Pigeons Make Flight Plans

Though their head-bobbing walk may be comical, pigeons in flight are no fools. They’re urban artful dodgers, threading their way among buildings and other obstacles. David Williams and his Harvard University colleagues studied the birds’ maneuvers to learn how they avoid collisions.
First Williams trained wild pigeons to fly through an empty corridor. Then he placed vertical poles at intervals in the corridor and videotaped the birds in the altered course. He expected them to use one evasive move consistently. Instead, the birds employed two moves, which researchers named: a “pause,” in which the wings stalled at the top of a stroke, and a “fold,” in which the wings were pulled back. Pausing was better for efficiently maintaining height, the study found, while folding
helped the birds fit through narrow gaps and remain stable in a collision. — Lindsay N. Smith

 source: National Geographic - October 2015