Where: Scandinavian birds migrate to Western and Central Europe, some as far as the Mediterranean.
When: migration takes place in October and November, with a return in March and April.
Irruptive pattern: the proportion that stays or passes through is governed by the northern berry crops — in some winters the species is numerous in the south, in others scarce.
The passage: migration takes place mostly by day in loosely knit flocks, and in good berry winters some birds may stay well to the north instead of moving on southward.