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By Martyn Stenning
December 2019
Leaf fall is well underway as I write in early November. This is triggered in deciduous plants by the reduction of daylight as the days get shorter. The process is called abscission which is an active and deliberate process. Abscission is caused by the cells of the stem, from which the leaf is growing, pushing the leaf stem (petiole) off when it is no longer needed. Nutrients from the breakdown of green chlorophyll will have already been reabsorbed by this time to feed the tree or other plant; this is why the leaves change colour before they are shed revealing the showering yellows and reds of autumn.
Have you noticed how the different species of tree lose their leaves at different rates? Currently, the black poplar trees in Hempstead Meadows Nature Reserve have lost almost 100% of their leaves. Similarly, ash trees have lost about 70% of theirs, but some of this may be due to ash die-back disease, which is spreading rapidly through the trees of Sussex. There will be individuals that are resistant to the disease and survive to repopulate in due course. This is called natural selection. However, the oaks have only defoliated about 8% of their leaves. Indeed, some species of oak are actually (semi-) evergreen, such as the holm oak, which is not native to Britain, but lives naturally in Southern Europe. Holm oaks only renew about 30% of their leaves each year.
Mean-while, back to the current state of the deciduous trees in Uckfield, sycamore trees have lost about 50% of their leaves, horse chestnut about 30%, beech about 20%, the limes of Lime Tree Avenue about 30%, birch about 40%, but this tree is very variable. Finally, the sweet chestnut trees of Hempstead Lane have only lost about 30% of their leaves.
Another thing I have noticed about the trees is that they shed their seeds before they let their leaves go. This is probably a deliberate strategy to maximise the generation of nutrients from the leaves to bulk out the seeds, which can be quite large, such as the horse and sweet chestnuts, acorns and beech nuts. Other seeds such as the tiny birch seeds are light and more plentiful and can be carried long distances by the wind.
November 2019
In October we can notice many changes in Nature. The weather is often unsettled. The days are noticeably shorter and cooler, the leaves on the trees of old England are changing colour and thinning out. Insects are getting scarcer and many are being caught by the seasonal abundance of Arachnids, such as the orb web spiders.
Birds such as willow warblers and swallows are migrating away from us to their summer quarters; many more, such as wheatears and pied flycatchers are passing through on migration to Africa. Other birds such as Brent geese, teal, pochard and pintail ducks plus many species of waders such as dunlin, grey plover and curlew are arriving from their Arctic and eastern breeding grounds to spend the winter on English estuaries and waterways. Mammals, like us, are preparing for the cold winter by storing food, growing thicker pelts and putting on weight by feeding on Autumn’s season of plenty. Some of these such as bats, hedgehogs and dormice will hibernate for months. Others, such as foxes, badgers, squirrels and mice will simply feed up and spend more time sleeping and foraging for food. The badger females are likely to mate and be pregnant in October and will suspend embryo development for a while until late December. The badger embryos take 49 days to develop leading to births (about 3 per female) underground in February.
The reptiles such as our common lizards, slow worms, grass snakes and adders have slowed down so much, in the coolness of Autumn, that they are compelled to hibernate in a secure cavity underground somewhere. Reptiles, insects, spiders and other invertebrates are poikilothermic or cold blooded, which means that their body temperature is not internally regulated like ours, our mammal relatives and birds. Likewise, the amphibians such as frogs, toads and newts. These too will slow down with the falling temperature and find somewhere damp and free from frost to hibernate until early Spring.
We humans do not have to mow the lawn so frequently, because the grass has no need to grow very much in the Autumn. We get tired easily, our skin may go paler and we wear more and warmer clothes. Our diet may also change with fewer salads and more hot soups.
October 2019
Early this morning I was privileged to see 2 black storks flying over fields near our house in France on their way to Africa. These are rare, shy birds that nest atop tall trees in remote northern Eurasian forests. Recently, I have also seen white storks going the same way. White storks are not shy, however, and tend to nest on church towers and other high buildings, trees and pylons across Europe, but only rarely in Britain. Also, I’ve seen wheatears passing to a similar destination from northern latitudes. Pied and spotted flycatchers have been sallying forth from our elm trees to catch flying insects on the wing as they sojourn before flying to West Africa. Swallows and other hirundines have also been gathering on overhead cables ready to fly as far as South Africa. These are in turn hunted by a small falcon called the hobby.
Chiffchaffs, a type of small leaf warbler, still sing their name as they migrate south, past where we are. You may also hear them in Sussex as they head for the coast and beyond. Chattering starlings are also gathering. They do not usually migrate far, but they can form vast flocks that fly at sunset wheeling and diving like a single organism, often chattering as they do so, in an aerial dance called a murmoration.
It is not often realised that some butterflies also migrate south in the autumn. One of these is the painted lady. Painted ladies donate their Latin names to humans as they are in the genus Vanessa and the sub-genus Cynthia. Apparently, they often fly south to Africa in the autumn and back to Europe in the spring. Considering that they cross the English Channel, the continent, then the Mediterranean followed by the Sahara Desert, it is an incredible journey for a tiny butterfly. Some may be taken in flight by insectivorous birds making the same journey, but others clearly succeed as the annual routine continues.
There is a plant that is also a harbinger of autumn that also has a feminine name and that is autumn ladies tresses. This is a delicate white orchid that can turn up almost anywhere, but usually in low numbers. Like most orchids, the seeds are profuse but tiny, like grains of dust and settle everywhere, but only a few survive to flower. I have even seen them flowering in Manor Park, Uckfield. They are fairly frequent on the chalk Sussex Downs where the grass is short. Their charming Latin name is Spiranthes spiralis.
September 2019
Nature Notes are usually written a month or more before you see them, so they may sometimes seem a bit out of date. I am currently writing these in France on August 9th. By September, autumn will have started and the leaves of some trees will have begun to turn and blackberries will be adorning the hedgerows.
Currently, France is experiencing a series of “canicules”. These are heat waves or mounds of hot air moving north from the Sahara Desert through Europe. The temperature at night remains hot at more than 25 degrees Celsius. The daytime temperature reaches the high thirties.
Now is the time for insects. In France, cicadas “zizz” from the tree tops with bush crickets and grasshoppers stridulating from hedgerows and grass. Butterflies such as swallowtails, gate keepers, clouded yellows, red admirals and small blues adorn flowers. Solitary and social bees and wasps hunt for nectar and meat among the living and dead animals that they can find. Female mosquitoes and midges hunt for a blood meal from humans and other vertebrates so that they can produce and lay eggs. Furthermore, spiders (not insects of course) form gossamer traps for these in and out of our houses - a mixed blessing. Lizards also hunt for small creatures, but usually insects like ants and butterflies. Birds too hunt aerially or glean the tree tops for insects. Even in mid-august some of insectivorous birds are migrating back to Africa. Most swifts have gone, but I saw 2 late ones this morning.
The cycle of life in the natural world is both delicate and robust. If we disturb an animal when it is breeding or eliminate insects with poison, we remove elements of a dynamic ecosystem. We depend on these ecosystems for services such as oxygen from green plants and plankton, pollination of fruit and vegetable plants, the decay of waste and the formation of fertile soils by dung beetles, worms and bacteria etc and even the regulatory control of insect populations by birds and spiders. All these things are happening spontaneously, but many of these systems are becoming unbalanced due to our excesses of modern living. Sadly, climate change is now a stark reality, species decline and extinction also. However, as far as nature is concerned, these are simply changes that open up niches for new organisms. As such, Nature is robust and will continue, but if we are to do the same, I believe we must take our lessons from nature rather than abuse it.
August 2019
It is now high summer, mid-July as I write. I have just returned from a 1100 km eight week walk in the wilds of southern France and northern Spain along the pilgrimage routs of the Camino de Santiago de Compostela. The habitats and wildlife that I encountered along the way were frequently amazing. We started by walking across the very flat and sandy forest of Landes de Gascogne in Aquitaine, just a few metres above sea level. This is reputed to be the largest forest in Europe, and has been a source of French timber for several hundred years. Much of the forest is planted maritime pine, but the natural ecosystem is oak dominated woodland, with strawberry trees and heathers, which still persist in much of the area. I was amazed at the number of nightingales that I heard singing, not only in the French forests but also along Spanish sections of the Camino. There were also many wood warblers, both of the afore-mentioned species are increasingly rare in Britain.
A very rare plant that I have studied in Sussex because of its rarity called the spiked rampion was also frequently encountered along the French part of the Camino. Similarly, I studied the very rare early spider orchid on the South Downs near Brighton, but these were also frequently encountered along both the French and Spanish sections of the Camino.
Once out of Aquitaine, we were in the Pyrenean mountains where we quickly encountered vultures, black and red kites and other birds of prey. However, the weather was so challenging with rain, wind and cold that it was not very conducive to nature study. Once over the Pyrenees we were on the high plains and further mountains of Northern Spain, encountering altitudes up to 1500 metres above sea level. The wild flowers in these areas were truly amazing, along with further rare birds such as the red-backed shrike, crested larks, cetti’s warblers and cirl buntings. One of the most remarkable encounters was at the many churches along the Spanish Camino, the majority of which had one or more pairs of white storks breeding on the roofs and spires. Most of these were seen during May and June after arriving from their African wintering quarters, and had quite large nestlings. The adults, which are very mate faithful and long-lived, greeted each other frequently with clackering of their beaks sounding like the banging of a hollow log with drumsticks.
May 2019
Well, spring has well and truly sprung now and even the oak trees now have leaves changing the tree-scape from the greys and browns of winter to the greens of summer. April, May and June are an intensive period of regeneration in nature, a time when lawns have to be mown regularly, because if they are not, they would turn into a hay field. Hay-making traditionally starts in June when the grasses are ripe and full of energy for feeding to live-stock during the rest of the year when required. If the hay is not cut, succession starts as seeds from other larger species of plants such as acorns from oak trees germinate among the grass-roots and attempt to create an oak woodland.
Every grassland hides a forest trying to get out. If it does, this is called succession. Succession id helped by the animals that visit the grassland, especially the birds. Oak jays are especially adapted to recreate oak woodlands. In the autumn, oak jays obsessively collect acorns from under the oak trees and carry them in a pouch below their beak to an open area (field) and plant them in the soil, ostensibly as a potential cache for the future, but in reality, many are not re-found and germinate. These will get mown down by the next hay-cut, but if the hay is not cut, will develop a new forest. Black-berries will also be eaten from the brambles in the hedgerows by field-mice which will also roam the fields looking for other food. In the process, the tiny seeds will pass through the mice and be expelled, still viable, in the mouse droppings and will germinate among the grasses. Thus, the brambles will also spread into the fields to protect the young oak trees. The many thrush species such as song thrushes, mistle thrushes, blackbirds, redwings and fieldfares will eat the hawthorn berries (haws) in the winter and likewise disperse the seeds in their droppings as they also fly over or forage in the fields. So, young oaks, brambles and hawthorn trees are common successors to grassland and will rapidly grow to create a new woodland. However, it takes centuries to create an ancient woodland in which dozens or scores of other plant species will develop as the cycle of life continues with old trees dying or being blown over to create new clearings into which new species will be introduced by woodland animals and wind such the seed of willows and poplars. Not so much wind in the willows as willows in the wind.
April 2019
“Spring is coming, spring is coming, birdies build your nests, weave together straw and feather, doing each your best”.
This is a little ditty that my mother used to quote to us at this time of year when we were very young. I am not sure where it came from. The fact is, I am writing this on 17th March, just 4 days from the Spring Equinox when daylength will equal night length the world over. Nature senses this, and in the northern hemisphere buds are breaking on the shrubs, which usually happens before the large trees. Bulbs such as crocuses, daffodils and tulips are sending up their stems and leaves in that order. Our local jackdaws are building their nest in a neighbour’s chimney and the carrion crows are watching to see if they can steal their eggs. Frog spawn has been laid in the ponds and tadpoles are developing. Also, newts are also in the ponds pairing up and laying their eggs in the leaves of water plants.
Spring can be a very personal experience making people smile and surprising us with its perennial rebirth of nature’s abundant life. This morning, the dawn chorus was particularly loud with numerous local Eurasian blackbirds harmonising with descant singing Eurasian wrens. The blue tits are exploring nest-boxes that people have erected in their gardens, parks and woodlands in order to help them breed successfully. Let’s face it, we do love nature when it is like this. It is even important for our health to visit natural areas regularly for a sense of wellbeing and to breathe the clean oxygen emanating from the green plants on which we all depend. Environmental services often go unrecognised until they start to decline. We have had many warnings recently about Human generated (anthropogenic) climate change causing the death of marine coral and the generation of devastating weather events such as fires in California, drought and floods in Australia and mud-slides in South America. Closer to home, we had record temperatures (c. 210 Celsius) during February. We may experience water shortages later in the year. Let’s also remember that these events affect all nature, not only us Humans. Maybe the time has come to address this issue at a personal level. If all 7.5 billion people world-wide acted to reverse negative our effects on the environment, the problem could be solved?
March 2019
Like many birds, I have migrated south for at least part of the winter. I am at Latitude 44°N and if you are reading this in Sussex, you are at about Latitude 50°N. Just for reference the arctic circle is at about 70°N Yes, I am in France again. It is February 13th today and I have been busy mowing the lawn and scaring the sunbathing wall lizards. The occasional brimstone and peacock butterfly was fluttering by as I worked. Yesterday we watched a flock of about 50 common cranes fly over the house on their way north to their breeding grounds. I also watched a black carpenter bee visit the Aubretia flowers on the verandah. However, it has not been all like this, proximity to the Bay of Biscay means that we had about 2 weeks of almost continuous rain until recently. The ditches and rivers are all full and the frogs have been filling them even fuller with their spawn.
The tilting of the earth means that the days are lengthening by a few minutes with each one. I suspect we are all looking forward to the “lazy, hazy, crazy days of summer”. Barn owls and mistle thrushes will be preparing nests as I write. Blackbirds, blue tits and robins will also be showing themselves in pairs as they court and test each other’s credentials as a prospective breeding mate.
Until spring really gets going, finding food is a real problem for any animal in the wild. Diurnal animals will have short days for hunting, long cold nights to get through and many will die leaving only the resilient to pass on another generation.
In ecology, we often say there is no such thing as a disaster, only change. What we humans see as a disastrous storm or cold spell is simply a change in the environment leading to opportunities for some organisms and challenging conditions for others. Cold winters generate cold resilient animals such as polar bears, arctic foxes and reindeer. Hurricane force winds lead to many fallen trees and plenty of dead wood leading to a population explosion of wood boring beetles an increase in woodpeckers that eat them and so on. Even hot weather leads to the generation of heat resilient plants and animals such as cacti and camels. The result is a world full of variety and change.
February 2019
I would like to focus on tortoises this month. These animals are in a group of reptiles called Chelonians that also includes turtles and terrapins. Tortoises have existed since before the dinosaurs, that is, they appeared on the earth about 220 million years ago.
There are at least 3 species of Mediterranean tortoise, and during the 1950s and 1960s many of these animals were collected and brought to England in large numbers then sold in pet shops. Thankfully, this practice is now illegal. However, many tortoises remained stranded on our north Atlantic island which is warm enough for them to survive but too cold for them to breed, so their gene line is destined to die out. All we can do is take good care of them and try to give them a good life.
Thankfully, there are organisations in the Mediterranean region that are helping the wild populations to recover. Also, some British owners are incubating eggs laid by their tortoises in incubators and hatching them out in captivity, but it is a labour-intensive practice and takes a great deal of time and care. The young tortoises have to be kept under electric lamps for many years.
Tortoises hibernate from about October to April. They naturally and instinctively bury themselves in the ground, which generally remains warmer than the winter air. It is generally believed now that allowing them to do this naturally, rather than packing them away in a hay-box is better for the tortoise. The tortoises heart-beat slows-down and they enter a state of torpor. However, if it gets very cold, they can dig themselves in deeper if necessary. Then, when the sun begins to warm the ground during March/April the tortoises gradually heave themselves out of the soil and find a place to sunbathe which warms up their bodies allowing them to search out food and water.
Tortoises eat a range of herbs including dandelions, sow thistles, wild lettuce and grasses. They will also feed on the occasional dead animal as a protein supplement. They do live a very long time, and it is not unusual for tortoises to live well beyond 100 years.
January 2019
At a time when some trees and bushes are producing berries I think it is worth thinking about why this happens during Autumn and Winter. We celebrate the holly, ivy and mistletoe at Christmas, but these berries are not appearing now by accident.
Winter is a difficult time for birds, and a time when mortality is high, and the individuals that are best adapted to survival will get through to Spring and attempt to reproduce.
However, the berries are there at this time, not specifically out of altruism to provide food for these birds, rather they are enrolling the birds as seed dispersers and winged conveyers of the plant’s offspring. A bit like the proverbial stork delivering babies.
The three plant species mentioned could not look more different. Holly is our only evergreen broad-leaved tree (if you do not count box which is really a shrub). In fact, all three are evergreen. Also, Holly like the other two is dioecious – has male and female plants and only females have berries of course. Ivy is an evergreen liana climber and mistletoe is a parasitic plant that taps into a host tree’s vascular system. All three produce berries during the autumn and winter.
Many birds overwinter in Britain because of our temperate climate, but also because there is food to be had in the form of a bribe offered by the above plants and others like hawthorn (haws) and rose bushes (hips). The berries are eaten, often whole, and the tasty nutricious coating is digested. However, the seeds pass through the bird’s body and emerge in a tiny packet of compost, often while the bird is roosting in a bush at night, but just as often when flying or looking for more food. The seeds then germinate in the spring and a new generation of the plants is produced in a new location.
This relationship has persisted because all members of the partnership benefit. Moreover, the benefits lead on to successful reproduction meaning that the tradition is perpetuated into future generations.