Adult Alula Feathers Colour: Slate-grey to dark charcoal. Because they sit on the upper leading edge of the wing joint, they match the dark slate-grey plumage of the upper wings and back rather than the pure white of the chest and under-wing coverts.
Texture & Shape: Stiff, narrow, and sharply pointed. They are miniaturised flight feathers designed to withstand high wind resistance when lifted.
Function: They create a small gap that channels airflow smoothly over the wing, allowing the eagle to maintain control when slowing down to snatch fish from the water's surface.
Juvenile Alula Feathers Colour: Mottled dark brown. Juvenile sea-eagles do not develop their grey-and-white adult coloration until they are 4 to 6 years old.
Their alula feathers start dark brown to match their overall immature camouflage.
