THE ringing yodel of a green woodpecker carries across the trees here in Dollar Glen.

It is a call that is surely the furthest reaching of any Scottish bird, having a certain pitch and strength of delivery that pierces the air like a dagger.

I couldn’t see the bird because of the dense greenery, which was a shame because these woodpeckers are stunning birds with their bright green body plumage and scarlet head-cap.

Despite being a woodpecker, they spend a considerable amount of time on the ground in open areas, feeding on ants in particular.

The steep scarp of the Ochils is perfect for them, thanks to its mix of trees and open ground where the sun-catching southerly aspect allows insects to thrive.

I stop for a while by a deep, moss-covered cleft at the bottom of the glen. It was just like being in a temperate rainforest; a moisture laden environment rich in ferns, mosses and liverworts.

Here, I find the strange shiny and elongated leaves of hart’s-tongue fern, while the frilly fronds of hard shield ferns decorate the mossy trunks of some of the trees.

Down by a ledge close to the tumbling burn, the rocky sides are covered in a creeping mat of liverworts, simple plants that thrive in the humidity and shade.

Like many other Ochil glens, the deeply incised south-facing Dollar Glen, with its gorges and steep flanks, is well protected from prevailing westerlies and cold easterlies, and as such, features a mild and humid micro-climate where unusual plants can prosper.

It is also a glen that holds many oak trees, which adds to this wonderful diversity. A single oak here can harbour hundreds of different insect species, plus a host of other invertebrates, along with mosses and lichens.

Thus, each tree in this little Ochil glen is like a little world in its own right, a special place teeming with life and where undiscovered natural secrets still lie hidden within their green embrace.