Animals Warmer winters have made it easier for birds to overwinter, but some species are affected by snowlessness

The number of wintering birds in Finland has increased. The warm early winter and the frosts that come quickly in the middle of winter are a difficult combination for many birds.

In Finland the number of wintering birds has increased greatly in the 21st century as winters warm. The number of wintering waterfowl in particular has multiplied in a short period of time, as the coast and archipelago now remain ice-free even through winter.

Warming has been of great benefit to birds, as warm winters provide better food and use less energy for heat production. Bird mortality is always highest during periods of severe frost, says conservation expert at Birdlife Finland Tero Toivanen.

“In general, mild winters that do not involve large temperature fluctuations are the easiest for birds,” Toivanen describes.

Warm However, early winter and frosts that come quickly in the middle of winter – that is, a fairly typical Finnish winter today – can be difficult for many birds trying to overwinter in Finland. In the warm autumn and early winter, there are many birds in Finland that do not tolerate harsh conditions.

Wintering near the nesting area would still be an advantage for the birds if they succeed, because then they will avoid the dangers and stress of the migration and will be the first to choose a suitable territory in the spring.

“If the cold weather comes right from the beginning of winter, the migratory birds know how to move in time and are in good enough condition for the trip. On the other hand, a long winter is a burden on birds living in Finland all year round, ”says Toivanen.

Birds that have adapted to the traditional cold winter may be disadvantaged by warmer winter winters. For example, in winter, a white-tailed plover suffers from snowlessness because then its white protective color does not work and the risk of being caught increases. Chicken birds are also affected by low snowfall during severe frosts, as they do not get into the snowdrift, ie sheltered from the cold under the snow.

Toivanen points out that, in addition to the weather, the amount of food greatly affects how many birds overwinter in Finland. For example, tree seed yields and berries are important.

“Birds that depend on the berry and seed crop can move for food: when food is scarce, they often spend the winter outside Finland.

According to Toivanen, heavy snowy winters are difficult to obtain food for birds of prey, such as the owl. The survival of birds of prey over the winter depends heavily on mole populations.

Temperatures on both sides of the zero can also make it difficult for birds to get food. When the surface of a tree suddenly freezes, it is difficult for small birds to gain access to wintering insects or winter storages.

Winter feeding helps many birds survive the winter. According to Toivanen, it would be good to take a few things into account when feeding. Feeding should only be started when the night frosts are regular and the migratory birds have largely disappeared. Once started, it would be a good idea to continue feeding throughout the winter until temperatures rise.

“The cleanliness of the feeding place should also be taken care of so that diseases do not spread,” says Toivanen.

The winter population of tufted ducks has decreased significantly during the 21st century.

High-energy food helps birds withstand even severe frosts, and birds that have had enough food during the winter are in better shape in the spring when nesting season arrives. Winter birds especially taste sunflower seeds, peanuts and tallow.

In Finland about a hundred species of birds regularly overwinter. The exact figure is difficult to estimate, as the amounts vary from year to year.

Regional differences are large: much more birds winter in southern Finland than in Lapland, says the chairman of the Central Finland Ornithological Society and a postdoctoral researcher at the University of Jyväskylä Ossi Nokelainen.

“Due to global warming, many partial migrants and procrastinators can be met in the early winter, which is not detected later in the winter. Correspondingly, the first spring migrants can arrive on the coast as early as the end of February, if the snow situation allows early spring migration to begin, ”says Nokelainen.

According to Nokelainen, the tit tit, the tit tit, the viper, the little sparrow and the yellow locust are the most typical guests in winter feeding places near the settlement. In wooded areas, on the other hand, you can come across, for example, woodpeckers, owls and poultry, regardless of the season. In northern Finland, only the more hardened species usually overwinter, of which the usual feeding guests are, for example, the Lapwing and the woodpecker.

Tero Toivanen from Birdlife says that in addition to global warming, winter feeding of birds has also helped some species, such as blackbirds and thumbs, to become more abundant.

According to Toivanen, there are also declining winter birds in Finland. For example, the winter population of dwarfs and moths living in Finnish forests has more than halved during the 21st century. According to Toivanen, the most probable reason for this is forestry: these species need a sufficiently large forest to find winter food.

Other declining, familiar winter birds in Finland include the magpie and the sparrow.

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