This wisp above the canopy appears to be a water vapour trail - a little cloud.
This wisp above the canopy appears to be a water vapour trail – a little cloud.

So, this is a little weird. A colleague and I were on the road north of Shepparton at 0930 a few weeks ago, when we noticed these little chimneys of ‘gas’ above the canopies of the roadside Grey Box trees (Eucalyptus microcarpa).

At first unable to grasp what on earth we were seeing, we stopped for a closer look.

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These little vapour-trails were on the lee side of the canopy and showed the direction of the light breeze blowing at the time. I can only guess that it’s condensed water vapour, trapped in a sort of slip-stream on the lee side of the tree and in the shade of the canopy – making them seem dark. It was a sunny, cool Autumn morning.

But what’s making the water condense and why at specific points and not all over the lee sides of the trees?

And now for a closer, though grainier, look. One reader comment, below, suggested they might in fact be bees. I’m not convinced, but neither do I have a better explanation.