The Common Crane (Grus grus) is gregarious for most of the year. It seeks the company of its kind on all occasions, whether it be large gatherings prior to migration, migratory flights, or during wintering. Groups of several hundred to several thousand members are not uncommon. Smaller groups are often travellers on their way to join the main flock. If you see solitary ones, it is likely that they are ill, forced to abandon their travelling companions.