How do birds slow down in flight

Flight techniques: why birds don't bump everywhere in flight

Many animals, in certain situations, use various types of movement to help them overcome obstacles. Birds also have a multitude of flight techniques that are used to maneuver in tight spaces - for example when building nests in trees, when foraging for food, when hunting or when fleeing. The choice of the specific flight technique depending on the situation and size of the obstacle has been largely unexplored to this day.

The US biologists David Williams and Andrew Biewener of Harvard University wondered how birds, for example, can fly through a forest at high speed without colliding with the trees, branches and twigs.

To do this, they researched the flight techniques of rock pigeons (Columba livia)who were faced with an obstacle in a 24 meter long flight tunnel. This consisted of vertical poles, which, like a fence, stood at a distance of 13 to 26 centimeters from each other.

For comparison: the wingspan of a pigeon is on average 64 centimeters. The researchers observed how the animal maneuvered through the bottlenecks despite its size.

Two stereotypical wing positions observed

They would have expected a very special flight strategy, write the scientists in the journal "Proceedings of the National Academy of Sciences" ("PNAS"). Instead, they observed two very stereotypical wing positions that were used depending on the distance between the bars:

The first position was achieved by folding the wings over the head in the upstroke. After the bottleneck was flown through, the animals resumed flapping their wings. In the second flight technique, the wings were placed close to the body in flight, i.e. paused until the obstacle was overcome.