Physics

Lift (data mining)

Aerospace engineering

Foraging

Reynolds number

Lift-induced drag

Mechanics

Biology

Lift-to-drag ratio

Data mining

Engineering

Zero-lift drag coefficient

Lift coefficient

Turbulence

Marine engineering

Ecology

Takeoff

Computer science

Drag

Thrust

Wing

Environmental science

Vortex lift

Nature Communications

The lift that animal wings generate to fly is typically considered a vertical force that supports weight, while drag is considered a horizontal force that opposes thrust. To determine how birds use lift and drag, here we report aerodynamic forces and kinematics of Pacific parrotlets ( Forpus coelestis ) during short, foraging flights. At takeoff they incline their wing stroke plane, which orients lift forward to accelerate and drag upward to support nearly half of their bodyweight. Upon landing, lift is oriented backward to contribute a quarter of the braking force, which reduces the aerodynamic power required to land. Wingbeat power requirements are dominated by downstrokes, while relatively inactive upstrokes cost almost no aerodynamic power. The parrotlets repurpose lift and drag during these flights with lift-to-drag ratios below two. Such low ratios are within range of proto-wings, showing how avian precursors may have relied on drag to take off with flapping wings.

Birds repurpose the role of drag and lift to take off and land