The cost of flight in flocks

Abstract

There are well-known aerodynamic and energetic benefits to flying in an orderly formation. By contrast, it seems that the flocking flight seen in pigeons is metabolically expensive. So why do they do it? See Letter p.494 Close monitoring of 18 pigeons during 7 bouts of flight around their home loft, in which they clocked up more than 9 pigeon-hours and 400 pigeon-kilometres of flight, suggests that there is a high cost involved in formation flying. Pigeons in flocks flap much faster and engage in banked turns that double g-force and quadruple effort. Flying close together is, in terms of energetics, very costly. Whatever advantage flocking provides must lie elsewhere.