his valley is one of the greenest places in England I know, partly because it’s so steeped in shadow – a result of the high limestone cliffs that rise to the south. Currently the sun climbs only to the lip, leaving the dale bottom chilled and still. Yet even in this dormant leafless state it feels like temperate rainforest. The river flows with the sort of dense water that runs from a drake mallard’s malachite head, like oil off a skillet. Every tree and stone is furred in moss or feathered with hard fern, but just beneath the cliff’s horizon, among the treetops, is an inner membrane of song thrush song that seals in the dale with its warming, bell-like timbre. By one of the bridges, two dippers have built a nest: a football-sized ball of moss layered with a sense of time and season. It’s anchored on a smear of liverwort, atop a gritstone block, which was hand-chiseled by 19th-century workmen from rock that is 260m years old. Now the dippers are laying inside the dome a lining of old beech leaves which are dunked, one at a time, to anoint them with the sacred element. Water. The males’ song even has a riverine shape, lacking any sense of beginning or end, and is added to the Wye’s wider flow. His plumage is almost all dark, befitting the dale’s recessed gloom; yet he has features that shine like splashing water: a snowy breast, stout legs with metallic sheen and eyelids that flash white whenever he blinks. He blinks every five seconds. Just as dippers are birds of two elements, they seem creatures of two characters. One is infinitely nervous. Standing midstream, they sweep the body left and right while flexing their tarsi so that they bob and swivel perpetually. Throughout, the eyes blink white, and sometimes you see a bird poised for action as if it were consciously subduing these involuntary tics before advancing to more meaningful action. Then it will fling itself fiercely into cold water and surface and dive with electric seal-like elan. Suddenly it spears back into mid-air, possesses a bankside stone and bursts into song. Then it stops, bobs, swivels and blinks, readying itself for more action.