Family ties remain strong during the autumn migration; the adult male and female keep together with their young for the entire journey. During winter, the young become increasingly independent. Family ties are weakened and completely broken by the time of the spring migration.
The return trip north begins in February. The two routes over Sweden are again followed. Near Lake Hornborgasjön up to 20 000 cranes may now gather at one time.
As the cranes continue northward, the flocks thin out as they pass appropriate nesting areas. The last cranes continue on to their nesting areas in isolated marshes of northern Norrland.
Cranes do not become sexually mature until they are three or four years old. Younger, immature birds spend the summer together in flocks at sites near lakes and sea inlets where food is abundant.