Nature 2009 August

September sights and sounds; spangling, semaphore, sheaves, shucks and swallows

The weather conditions in North Africa are not my usual starting point I admit. However, the wet winter season in Morocco has provided us with a ‘once in a decade’ display of spangling colour. Painted Lady butterflies are not a resident species in the UK; well at least they’re not for the present anyway. Each year we rely on the northern migration of this distinctive butterfly. It is one of the most widespread and well-travelled butterfly tribes around the globe and is related to another migrant, the Red Admiral. Both belong to a genus called Vanessa, the girl’s name which had been coined by Jonathan Swift around 1700.

Anyway, the unusually heavy rainfall in February caused a verdant covering of food-plant in the Atlas Mountains which in turn supported an abnormally large herd of rapacious caterpillars. Emerging a month later from bejewelled chrysalises, the adults departed northwards to France, Spain and Portugal. A second generation left from there northwards. This year, rather than just tens-of-thousands, up to a million or more arrived across the UK. They have been reported as far north as the remoter Scottish Islands and although they prefer open ground they have been plentiful in the more secluded parts of the Chilterns.

In July these generally non-gregarious caterpillars – which are black/grey spiky with a pale cream stripe along each flank (Peacock butterfly larva is a glossy black) – could be found feeding on thistle and nettle. By the time this imago edition of HTN emerges through your letterbox, the British-born generation of Moorish imagoes should also be about to emerge too. So keep an eye out for this large showy butterfly with its characteristic speedy corkscrew flight pattern.

This UK-born generation do not breed here but disappear and there is debate as to their next destination. Although it has been suggested they head southwards again, there’s no confirmation of the theory that they actually return safely back in North Africa. Lepidopterists are hoping to crack this mystery later this year.

This mystery has a parallel with one which puzzled naturalists over 200 years ago. Then there was a theory about where swallows went in winter. The collective view was that they buried themselves in muddy banks until the spring. Today there is no doubt where swallows go in winter. On warm September evenings they can be seen feeding up on the clouds of insects drifting on the thermals and at dusk congressing as they masse together on overhead wires ahead of their synchronised departure for southern Africa.

A year or so back I commented on the absence of lapwings from our fields in more recent times. This year there have been sightings in an arable field in Heath End and I was also lucky enough, while walking the parish boundary, to see a pair performing a haphazard display, from which they get their name, and aimed at distracting would-be predators from finding their chick(s). Their black and white wings seemingly using a unique semaphore to beat out their message. These were a welcome sight as the lapwing is one indicator of how well or otherwise the local wildlife is faring.

We tend to associate owls with the hours between twilight and dawn and conversely not birds ‘of the day’. Tawny owls break this rule. Fledgling tawnies leave the nest early, after five weeks and far too early perhaps, as they then hang around perched on branches in nearby trees for up to three months, relying on their parents to feed them. I think this is akin to serving a kind of apprenticeship whereby the youngsters supposedly are learning how to lay up motionless and unnoticed during the day. However, like all young children, they crave attention and are given to break cover with spontaneous outbursts along the lines of “Keewik” in the middle of the day. Once heard, look out for a gawky-looking fluff ball trying feebly to appear inconspicuous.

To be honest, being a scientist, my appreciation of our English poets had until now sadly not stretched as far as John Drinkwater, whose works were influenced both by his childhood in the Warwickshire countryside and the later horrors of the First World War. I happened across the following poem, called September, which not only reflects these influences and the time of year but is of particular relevance for another unexpected reason. The verses are believed to have been inspired by the countryside around here, experienced during a short visit in 1915/6. But that’s a story I will save for another time, wearing my local rather than natural history hat on!

Wind and the robin’s note to-day
Have heard of autumn and betray
The green long reign of summer.
The rust is falling on the leaves,
September stands beside the sheaves,
The new, the happy comer.
Not sad my season of the red
And russet orchards gaily spread
From Cholesbury to Cooming,
Nor sad when twilit valley trees
Are ships becalmed on misty seas,
And beetles go abooming.
Now soon shall come the morning crowds
Of starlings, soon the coloured clouds
From oak and ash and willow,
And soon the thorn and briar shall be
Rich in their crimson livery,
In scarlet and in yellow.

Almost 100 years on, many of these September sights (and sounds) around our villages have changed. There are but a few remnants of those ‘russet orchards’ and the image of sheaves is an even more distant memory. Although these elements of Drinkwater’s rural idyll may have disappeared, the autumnal woodland vista and hedgerows described in his third verse still remain very much part of our September scene today, except where they have been replaced by a monoculture of sterile trees.

So perhaps while out one late September day you’ll catch that first glimpse of this year’s ‘clouds’ and realise the timelessness of that view. Meanwhile, there’s also that distinctive crunch underfoot as you walk on the remains of nutshells, beneath a hazelnut tree. Those discarded by squirrels have been splintered in their jaws. Others more intact have a circular hole and teethmarks, having been gnawed through by wood or yellow-necked mice. Amongst the discarded shucks may also be some shells with a tiny circular hole bored in them. This is the work of a third consumer, the nut weevil. One egg is laid by the adult beetle when the shell was small and soft. The larva feeds on the growing nut and, having drilled its way out, continues the journey to adulthood over-wintering under an insulated blanket of leaves.

Thinking of entering a photo in this year’s Hort Soc Show? Some well-positioned over-ripe fruit, such as bananas or plums is an excellent way to attract those large butterflies to the garden and get them to keep still while you photograph them. Happy snapping!