Wing bars—also known as alular feathers, bastard wings, or false wings—are feathers on the leading edge of a bird's wing at the bend of the wrist. They are highly variable in structure and function and may be reduced, missing, or fused to primary coverts.
These feathers enable birds to:
Enhance agility and maneuverability: Wing bars create vortices that generate lift and increase stability, especially at low speeds and during quick direction changes.
Improve gliding efficiency: They smooth airflow over the wing, reducing drag for more efficient gliding.
Assist during landing and take-off: Wing bars create additional drag when wings are partially spread, providing lift during take-off and stability during landing.
Non-flight functions: In some species, wing bars may serve communication, courtship, sensory, or camouflage purposes.
The presence and features of wing bars vary among species based on flight requirements and ecological niches.