Frozen bog: winter walks at Tyrelis and one February day at Kamanos

Plank 1

Seven hours of light

Around the winter solstice the sun rises over Šiauliai at about nine and sets before four, and at noon it climbs barely ten degrees above the horizon. On the open bog that low light is extraordinary: long blue shadows behind every stunted pine and frost on the heather lit orange for an hour. It also means that a walk which takes two easy hours in June needs planning in December, because the light goes quickly and the forest path back to the bikes gets dark first.

In winter we walk Tyrelis in the late morning at weekends, starting at about ten and aiming to be off the boards by two. Headtorches come along anyway, because one of us once twisted an ankle on the approach path in January and the last half-hour was walked by torchlight. Winter walks are shorter and slower, and involve a surprising amount of standing still with a hot drink, looking at nothing in particular, which we have come to think is rather the point.

Plank 2

What frozen actually means on a raised bog

A raised bog does not freeze the way a lake does. The sphagnum holds so much water, and the snow on top of it insulates so well, that the ground under a crust of snow can stay soft and wet long after the air has been below freezing for weeks. The bog pools freeze from the rim inwards, and often unevenly, and snow lying on thin ice looks exactly like snow lying on moss. Even in a hard January, when the ground in the city rings like iron, the bog is not a place to wander.

That is the one rule we never relax in winter. The boardwalk is the path, even when snow has filled the gaps between the boards and turned everything into a single white field. Tracks leading away from it prove nothing about the ground: a fox weighs a few kilograms and spreads it over four feet. The planks exist to keep people off the moss, and that stays true in January.

Plank 3

Ice on the boards

The more practical danger is the planks themselves. After a thaw and a refreeze they carry a glaze of ice that is almost invisible under a dusting of snow, and a slip on a narrow boardwalk can mean a fall onto the boards, off them, or both. We put strap-on ice grips on before the first plank, take shorter steps than feels natural and keep our hands out of our pockets. Walking poles with the rubber caps off help on the approach path, and stay folded once we are on the boards.

Fresh snow on the boardwalk is the easy case, since it gives grip and shows everyone else's footsteps. The hard case is the week after a February thaw, when the snow has melted and refrozen into ruts along the planks. Those are the days we sometimes turn back at the first long open section and walk the forest paths instead. There is no prize for finishing a boardwalk, and the bog will still be there in a fortnight.

• Strap-on ice grips, fitted before the first plank
• A headtorch each, even for a walk planned to finish by two
• A thermos and something sweet, eaten standing up
• A spare pair of gloves, kept dry in a plastic bag
• Phones charged and carried in an inside pocket, where the cold cannot drain them

Plank 4

Tracks in the snow

Snow turns the bog into a record of who has been there. Along the boardwalk at Tyrelis we find hare tracks almost every time, the long back feet landing in front of the small front ones, and fox tracks in a neat straight line, one print almost on top of the next. Roe deer come out of the forest onto the fringe of the bog, and twice we have found the broad cloven prints of an elk crossing the boardwalk between the pines, which is as close as we have come to seeing one there.

Birds are fewer but easier to see. Great grey shrikes hunt from the tops of the stunted pines, pale grey with a black mask, perched where they can watch the snow. Flocks of redpolls and siskins work through the birches along the fringe, and ravens call overhead. Black grouse sometimes sit in the birch tops in winter, looking far too heavy for the branches. The cranes, of course, are long gone, and the silence where their calls were in April is part of what makes a winter walk feel so still.

Plank 5

One February day at Kamanos

Kamanos is about an hour's drive north-west of Šiauliai and a different scale of place altogether. It is a strict nature reserve, one of the largest and best preserved raised bogs in the country, and most of it is closed to casual visitors. You can walk the marked trail on its fringe and climb the lookout tower, and anything beyond that is arranged in advance with the reserve. We have always found those limits easy to respect, because the view from the tower explains them better than any sign could.

We went on a clear morning in February, with snow over everything and a hard frost. From the tower the bog ran out flat and white to the horizon, with dark islands of pine, the frozen bog lakes showing only as smoother patches in the snow, and not a single track or line anywhere in the middle. Somewhere out there grow dwarf birches, a shrub left over from the end of the last Ice Age that survives in only a few places in Lithuania. We did not see one, and did not need to.