We have seen that long arms mean greater wing area, which is useful for generating lift and thrust.

But let’s take a closer look at the motion of the wings.

Notice that the bird does not just flap its wings up and down.

The flight stroke has a more complex motion that allows the bird to generate both lift and thrust with its wings.

The flight stroke is possible because the shoulder socket and wrist allow a large range of motion.

Click on the shoulder socket to begin exploring this feature.