Nature 2007 October

An Autumn Rainbow

“I can’t tell you with what pain I think of that autumn at Cholesbury – the yellow leaves – and the wet nights…”.

“Wet nights” – there have been a few of these since my last Nature Notes. The Chilterns and with the exception of Buckingham our county, escaped the worst of the flooding that plagued Gloucestershire, Hereford, Oxford and Berkshire. Rainfall was just over 2 inches far less then elsewhere. Despite this it has been the wettest summer since 1912. Meanwhile hot days were at a premium although we did manage to get to 29°C at the start of August. Looking ahead the Met Office tell us we can expect a slightly warmer and dryer October and November with less wind than normal. This combination of conditions makes it more likely that we will see frequent night-time and early morning foggy conditions.

“Yellow leaves” – do sum up our autumn scene. Mind you given how upside-down the climate has been of late how much yellow we see is anyone’s guess. Trees cannot afford to be extravagant and waste all that energy and the nutrients, which went into producing leaves. So the combined effects of cooler temperatures and shortening day-length trigger the change, which is why it is sometimes prolonged and sometimes brief. What we see when leaves turn from green to yellow and then if weather permits red, is a well-ordered retreat from leaf to sap of all those vital components that were once chlorophyll and the other complex chemicals needed to process all that carbon dioxide. The crimson colouration is a range of pigments called anthocyanins. These are the same colour agents that are found in blackberries, currents, grapes and some vegetables. In the leaves they protect the cell contents from being damaged by ultra violet light in much the same way that a sunscreen works. When again the sap begins to rise in the spring, the tree is well-provisioned to kick-start the new season’s production.

One of the unique sights and sounds of late Autumn, November to be more precise, is the crescendo of whistling and chattering that emanates from a roost of starlings. So characteristic is the display that poets and writers have coined a term for it – a murmuration of starlings. This is no cacophony of noise but a highly synchronised orchestration. The first to arrive select the temporary roost. There is a low level murmur but this does not last for long as soon the early arrivals inaugurate a tune–up session and much as the chorus in the opera may be found throat-gargling clearing their glottis or practicing their chords ahead of the first Act the founding group of players warms up. This draws in further birds and the rest of the flock suddenly descends and the overture begins. There is no obvious choirmaster to direct events but the whole troupe seem to know how they should perform and how to harmonise with their colleagues. The overture ‘finito’… Silence… some birds depart for other roosts, others leave, circle and return and yet more arrive. Act 2 starts louder than before but still muffled and constrained. A further break, more comings and goings and Act 3 commences, louder and more sustained than before. All the birds seem to know this is the final Act, the noise builds to one final crescendo. It is as though they’re all holding simultaneous conversations and with the sweep of the baton the performance ends, suddenly. Darkness is falling and an invisible curtain has come down. There’s no applause, no encore. The birds depart for their night-time roots. No ordinary departure though for these birds instead a twisting, swirling, darting, stalling iridescent cloud of blues, indigo and violet feathers and the drumming from a million wing-beats. So what is this all about? It’s natural for birds to sign-off the day at dusk with their own signature tune. Normally this is a solitary pursuit. Starlings are always on the move both from day-to-day and when migrating long distances. They rely on each other to find sources of food and good shelter. This behaviour serves to reinforce the strength of the community and a successful flock will attract birds in from other flocks. The sudden and highly co-ordinated departure is thought to reduce the treat from predators, such as a sparrowhawk or hobby who may be waiting in the wings to pick-off stragglers that might otherwise be left chasing on behind the flock.

If the warmer weather we had in September continues into October there should be plenty of insects to be seen. Over-wintering butterflies such as Peacocks and Brimstones will be found on blackberries and later the flowers of ivy. Until recently the Red Admiral butterfly was not able to survive winters in the UK. New butterflies arrive from the continent each spring. Now, as long as the weather remains relatively mild, they’ve being found to successful over winter. 16-Spot Orange Ladybirds are particularly gregarious and can be found congregating on the outside of sheds, fence posts and tree bark before migrating en masse into the crevices.

It is the time of year to make some suggestions for Christmas presents. As a youngster a book I remember secreting away off my father’s bookshelf was Food for Free by Richard Mabey. It’s a no-nonsense book, which mixes plenty of information about the plants you can safely eat with traditional stories about them, their uses and the beliefs that were associated with them which were often the source for their names. I am pleased to see it still in print. On a totally different track if you have ever wondered what the names of clouds are and found the reference books difficult to interpret I can suggest the Cloudspotters Guide by Gavin Pretor-Pinney.

By the way the locally apposite quotation above, is from one of England’s most renowned Authors, DH Lawrence. He spent a brief, but emotion-charged period (hence the reference to ‘pain’!) over Autumn and the Christmas 1915/6 with friends at Cholesbury and in nearby Bellingdon. The events of that period are thought to have influenced his writing as he was putting the finishing touches to The Rainbow at the time. His comment above was taken from a letter in 1918 to Mary Cannan who had been living in the Windmill when Lawrence visited.