Some migrant birds are already flocking to the north, but a cold snap may delay more returns.

Climate change and ice-free Arctic seas are contributing to milder temperatures in Finland.

Flocks of whooper swans have been grazing in a field in southwestern Finland, although these swans don't typically return to Finland until March or April, according to Finland’s environment administration.

The golden plover and other species are moving their arrival time up by an average of half a day per year, and have been doing so for the last 20 years.

Unusually mild weather and foggy mornings have caused many migratory birds to delay their departure south, according to Birdlife Finland.