside Access Team.
Do
Don't
If there are sheep in the field and you have a dog, make sure it's securely on its lead (sheep are prone to panic and injuring themselves even if a dog is just being inquisitive). If the sheep start bleating, this means they are scared and they are liable to panic.
If there are pregnant sheep in the field, be particularly sensitive as a scare can cause a miscarriage. If there are sheep in the field with lambs, avoid approaching them closely, making loud noises or walking between a lamb and its mother, as you may provoke the mother to defend her young.
Sheep may look cute but if provoked they can cause serious injury (hence the verb "to ram"). Generally, the best plan is to walk quietly along the hedges and they will move away or ignore you.
Grasses have evolved to grow new leaves from the base of the stem which makes them able to withstand grazing (and mowing). However too much grazing, particularly when grasses are in the process of producing seed, or too much trampling can damage the grass. In the wild, predator species play an important role by chasing herbivores to a new location which gives the grass a chance to recover.
A beef cow produces around 30kg of dung per day. As dairy cows need to eat more to produce milk, they also produce roughly double the amount of dung which adds up to around 20 tonnes per year.
Cow dung is high in nitrogen compounds which makes it a useful fertiliser but depending how this is spread on the fields (e.g. sprayed as a liquid), harmful ammonia can be released into the air and run into watercourses. Large tanks of slurry can also decay anaerobically releasing methane so storage mechanisms are being re-examined in light of climate change.
Hedgerows provide an important habitat for blackbirds.
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.
Anyone who has sat on a holly leaf will know how prickly they can be but the leaves particularly on larger holly bushes often vary considerably with less spiky leaves nearer the top.
Holly is able to vary its leaf shape in response to its environment through a chemical process known as DNA methylation which can be used to switch genes on and off. If its leaves are eaten by grazing animals or trampled by walkers, the holly will crank up the methylation level to produce really spiky leaves on these stems. Conversely on the stems where the leaves are able to grow old in peace, the holly will produce versions that are flatter and therefore more efficient at catching the light. An individual leaf can last up to five years.
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.
Ethy mill dates back to mediaeval times, and was first recorded in 1346, although the ruins you can see today are more recent.
Overshot wheels can achieve higher efficiencies than undershot wheels and can operate using a smaller volume of water which explains why they were generally preferred, particularly in steep-sided Cornish valleys.
A 2004 Civil Engineering publication concluded that high energy conversion efficiencies (of around 85-90%) were possible from overshot waterwheels and that if these can be manufactured cheaply, they could provide an environmentally sound means of small-scale electricity production.
The spore from a fern doesn't grow into a fern. Instead it grows into an organism resembling a liverwort (i.e. a small green blob). Instead of producing spores, these produce eggs and also sperm which they interchange with neighbouring blobs to get a new mix of genes. The fertilised egg grows into a new fern and so this alternating process of ferns and blobs repeats.
Wild garlic grows along the path here. There is also masses of it a short distance along the Lanreath road, near the pub in Lerryn.
Wild garlic can be preserved as a frozen paste for use as a cooking ingredient throughout the year. Simply whizz up roughly chopped leaves in a food processor with enough olive oil to make a fairly thick paste and then freeze this in an ice cube tray (or slightly larger silicone moulds if you have them). Standard cooking olive oil will do for this (it's a waste to use extra-virgin as the powerful garlic will mask its flavour). Turn out the frozen blocks into a bag and keep in the freezer. They can then be used as garlic "stock cubes", added just before the end of cooking.
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.
The settlement of Ethy dates from mediaeval times and was first recorded in 1196 as "Ewthy", which is likely to be a mangling of Cornish words describing the place (the second syllable was possibly chy, meaning "house"). The Ethy estate was owned by the Courtney family who are commemorated in the mediaeval stained glass in St Winnow churchyard. The current Ethy House was built in Georgian times and set in a 18 acre garden. The National Trust acquired over 300 acres of the Ethy estate in 1959, but Ethy House itself is privately owned. Together with Fowey Hall, Ethy House is thought to have provided inspiration for Toad Hall to the author of Wind in The Willows, Kenneth Grahame, who spent much time in Fowey.
As you go through the field gate, note the holly bush on the other side of the gate on the left. In winter, rather than producing the usual bright red berries, the berries on this bush are bright yellow.
The berries of holly contain a chemical compound very similar to caffeine. Only in very small doses is this a stimulant; in larger doses it is toxic. It is for this reason that you see holly berries on bushes rather than being inside the nearest bird. The birds have learned to wait until after the frosts have reduced the toxicity of the berries before eating them.
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.
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.
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 interlaced knot patterns that are associated with Celtic decoration had their origins in the Roman Empire and appear in mosaics during late Roman times. Prior to this, simpler patterns such as spirals and steps featured in Celtic art. Together with Christianity, interlaced patterns were enthusiastically adopted by the Celtic people refined into the knotwork that is now so iconic. Nearly all the decorative patterns are composed from a palette of just 8 elementary knots.
Scholars speculate that the Celtic Cross (a crucifix with a circular ring) developed from the sun cross (a cross inside a circle), a common symbol in artefacts of Prehistoric Europe, particularly during the Neolithic to Bronze Age periods. When Christianity came to the Celtic regions, Christians extended the bottom spoke of this familiar symbol, to remind them of the cross on which their new Saviour was crucified.
Biologically, there is no clear distinction between ducks, geese and swans (geese and swans are one lanky subfamily of ducks). Dark-coloured ducks get the equivalent of "grey hairs" with age - their feathers gradually turn white.
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.
In situations where ducks need to watch out for predators, they can sleep one half of their brain at a time, keeping one eye open for danger. In safer circumstances, ducks will sleep fully.
Male ducks (drakes) have a penis which falls off every autumn and regrows the following spring. The length each year depends on the amount of competition for females and varies up to a maximum of the duck's whole body length.
Ducks can change gender. This happens for about 1 duck in 10,000 and more commonly from female to male than the other way around. It seems to occur in a flock of ducks where there is a significant gender imbalance where it gives the duck that changes a competitive advantage. It's likely that the female to male direction is a bigger evolutionary win because one male can fertilise multiple females.
Feeding bread to ducks is quite bad for them although not feeding ducks anything at all is potentially worse as many have now become reliant on being fed. White bread lacks many of the nutrients that ducks need but ducks will gorge on it to the point of ignoring other foods, effectively becoming junk food addicts. The problem is that by filling up on just this, they can become malnourished, deformed and even die. Some healthier things to feed ducks are leftover peas, sweetcorn, seeds, rice and salad.
Rhododendron is a member of the Ericaceae family to which heathers also belong and like its cousins, it is tolerant of acid soils. The word rhododendron is from the Ancient Greek for "rose tree" due to their spectacular flowers. As a result of these, rhododendrons have been popular ornamental plants for over two centuries and the species that we now call the common rhododendron was introduced in 1763. The plants thrive in the UK climate and were once native but were wiped out by the last Ice Age. Being a vigorous plant, common rhododendron was often used as a root stock onto which more fragile but exotically-coloured hybrids were grafted.
Azalea is a name given to a sub-group of rhododendron species which typically form a bush rather than a large tree. There is no clear biological distinction but most azalea species are deciduous (whereas rhododendrons are evergreen) and azaleas often have smaller leaves, funnel-shaped flowers and are more tolerant of sunny locations than rhododendrons.
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.
A problem with rhododendrons is that they kill bees. Rhododendron nectar is highly toxic to honeybees, killing them within hours. Some other bee species such as mining bees are also adversely affected. Bumblebees seem to be unaffected though.
Honey made with rhododendron pollen can be poisonous to humans, causing severe low blood pressure and low heart rate if enough is eaten. Rhododendron honey is used in Nepal as a hallucinogenic drug.
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.
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.
Compared to many native trees, the beech colonised Great Britain relatively recently, after the last Ice Age around 10,000 years ago. Beech trees have a shallow root system and are therefore often found in areas where water is plentiful such as near rivers. In the 17th and 18th Centuries, tall, stately beech trees were very fashionable in the estates of wealthy landowners and many mature beech woodlands today are the result of 18th Century parkland landscaping projects.
Beech trees can live up to 400 years but the normal range is 150-250 years. Beech trees respond well to pruning and the lifetime of the tree is extended when the tree is pollarded. This was once a common practice and involves cutting all the stems back to a height of about 6ft during the winter when the tree is dormant. The 6ft starting point kept the fresh new growth out of the range of grazing animals. When allowed to grow to full size, a beech tree can reach 80ft tall with a trunk diameter of around 3ft.
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 fruit of the beech tree is known as "mast" or, less cryptically, "beechnuts" and these are not produced until the tree is 40-60 years old. The small triangular nuts are encased in spiky husks which split and drop from the trees from late August to early October. The kernels of these are edible and are similar to hazelnuts. They were once used as a source of flour, which was ground after the tannins had been leached out by soaking them in water. If you find them too bitter, you might want to try this trick, although toasting them in a hot pan is also a good option.
Young beech leaves can be used as a salad vegetable, which are described as being similar to a mild cabbage, though much softer in texture. Older leaves are a bit chewy, as you'd expect.
Beech bark is very delicate and does not heal easily. Consequently some graffiti carved in beech trees is still present from more than a century ago. This is a practice that should be strongly discouraged as it permanently weakens the tree, making attack by insects more likely which can prematurely end its life.
Beechwood ageing is used in the production of Budweiser beer but beech is not the source of flavour. In fact beechwood has a fairly neutral flavour and in the brewing process it is pretreated with baking soda to remove even this. The relatively inert strips of wood are then added to the fermentation vessel where they increase the surface area available for yeast. It is the contact with yeast that produces the flavour in the beer, not the beech itself.
Beechnuts can be used very effectively as a thrifty alternative to pine kernels to make pesto. Collect one trouser pocketful of beechnuts. Shell them over a large cup of tea with a friend, toast the kernels over a medium heat in a dry pan, then grind with a pestle and mortar (surprisingly easy once toasted). Chop 4 sprigs of basil each about the size of your hand - roughly half a supermarket pack. Add to this a finely chopped small clove of garlic and a good pinch of salt and freshly ground black pepper. Then shave (with a peeler) or grate a lump about the size of the end of your thumb of some hard salty cheese such as Pecorino or Parmesan (a supermarket basic range imitation will do fine). Finally add a good slug of extra virgin olive oil and it's time to say "proper job". It makes a ramekin full which doesn't seem a lot but it is so packed with flavour that it goes a surprisingly long way.
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.
Mosses reproduce with tiny spores rather than seeds. Many mosses use wind to carry their spores and produce tiny stalks with the spore-releasing equipment on the top in order to catch the wind - these can be seen as thread-like structures standing up from the moss. These spore-releasing devices often have a ring of teeth around the edge (visible with a magnifying glass) to control the release of the spores, allowing them to be released gradually over a period of time to catch gusts of wind of different speeds and in different directions.
Sphagnum (peat) mosses use compressed air to launch their spores. To get an idea of the acceleration that the spores are launched with, an astronaut in a rocket launch experiences an acceleration g-force of about 3 g and the maximum in a fighter jet is about 9 g. Sphagnum moss spores are accelerated at 36,000 g!
Mosses don't have roots but instead have little rootlets known as rhizoids. Since there is no need to root into soil, mosses can grow on stones, tree trunks, buildings etc. This together with their wind-carried spores makes them excellent colonisers of barren land. The buildup of organic material from dead moss then provides an environment that other small plants can start to colonise.
Mosses' lack of deep roots mean they need to store their own supply of water during dry periods which is why they are found in shady places that are not dried-out by the sun. This also applies to moss on trees - it rarely grows on the south-facing part of the trunk which can be used as a crude form of compass when navigating.
Some mosses are able to absorb 20-30 times their own weight in liquid. Moss was used in several ancient cultures as nappies: babies were carried in a moss-lined bag to prevent leaks. Moss has also traditionally been used to line hanging baskets which are very prone to drying-out. Areas of moss help to protect soil from erosion by runoff and rivers from sediment and flooding by capturing rainfall and giving it chance to soak slowly into the soil.
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.
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.
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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