Secondary flight

feathers

The secondaries give

the wing its ‘foil’ shape

to provide lift. Along

with the retrices – tail

feathers – these help

the bird to steer and

control its speed.

Covert feathers

These feathers grow

in rows lying on top of

each other like roof

tiles to help streamline

the bird, improving

airflow over the wing.

Slots

The slots are created

when the primaries are

separated. These can

be used to channel air

from below the wing.

Vortices of turbulent air

that contribute to drag

can be controlled and

used to provide extra lift

when the bird feeds that

air through the slots.