Horse Chestnuts were recently voted Britain’s favourite tree in a poll organised by the Royal Society of Biology. Around Windsor and Eton, Horse Chestnut trees are a major feature of the local landscape. They dominate the Slough Road approach to Eton alongside Agar’s Plough and are a key feature of Weston’s Yard, with conkers strewn across the footways in the autumn. Horse Chestnuts famously line much of the 4km Long Walk in Windsor Great Park.
Photocredit: Rafał Konieczny, Public Domain, Attribution 3.0 Unported Creative Commons Licence
Unfortunately, Horse Chestnuts are being ravaged by a disease called Bleeding Canker. Just after the millennium, the disease became rampant and by 2007 some 50% of Horse Chestnuts in the UK were affected by a bacterium called Pseudomonas. The Forestry Commission estimates that 35,000 to 50,000 trees are affected countrywide. Interestingly, Pseudomonas comes originally from the Himalayas and is another example, like the Corona virus, of a disease which has jumped from infecting one species (Himalayan Chestnut) to another and then spread around the world. The bacteria multiply within the tubes that carry nutrients up and down the trunk (the phloem) which lie just under the bark, eventually blocking them. This causes the tree to die because it can no longer take up water. Another sign of the disease is dark reddish-brown sticky liquid oozing from cracks in the bark, marking where the infections occur. In dry weather, this dries out to form a rusty-brown or black deposit. Some infections last for years with little effect on the crown, but in other cases it can spread rapidly and can cause the crown to die back and the leaves to turn prematurely brown and drop very early on. Why some Chestnuts are resistant to the infection is not fully understood.
To add insult to injury, UK Horse Chestnut trees have also been seriously threatened by an outbreak of a leaf mining insect. These turn out to be the larvae of a tiny moth (about 5mm long) called Cameraria ohridella. The moth seems to have originated in south-eastern Europe and arrived in UK in 2000: the first outbreak was noticed in Wimbledon in 2002. The moth larva lives in a structure called a mine within the leaf, eating the photosynthetic tissue and weakening the tree, making it even more susceptible to Bacterial Canker. The moth can go through three or four generations in a year and so by the autumn the trees can become covered with the tell-tale unsightly papery brown patches which are characteristic of the disease. With up to 700 mines in a single leaf the effect can be very disfiguring. This is a serious problem given that horse chestnuts are almost exclusively planted for their ornamental value.
Diseases and parasites that spread around the world are very much the result of the global, interconnected world in which we live. The recent Coronavirus outbreak reminds us that such events can be utterly devastating. This is why we need to monitor the living world around us and develop our understanding of the natural world.
By Sarang – Own work, Public Domain, https://commons.wikimedia.org/w/index.php?curid=41997941
Much was made by all the political parties in December’s general election about tree planting to mitigate the effects of climate change. Recently, even Donald Trump has committed to it! However, nobody mentioned the clear and present danger posed by a fungal invader to the 150 million Ash trees that are such a dominant feature of the British landscape. 125 million of these are found in woodland.
The fungus, Hymenoscyphus fraxineus, arrived from Asia into mainland Europe in 1990s. The first official report in Britain came from a nursery in Buckinghamshire in 2014 although research suggests that it was present in UK as early as 2004. The fungus blocks the movement of sap and causes symptoms ranging from leaf spots to branch dieback. Current estimates are that, once infected, some 70 – 85% of Ash trees will die with only a few resistant individuals surviving. The rate at which trees decline once infected varies but a 10 – 15% loss of canopy in a year is typical. Some trees decline much more rapidly. The infection is spread by tiny spores which are produced by fruiting bodies from the stems of fallen ash leaves. The disease is now recorded from two-thirds of England’s geographic area.
Apart from the loss of biodiversity and the change to the look and feel of our countryside, there are likely to be severe economic consequences. Some 4 million Ash trees are found in urban environments (4% of all urban trees) where the risk of falling boughs from diseased trees will present a risk to the public. In addition, Highways England estimate that there are at least 4 million Ash Trees next to the road network, whereas Network Rail believe that there are approximately 400,000 Ash adjacent to railway lines. Many of these will need management in order to make them safe. Some counties like Herefordshire will be severely impacted. Mature Ash trees are thought to account for more than 50% of the non-woodland tree canopy. . The last time anything like this happened in Britain was Dutch elm disease which killed something like 25 million trees in the 1960s and 70s and transformed the landscape.
Eton College has had to restrict visits in response to the Covid-19 outbreak. Unfortunately the Sunday afternoon openings of our museums and galleries are suspended until further notice.
We apologise for the inconvenience and hope to welcome you back soon. Please check our website www.etoncollege.com/CollectionsAccess.aspx or social media accounts for the latest information.
In the meantime, online access to our collections is available at at www.etoncollege.com/collegecollections.aspx and on social media, where we will continue to post content from our museums and galleries:
As Christmas approaches our thoughts may turn to Mistletoe, though its place in our culture almost certainly pre-dates the Christian era. It is a semi-parasitic plant that grows on trees with characteristically leathery leaves and white, sticky, spherical berries. It photosynthesises with its green leaves but it also lives partly off the tree into which it sinks its specially adapted roots. It has tiny flowers from February to April and berries from September into January. The characteristic tight ball-like growths result from the fact that its stem repeatedly forks into two.
A striking infestation of Mistletoe growing on a Horse Chestnut in the garden of The Timbralls, Eton, in April 2019.
Widely distributed across southern England and Wales, it is spread from tree to tree by birds which feed off the white berries and then wipe the viscous material, including the seed, off their beaks and onto branches. It needs a mild, humid climate and trees with relatively soft bark. Mistletoe will grow on a range of hosts, but the usual host trees are Lime, Apple, Hawthorn and Willow. Most Mistletoe for sale these days is imported from northern France, especially from Poplars in Picardy and the orchards of Normandy and Brittany.
As Richard Mabey notes in his excellent book, Flora Britannica: ‘Looking at mistletoe against a low winter sun – the great tresses glistening the colour of tarnished brass, the tiers of twigs like wishbones, the whole plant’s unearthly vitality in the lifeless trees – it is not hard to imagine how it became one of the most revered plants of early herbalists.’ No wonder, then, that in the Middle Ages, it was credited with magical powers and credited with the power to improve human fertility.
Mistletoe is used pharmacologically to treat a variety of conditions such as high blood pressure and recent evidence suggest that at low doses extracts stimulate the immune systems whereas high doses have been used in the treatment of malignant tumours. I hasten to add that self-medication is not to be recommended but kissing underneath it should be safe enough!
George Fussey FRSB FLS FZS
The Thames is the environmental lifeblood of Windsor and Eton and its wellbeing is unquestionably vital for the local balance of nature. It is good to remind ourselves that the ecology of the River Thames has not always been healthy or stable. In 1960s the Thames became so polluted that few fish species could survive and angling became a distant memory. The recovery of the river to its current healthy state is a real success story that we can all be proud of.
But pollution is not the only factor that affects planetary biodiversity and puts species in jeopardy. We are all aware of how illegal trade across international borders has been responsible for bringing species like the White Rhino to the very brink of extinction. But who would have thought that a once familiar fish, which goes by the scientific name of Anguilla, would be affected by the same factor?
Photo of European Eel courtesy of GerardM – http://www.digischool.nl/bi/onderwaterbiologie/, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=284678
The European Eel, once a staple of the Cockney diet (‘Pie and Mash’), is an amazing species. It undertakes one of the longest migrations in the animal kingdom. After hatching in the Sargasso Sea (just south of Bermuda), Anguilla travels over to Europe. As tiny ‘glass eels’ (the name given to the silvery juvenile elvers) they migrate up European rivers, making the difficult switch from a marine environment to a freshwater one. Then, after several years in rivers like the Thames during which they can grow up to 1.5m long, the eels migrate back to the Sargasso Sea to spawn and complete their life cycle.
Two factors have led to the Zoological Society of London declaring the European Eel as a flagship species for nature conservation, following in the footsteps of iconic species like the Giant Panda. The first is that modern rivers now have increasing numbers of barriers to migrating fish. These can take the form of weirs and hydropower turbines.
The second factor which has placed the Eel on the so-called ‘red list’ of critically endangered species is the trade in the juvenile eels which arrive in our estuaries. This is despite an international trade ban. Eels are highly valued in east Asian cuisine and many eel species have declined markedly in recent years. A kilogram of glass eels (numbering about 5,000 elvers) can fetch thousands of pounds. The Japanese reportedly eat 100,000 tons of Unagi, or eels, every year!
George Fussey FRSB FLS FZS
Grey Wagtail courtesy of Dave Bartlett, The Birds of Berkshire Atlas.
Pied Wagtail (male) courtesy of Lisa Carter
If Eton High Street ever wanted to adopt a bird as its mascot, I would select the incredibly adaptable Pied Wagtail over the annoyingly cosmopolitan Pigeon. They are often seen searching for their preferred food of insects and other small invertebrates on the High Street and pavements and are familiar sights in car parks such as Meadow Lane and at local supermarkets. They will feed off insects knocked down by cars but will also forage a crumb or two when hungry. They are impressively bold and have even been known to pick insects off vehicle grilles. Not surprisingly, around bird feeders they favour mealworms.
Our local Pied Wagtails are resident over winter but like to take advantage of communal roosts to stay safe and keep warm. For example, flocks numbering well over 1,000 birds are seen at Heathrow, enjoying the safety from predators conferred by the extra illumination when daylight is at a premium. They benefit from the warmth emanating from buildings which are used virtually 24 – 7 as well as their own collective body warmth. In the breeding season, wagtails rely on cavities of any kind for nest sites and they can be surprisingly hard to locate.
When not in an urban setting they love to forage across gardens and short pasture, flushing out their prey by walking briskly and then taking flies on the wing once disturbed. They often follow livestock in paddocks, living off the flies associated with horses and cattle.
The Latin name of the wagtails, Motacilla, reflects their habit of running about briskly. Motare means ‘to move about’. Their characteristic habit of tail-flicking is not fully understood but there is evidence that such wagging increases in the presence of potential predators and indicates a level of awareness in the birds concerned. This also seems to be true for moorhens, too. Pied Wagtails are almost exclusively British and Irish, being one subspecies of the White Wagtail which has a number of races occupying the Northern Hemisphere.
Other wagtail species are also found in Eton. The Grey Wagtail, which is far more colourful than its name suggests, likes to forage in my riverside garden during the winter, attracted by the fast-flowing water of the nearby mill race. It has distinctive lemon underparts in the winter and a much longer tail than its Pied cousin but is not to be confused with Yellow Wagtails!
George Fussey FRSB FZS FLS
Mistle Thrush Song Thrush
Photos courtesy of Gordon Langsbury (deceased) of Bucks Bird Club.
Throughout the hot weather that we enjoyed this summer, I was ever conscious of how difficult it was for the birds in Eton to keep hydrated and maintain the quality of their diets. Two ever-presents for me were both from the thrush family. We tend to think of all thrushes as having plump breasts with spotted feathers, but in fact thrush species come in many different colours and not all are spotty, by any means. For example, Blackbirds are included in the thrush family, and so were European Robins until very recently.
In my riverside garden, the Song Thrushes love to catch invertebrates and especially snails. These, along with the blueberries and blackberries they steal from my bushes, must provide much-needed moisture to their diet. At least they keep the slug and snail population down and help protect my soft leaved border plants! In the Eton Natural History Museum, there’s a great display showing that some snails are far easier to catch than others. It turns out that the colour and stripiness of snail shells have a huge camouflaging effect on which ones can be seen and caught by thrushes. They break open snails by smashing the shells against a convenient stone, called an ‘anvil’. This habit allows us to know which snail shell patterns they find easier to catch merely by counting the broken shell fragments next to an anvil. As their name suggests, Song Thrushes are renowned for their singing, especially their habit of repeating a variety of phrases. They are also widespread. Settlers Down Under transported the Song Thrush to New Zealand in 1862: they have now become one of the commonest garden birds on both the North and South Islands.
On South Meadow and the nearby Recreation Ground, there have been a handful of Mistle Thrushes around all summer, searching for small invertebrates. Worms retreated so far underground in the dry weather that the thrushes have been restricted to gathering insects. Mistle Thrushes are considerably greyer than the Song Thrush and notably larger. Their outer tail feathers, which are white, are very distinctive in flight. In the winter when resources are scarce Mistle Thrushes are renowned for guarding fruitful bushes from all-comers. Their name is said to come from their love of mistletoe!
George Fussey FRSB, FLS
Photo of a Redpoll courtesy of Phil Tizzard of Bucks Bird Club.
One benefit of extreme weather is that unusual visitors are drawn to my Nyjer seed bird-feeder. Recently, a Lesser Redpoll fed voraciously for a couple of days, happily displacing a charm of Goldfinches that normally enjoys dining rights. Redpolls, like so many small seed-eating birds, have declined massively in the last fifty years. Studies show that the British Redpoll population has dropped by 86% over the period 1970 – 2013, along with similar declines for species like Yellowhammers, Linnets, Bullfinches and Tree and House Sparrows. These declines are largely due to changes in agricultural practices, especially the widespread use of herbicides on arable land. The trend for planting autumn-sown cereals rather than spring-sown has also had a huge effect because fields are no longer left as stubble over winter as they once were. The loss of traditional meadows has also hit these species hard, reminding us how lucky we are locally to be surrounded by hay meadows still managed appropriately by the College. Even the efficiency of modern farming methods has reduced the availability of spilt grain to birds: for example, the average grain spillage from combine harvesters decreased by 90% in the period from 1970 – 2000.
It is not all doom and gloom, however. There are new food sources: oilseed rape seeds form in May and are available for seed-eating birds until they are harvested in July. As well as feeding on farmland seeds, Redpolls also love feasting, sometimes in large flocks, on Birch and Alder seeds, especially by the riverside. In Berkshire, Redpolls have also enjoyed the coniferous plantations and adjacent mixed scrubby heathland.
Redpolls have one of the most glamorous Latin names, by the way: Carduelis cabaret. With a name like that, I am more than happy for this species to put on a show in my garden!
Many residents will have noticed the Black Swan that has been on the Thames in recent weeks. Black Swans were first brought to England in 1791 as ornamental birds (just like peacocks and golden pheasants) but like many other captive species they occasionally escape and breed in the wild. The first recorded breeding in the UK was in 1902 and there is a well-established feral population on the Norfolk Broads. Black Swans bred at Great Meadow Pond in the Great Park in 2004, though it wasn’t until three years later that they successfully fledged. According to ‘The Birds of Berkshire’ (2013), they are occasionally found at local gravel pits and as many as ten have been seen around the junction of the Thames with the Kennet in Reading in recent years.
In fact, the iconic Black Swan is native to the wetlands of south-western and south-eastern Australia and Tasmania. It is the state bird of Western Australia and features on its flag and coat of arms. However, this species has now naturalized in New Zealand where it was deliberately introduced (in 1865) to clear Watercress, itself an alien species. In New Zealand, Black Swans soon spread in the absence of any competition and has numbered 200,000 in recent years, becoming a considerable agricultural pest in the process. Evidence from New Zealand populations is that breeding success becomes greater as the sizes of flocks increase and so it is entirely possible that, in time, Black Swans could compete with, and displace, UK native species.
The spread of species around the world, often aided by man, and not always with any consideration of the consequences, is a familiar tale. Our own Mute Swan has founded wild populations in countries as far apart as USA and Japan. Keeping an eye out for changes in the ranges of species, natural and otherwise, will become ever more necessary in a world of changing climates.
The Museum hosts an annual Secret Life of Birds Family Learning Event for Windsor schools. Always a sell-out, it’s one of my favourite events mostly because, to round off the day, we hire a local falconer to come and fly hawks and falcons around the splendid new McCrum Yard. The children love the spectacle, the chance to get up close to these superbly adapted animals. By the end of the event the children are all able to tell the difference between a hawk and a falcon. Hawks have broad wings without sharp tips, designed for manoeuvrability and kill prey with their talons. Falcons, on the other hand, have narrow wing-tips designed for extreme speed and they generally catch prey with their talons whilst in flight and then kill the prey with their beaks.
The Peregrine Falcon has the distinction of being the fastest recorded animal on the planet, reaching speeds of over 200 mph in the vertical dive (or ‘stoop’). It usually tries to hit one wing of its prey so as not to harm itself on impact. In recent months we have enjoyed sightings of a Peregrine on the south-side of College Chapel. Boys and Masters have also recovered the scant remains of Ring-Necked Parakeets which it has caught. Given that the Parakeets can displace native species from nesting sites and compete with them for food, some local ornithologists are not unhappy to see the Parakeet population under threat!
However, for much of the twentieth century, the Peregrine population has itself been taking a tumble. After the onset of the Second World War, large numbers of Peregrines were killed because they were thought to pose a threat to the military use of homing pigeons with the result that their population was reduced by nearly 50% by 1944. Peregrine populations next suffered in the 50s and 60s from the widespread use of organochlorine pesticides such as DDT. So, all in all, we should take the College Chapel falcon as a welcome sign of recovery.
Photo credit: Mark Fielker