How and why do migrating birds flock together in flight?
We often think of migratory flocks as intimate gatherings, but they can equally form because individual birds are travelling in the same direction. Strangers set off instinctively following the same route and they then converge. A group of ducks might simply form a random gathering for a few hours, while geese and cranes fly as families.
Whether strangers or acquaintances, all benefit from the universal advantages of flocking. Keeping together means more eyes to spot approaching predators, shelter or land.
Sociability is also important for the birds that they call to each other constantly. Even unrelated birds will flock together in the name of safety.
The most famous formations are made by swans, geese and waders, which often assume V's or boomerang shapes. These shapes have biological significance for energy saving and on a long journey the formation could be vital to help an individual complete its migration.
Key positions in a geese formation include ;