February 2020 - Wildfires and Caterpillar Fungus

Wildfires in Australia are much in the news as I write this, and they will still be burning when I write this column next month.  At least 25 people have died in the fires and thousands are now homeless.  That is tragic enough but the scale of destruction is many orders of magnitude greater for the wildlife affected by the fires.  It has been estimated that more than a billion animals may have perished already.  Bushfires have been a fact of life in Australia for thousands of years and a unique ecology has evolved, not only to cope with fires, but to thrive on them.  I have seen grass trees bursting into leaf when all the rest of the vegetation around them is blackened, and some species of eucalyptus trees will not germinate until the seeds have been charred.  There is even a beetle that can detect infra-red radiation and will seek out burned areas to eat the resulting corpses.  But that ecology has developed to cope with occasional fires that blow through relatively quickly one area at a time.  The current fires are on a different scale altogether where several join up and become large enough to create changes in the weather.  On this scale, even animals that can run or burrow their way out of danger will have no habitat to return to and will probably starve as a result.  The loss is not just about the larger animals, the destruction of insect life, and the detritivores that live in the leaf litter, even the microbes in the soil will have been wiped out.  I have seen several posts from researchers studying particular species such as velvet worms and grasshoppers who are unable to enter the habitats they are studying and suspect that their study subjects may now be extinct.

The cause has been firmly established as global heating, a fact that the Australian government will eventually have to accept however reliant they are on their coal-based economy.  Perhaps the general population will also see that driving V8 cars and screaming about in powerboats is no longer acceptable behaviour.

Closer to home, we are not yet affected by wildfires to any great extent but we are in the middle of one of the wettest winters I have ever experienced and major floods and droughts are becoming commonplace.  All of these are predicted by climate change models and not a week goes by without reports of new records being broken, whether that be ocean temperatures, wind speeds, or atmospheric carbon dioxide concentration.

I am concerned that the wet winter may have affected many species of hibernating insects.  The ground has been waterlogged for many weeks now and the bumblebees, solitary bees and wasps may not survive it.  Insects hibernating underground have to try and choose ground that will not get washed away or flooded or too frozen.  Even if they manage that, places that stay damp can harbour species of fungus that invade their bodies and eat them from the inside.  There is a particular genus of fungus called Cordyceps that invades and even changes the behaviour of insects.  There are hundreds of different species and each one targets a different species of insect.   They can attack both active insects like ants as well as hibernating insects such as beetles.  There is a particular species called Cordyceps militaris that is found throughout the northern hemisphere and is commonly known as the caterpillar fungus.  If you see some bright orange club-shaped fungus (Cordyceps means club-headed) sticking out of your lawn, then if you dig it out carefully you may find the remains of a caterpillar at its base.  This is gruesome for the caterpillar, but looking on the bright side the mycelium is very nutritious for us humans and has many vitamins as well as cancer suppressing properties, not to mention its reputed effect on male performance.

My apologies if you ere expecting a picture of a grass-tree.  I need to go back to 1999 and find the right slide.

January 2020 - Thrushes, Re-wilding

We saw a couple of thrushes on the field at the back recently.  They were quite a distance away so it was difficult to see what sort of thrushes they were even with binoculars.  There are four possibilities for thrush-like birds in this country – song thrush, mistle thrush, redwing and fieldfare.  (The thrush family – Turdidae - is a large family that includes robins, redstarts, wheatears and our more familiar blackbird.)  The redwing and fieldfare are more numerous in the winter as they are joined by immigrants from Scandinavia, but these are distinctive birds – the fieldfare is well marked and has a grey back, and the redwing has a distinctive eye stripe.  The thrushes on the field were not so distinctive which meant they were either mistle thrushes or song thrushes.  The mistle thrush has slightly bolder speckles on its breast and a more upright stance.  I could see both of those characteristics so I guessed at mistle thrush.  This was confirmed when they flew off and I saw a flash of white under their wings.  The four thrushes each have a patch under the wing near the shoulder – which could be called an armpit if there no ornithologists about – that is diagnostic.   The fieldfare and mistle thrush both have a white patch, the song thrush has a buff-coloured patch and the redwing is aptly named.

Song Thrush

Fieldfare  (This one found in its summer residence - Sweden)

Wildlife can be difficult to see as it is, quite rightly, wary of humans.  I saw a book recently that addresses that problem.  It is by Simon Barnes and is called Rewild Yourself.  The theme of the book is things you can do in your garden to attract wildlife.  Rewilding is becoming a popular concept if not a popular way of managing land.  The idea is that larger mammals or predators are introduced to an area which then changes the ecology and allows nature to recover from human intervention.  It is a ‘stepping back’ from nature and is the polar opposite to conservation which seeks to preserve what may already be a degraded habitat.  The Knepp estate in West Sussex and Yellowstone Park in the USA are famous examples of rewilding.  Yellowstone has been hugely successful.  Wolves were reintroduced and the water quality improved!  How so?  Basically, the wolves killed the deer that were overgrazing riverside habitat which meant that the deer couldn’t graze where they could be easy targets.  This allowed trees and bushes to grow, which in turn attracted beavers that built dams which slowed the rivers and allowed fish to thrive and a balance was restored that improved the water quality.  It has had other benefits as well.  Trees and bushes have stabilized the riverbanks and reduced soil erosion, and remarkably, pronghorn deer that were becoming rare are now thriving as there is more grazing available due to the reduction in red deer numbers. (Red deer are called elk in the USA by the way.)  The trees and bushes meant more insects, more birds, and more small mammals and more birds of prey.  This process whereby the introduction of a species at the top of the food chain has a dramatic effect on many other species is called a trophic cascade.

The Knepp estate in West Sussex has had similar success.  No top predators there but free roaming cattle, pigs, deer and ponies have created a mosaic of different habitats that have resulted in thriving populations of purple emperor butterflies, turtle doves and nightingales in little more than a decade.  It’s on our list for a visit in the near future.  Meanwhile we’ll just have to carry on working on our own small patch where just allowing the grass to grow allows a lot more species to get a foothold.  I guess wolves and bears aren’t an option here?

Sadly, I find that I don't have any good pictures of mistle thrush or redwing.  Something I hope  to remedy in the near future.