Pinion

The left is possibly a pinion

Primaries [bird feathers]

Primaries are connected to the manus (the bird's "hand", composed of carpometacarpus and phalanges); these are the longest and narrowest of the remiges (particularly those attached to the phalanges), and they can be individually rotated. These feathers are especially important for flapping flight, as they are the principal source of thrust, moving the bird forward through the air. Most thrust is generated on the downstroke of flapping flight. However, on the upstroke (when the bird often draws its wing in close to its body), the primaries are separated and rotated, reducing air resistance while still helping to provide some thrust.^[4] The flexibility of the remiges on the wingtips of large soaring birds also allows for the spreading of those feathers, which helps to reduce the creation of wingtip vortices, thereby reducing drag.^[5]

Bald Eagle (Haliaeetus leucocephalus) in flight with primaries spread to decrease drag and improve lift

The outermost primaries—those connected to the phalanges—are sometimes known as pinions.