Country diary: disoriented birds can no longer tell day from light-polluted night

Derek Niemann
Photograph: Carl Morrow/Alamy Stock Photo

A good hour before sunrise, two song thrushes were in full voice in a small copse by the railway line. A little burst of this, a little snatch of that. What stirred them into pouring out attention-seeking nocturnes now? This was a time when tawny owl talons might be reaching for their last supper of the night.

Out to the west, false dawn had begun at dusk the day before. The town’s street lamps, the glow-worms of winter, had fired the sky with a luminosity like dying embers. A far greater stimulus came from four blazing moons at the birds’ backs. A bank of security beams from the yard of an industrial estate whitened the trees, seeped into the hedgerow and lit the pale grass of the neighbouring field.

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This illuminated landscape was one of disorientating contrasts, the spotlights exposing every feature facing the factory to their remorseless glare, while all else was lost in deep shade. I stood before a stumpy tree that still held many of its leaves, curled like crinkled baubles. I could not fathom its species by vision alone in this bewildering chiaroscuro world, though I guessed at sycamore. This was an environment that mixed certainty and hunches.

A few hundred metres on, I escaped into the comforting evenness of semi-darkness, where I could see that I couldn’t see. Thrush song sprinkled gently from far behind, and I looked back to find that distance had shrunk the harsh flares of the industrial estate to pinprick spots. The distraction broke my concentration; no sooner had I turned back than a teasel head came up at my thigh, taking hold with a disturbing animal-like force, tugging at my trouser leg, angrily insistent.

Out to the east, colourful stars shone still at the end of this cloudy night, a vertical column of four reddish-orange lights rising above the wooded ridge. I joined the dots unthinkingly. These lights part-delineated the 244-metre-high mast of the Sandy Heath transmitter, a beacon for three counties, one that could be seen for 20 miles around. Would a migrating bird be lured by these guiding stars? Or could it recognise fakes in the dark?