Nature 2010 August

A song, a smell, the colour purple, and an ailing conker

If the spring is the best time of year to appreciate our beech trees then the summer and early autumn are when to pay attention to another of our locally iconic trees, the horse chestnut. There are an estimated 470,000 horse chestnuts in the UK and we have some magnificent examples of mature trees.

There were once many Elm trees in the area but as we know, in the 1970s, most of these were destroyed by Dutch elm disease. Then, the source of the downfall of the elm was a tiny wood boring beetle which carried a deadly fungus. Sadly, a not dissimilar fate could also befall the chestnut which is being attacked by a disease known as “bleeding canker”. In this case the carrier is not a beetle but a small moth called the leaf miner. The moth only attacks the white-flowered variety of horse chestnut. The red-flowered as well as the pink hybrid are not affected. The first instance of infected trees was in Wimbledon in 2002. Since this time, although concentrated in the South East, it has spread to most parts of England. Trees infected by the leaf miner have leaves with transparent sections which soon die off, leaving a mottled appearance. Meanwhile the canker infection takes hold over several seasons, eventually causing the tree to lose boughs and die back. If you see evidence of the disease it should be reported to Defra.

Perhaps because birdsong is such a normal part of our daily experience, both in our gardens and in the surrounding countryside, we tend to take for granted both the immense range of the sounds different birds produce as well as the complex “lyrics” of songbirds such as blackbirds and song thrushes. Many birds produce a variety of sounds under different circumstances. Birds produce these sounds or songs for different reasons; such as attracting a mate, warning off other birds from their territory, or as an alarm when threatened by a predator. The clue to how birds are capable of producing this vast array of sounds is a unique device called a syrinx. It is similar to our larynx or voice box but, despite the latter enabling us to speak, the syrinx is even more sophisticated.

The syrinx is located at the point where the birds’ airways branch to the lungs. This enables the bird to make two distinct sounds simultaneously. Hence, the tawny owl uses a variety of calls to communicate with its mate or its fledglings, the starling mimics a mobile phone ringtone or, for that matter, the African Grey Parrot “talks” to its owner. One thing we do share with birds is the way in which our respective babies learn to communicate from interaction with their parents. Through imitation, listening and practising young birds and children learn the complex grammar and rules of communication. Apparently, according to researchers, birds also share with humans the sound of their own voices and sing “for the joy of it”.

In the last Nature Notes I referred to the associations between some animals and plants either because of the similarity of certain features or because of a link for medicinal purposes. In a similar vein the names of some butterflies have an interesting origin. Many of the names came about during the 18th and 19th centuries when collecting butterflies, moths and beetles was a “sport” of gentlemen. This accounts for some of the more curious or exotic names. The gatekeeper was so named because the male defends a territory, chasing off any rival males who dare approach too close. The marbled white was, during the Victorian period, known as the “half-mourner” on account of the fashion of women in mourning to wear a mixture of black and white clothing.

Some members of the fritillary family of butterflies have interesting names. The family are so-named because of the chequered markings which resemble the snakes head fritillary flower. The Queen of Spain fritillary was so called by a collector in the 1700s because of the large number of silver markings which were seen akin to the vast riches of the Spanish monarchy. A related butterfly was named after an eccentric female collector, Eleanor Glanville. Sadly, after her death her notoriety as a fanatical collector was used to contest the validity of the will she had made on grounds of her clear insanity – a woman who collected butterflies! One quite rare butterfly which has been sighted in the local area is the purple emperor. This is one of the most spectacular of butterflies. It was given its name by a 19th century entomologist because he was struck by the similarity of the purple to robes containing Tyrian purple, a rare and expensive dye also known as imperial purple extracted from marine snails and only worn by royalty and such like.

Late August and September brings one distinctive smell to those who walk the footpaths and woodlands. The musty odour of the stinkhorn is not one that you can readily warm to, however often one comes across it. The sole purpose of the essence is to attract flies and beetles to spread its sticky spores in the neighbouring area.