In the quiet of late winter, tracks in the snow across Rahesuo and Valkeasuo peatlands reveal the hidden movements of wildlife. This field survey offers insight into how species survive the coldest months and how restoration in the Koitajoki Watershed is supporting boreal ecosystems.
In the Koitajoki Watershed, Finland, restoration focuses on reconnecting habitats and recovering the natural function of peatlands, forests and rivers. Monitoring plays a key role in this work, helping to track how species respond across seasons and in restored areas. Winter surveys are particularly valuable, as tracks in the snow provide clear evidence of species presence, behaviour and survival in remote peatland landscapes.
This blog was written by Tiina Oinonen, Monitoring Lead for the Koitajoki Watershed project, who shares insights from a mid-winter snow track survey in the Rahesuo and Valkeasuo peatlands.
Reading the winter landscape
The deepest winter usually feels quiet, when nature is in a resting state, trying to survive the coldest and darkest period. However, some animals are well adapted to winter in the boreal region, and even though they are very good at avoiding human contact, we can read their tracks in the snow like recent diary notes.
A mid-March skiing trip to Rahesuo and Valkeasuo peatlands resulted in four bird species and five mammals. Three grouse species, capercaillie, black grouse and willow ptarmigan, were identified from droppings, footprints and night burrows. We also observed ptarmigan directly at both sites. The fourth bird species was parrot crossbill, feeding on pinecone seeds of old pine. Mammals identified from tracks included moose, red fox, lynx, marten and mountain hare.
Tracking willow ptarmigan through winter
One of the most important adaptations to cold winter conditions is avoiding heat loss. One of the most interesting species is the willow ptarmigan (Lagopus lagopus), a territorial bird that lives in the same area in both summer and winter. During bird monitoring in the nesting season, a few nesting pairs have been observed at both sites, in open pristine areas as well as in recently restored parts. Snow tracking helps us to estimate their survival over the winter.
Ptarmigan are adapted to snow and low temperatures with an insulating coat of feathers, and even their feet are covered. This reduces heat loss and allows them to move on top of the snow without sinking, making their tracks easy to identify. By following these tracks, we can also observe their winter diet, which includes at least dwarf birch (Betula nana) and blueberry (Vaccinium myrtilloides) buds. Dwarf birch is common on peatland ridges, while blueberry grows on mineral soil islands and in the marginal forests of these peatlands.
Surviving cold nights
To avoid heat loss during winter nights, ptarmigan roost in the snow, which is an efficient insulating material. At both sites, we detected clusters of night burrows, with six to eight burrows close to each other, along with droppings. A group of birds has likely spent the night there together, which may also help reduce the risk of predation.
We also studied snow layer quality in Valkeasuo during the winter and found that temperatures were up to 13°C warmer under the snow layer in late February, when there were 31 to 33 cm of powdery snow. This insulating effect diminished when a spring warm period turned the snow into slush.
Changing snow conditions and risk
Ptarmigan also moult their feathers, turning white for winter and reddish-brown for summer, to stay camouflaged from predators. The normal 30-year average snow depth at the nearest measurement station is between 79 and 81 cm in mid to late March. This is the second consecutive winter with lower snow depth in the region. We measured a maximum of 43 cm in a treeless area of Valkeasuo on 10 March, and by 23 March the snow had almost melted.
Long-term averages show that snow usually melts between late April and mid-May, which is when ptarmigan typically change to their summer plumage. This year, earlier snow melt may leave ptarmigan exposed while still in white plumage, increasing their risk from predators.
This blog was written by Tiina Oinonen, Monitoring Lead for the Koitajoki Watershed project. To find out more about the Koitajoki Watershed, visit their project page.
