Here's a question for a mid-afternoon daydream: if you suddenly found yourself stranded in Scottish woodland in January, could you find anything to eat?

Now, you might assume, as I did, that the answer would be no. However, going out for a walk with Patrick McGlinchey of Backwoods Survival School, based in Cambuslang, I soon learn differently.

The best place to seek food in winter is coastal areas. The sea provides fish, crustaceans and seaweed all year round. However, to test our foraging skills, we stick to the central belt, visiting woodland near Blantyre which has reclaimed a long abandoned railway bed.

Immediately we find a hawthorn still bearing many haws and McGlinchey urges me to try the creamy, slightly gritty, white flesh, adding that the young spring leaves are also edible.

If you spend a few hours collecting the berries, he says, they can be seeded, boiled together and rolled out to make "leather", a chewy, flat panel of dried fruit.

A few feet further into the forest, we find the first signs of spring, wild garlic bulbs poking through the leaf mulch. Nearby are some windfall crab apples and, on a grassy slope outside the wood, some young sorrel leaves with the acidic tang of rhubarb. McGlinchey also spots a tall, unremarkable-looking shrub called cat's tail. To a hungry traveller in the know, spotting that would be like seeing an oasis in a desert, because it has long, carbohydrate-rich roots which could keep you going for two days.

Backwoods' aim is to teach students how to thrive outdoors as ancient Scots did. McGlinchey is passionate about teaching others how our ancestors survived in our often damp and cold, but highly productive, landscape. As well as teaching foraging skills, the former artist also offers instruction in backwoods crafts, such as making ropes and baskets from natural fibres, tools from bone, and clothes and shoes from tanned buckskin.

As we walk, I point out a huge mushroom sticking out of a birch tree. "Ah yes," says McGlinchey, "that's an birch polypore (piptoporus betulinus)."

It can't be eaten, he explains, but has many other uses: cut a rectangular strip from the underside, and it makes a padded insole for a shoe. Bind a piece on to a wound and it provides an absorbent natural plaster. You can also sharpen your knife or razor on the upper surface (it's also known as the razor strop). Dig a wee pit in it, place a glowing ember inside and cover, and it will slow-burn for 10 hours, ready when you want to make a fire for dinner.

Suddenly, every shrub, fungus, and tree ceases to be part of the backdrop and takes on a vital identity of its own.

"The birch," says McGlinchey, passing his hand over the smooth bark almost reverentially, "is the first tree I would come to in the forest."

The cambium layer just below the papery outer bark is a "famine food" which can be soaked or roasted then ground into a gruel. The tough bark can be used to make vessels in which to store things (when heated it becomes malleable and cools into the desired shape). Then there's the resin, a thick tarry oil which was used in the past to waterproof clothing and canoes.

Due to the bark's high oil content, it's also good for lighting fires in wet weather. Birch makes good bow drills, ancient and highly effective fire-making kits.

I get to see one of these in action when we stop to make a fire, although I don't rate our chances of getting a blaze going. It's raining, for a start, throwing down big, fat, relentless droplets that are barely impeded by the leafless trees, and the ground is completely saturated. McGlinchey has collected skinny boughs from dead trees and stripped them of their bark, but they are still damp. I'm sceptical that we'll build a warming fire using such soggy materials. Oh, me of little faith.

McGlinchey takes out his fire kit, which has one ruler-shaped piece of wood with little wells carved into it (the hearthboard), a long spindle, bow and bearing block. He places the tip of the vertical spindle into one of the wells, over a handful of bone-dry lichen and leaves, and rotates the spindle briskly between his palms until smoke starts to rise from its base. Holding up the lichen and leaves, he blows into it and within seconds it has caught fire spectacularly. We place it on our bed of sticks, the uppermost stripped of bark and cut into feather-thin strips sliced from the wood's dry core, and soon have a good fire going and the kettle on.

The next hour is lost in chat and reminiscence, and what McGlinchey calls "reconnecting" with an ancient pace, and way, of life. He has an endless store of tales from his survival expeditions in remote Canada, Borneo and elsewhere. This ritual, of sharing stories while staring at the mesmerising flames is one that countless generations of humans built their lives around and, for a short while, transforms a pocket of wilderness amid the A-roads and housing estates of central Scotland into a portal to the past.

The Backwoodsman course, Friday-Sunday, teaching the core skills of fire, food, shelter and water, costs £160. One-day courses are also available. Please contact the school to discuss. Other extended courses include Native Paths, Backwoods Crafts and Buckskin Tanning.