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10th January 2019 - The wonder of flock formations

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 ;

  • The leader - This position is not fixed throughout the flight and can change.  It is not known how leaders are chosen in the formation.
  • The following bird - The following bird gains from using upward-moving air generated from the bird in front, this is called the 'upwash'.
  • Mid position - in the middle of the formation, each bird positions and spaces itself perfectly to gain the most uplift and maximum energy saving.
  • The final bird - Birds don't follow the Vs perfectly and do make errors.  Its hardest being at the back!