Through the fog, I saw a strange thing ...

IT’S been a winter of extreme weather.

The latest in my part of the midlands has been a series of heavy fogs.

Typically, the fog arrives at night, and, if it clears after dawn and there has been a frost, the day turns into a winter wonderland, every twig sparkling white in the sunshine. Some days it doesn’t clear – it lasts for three or four days and nights, giving the countryside an eerie, post-apocalyptic feel.

Walking across the yard, through the fog to my wood-shed, to get fuel, I suddenly enter a tiny, localised shower of rain. I have to walk under a tall ash tree and this is fog-drip. The vapour in the atmosphere has condensed on the cold twigs of the tree, and is falling as liquid water.

I’ve experienced fog-drip in the past, but last week there was a phenomenon I’d never seen before. The drip off the trees was not liquid

water, but small flakes of solid ice. They fell noisily to the ground, and, soon, every large tree was growing in a glistening circle of white-ice flakes in the surrounding green. In some parts of the world, fog-drip is ecologically important. The ability of trees to condense water from fog or clouds creates the cloud forests of parts of Africa and South America, and some tall oceanic islands.

I’ve been in a fine example on the volcanic peaks of La Gomera, in the Canary Islands. And, once, when I was in the coastal forests on the California/Oregon border, an elderly Native American talked to me about the ecology of the forests. They get very little rainfall, but fogs regularly sweep in from the Pacific and the fog-drip irrigates the forest.

The coastal redwoods are valuable in this respect. They are the tallest trees in the world and their small, scale-like needles offer the largest area for condensation. When loggers arrived and started to selectively fell the redwoods for lumber, many streams dried up. This had a bad impact on a large fish called the steelhead, a sea-run form of the rainbow trout, which had been an important food resource for the Native Americans. It makes a good lesson in ecology, and the complex interactions between living and non-living systems that make life possible on this planet.

So, I’ve been watching to see if there are any local lessons to be learned from the fog. It obviously has an impact on birds and animals, particularly birds, which depend heavily on their eyesight to make a living.

There are sparrowhawks round here that hunt by flying rapidly down the lane, jinking through gaps in the hedgerows, trying to flush out a small bird they can grab in their talons, before it has accelerated up to its full flight speed. They’re doing well, because the fog is giving them a cloak of invisibility, allowing them to get closer to their prey before it flushes.

But the kestrels and buzzards are doing badly. The kestrel hovers 50 to 100 metres in the air to search out mice, shrews, and beetles – but now, it can’t see them on the ground. The buzzard soars even higher, looking for rabbits and rats and its going to be even hungrier on foggy days. Many birds seem bewildered. I’ve even seen some of them flying into solid objects. The rooks call to each other incessantly, trying to keep in touch. And I’m reminded of a time, years ago, when I went for a walk on the bog in a thick fog. The spring migration of swallows was on, and thousands of them were flying less than a metre above the ground, trying to keep in touch with their landmarks.

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