Birds can be classified as local birds (eg. Tetraestas bonasia (hazelhen, pyy) and migrating birds (most of the Finnish birds). There are also intermediate species (eg. Regulus regulus (goldcrest) which do not migrate if conditions are favourable enough for them, or some may migrate only over short distances to Southern Finland. All the local bird species and some intermediate species have special adaptations in their habits, structure and physiology (temperature regulation) to the long cold winters of Finland. The migrating Finnish birds migrate twice a year. During the spring they move to their breeding areas within Finland and during autumn they move away to avoid the cold winter. Birds usually migrate to the same place every year.