What is an alula?

Birds have an alula on each wing. 

An alula is a small projection – like a human thumb – on the edge of a bird’s wing. It means ‘winglet’ or small wing.

An alula is a free-moving digit that has 3-5 flight feathers on it, depending upon the species of the bird. It also has covert feathers overlapping the flight feathers.

It is difficult to see because it lies flat against the wing. It lifts up to help a bird to fly at slow speeds and to land. A bird moves its alula upwards and forwards to create an angle to slow down the flight, without stalling.

An alula is similar to the slats on a plane’s wing that lifts up when the plane is landing, and lies flat when the plane is in flight.

Photographer: Martina Nicolls

Martina Nicolls: SIMILAR BUT DIFFERENT IN THE ANIMAL KINGDOM