The Flight Feathers of Birds

Feathers are a unique characteristic of birds and are a key requirement for flight. Feathers are arranged in a precise pattern over the wing. When the bird takes to the air, its wing feathers spread to create an aerodynamic surface. When the bird lands, feathers are flexible enough in their arrangement to enable the wing to fold neatly against the bird's body without bending or damaging the flight feathers.

Flight Feathers

The following feathers make up the typical bird's wing:

• Primaries: Elongated flight feathers that grow out from the end of the wings (the 'hand' area of the wing). Birds typically have 9-10 primaries.
• Secondaries: Long flight feathers positioned just behind the primaries and grow out from the 'forearm' area of the wing. Many birds have six secondary feathers.
• Tertials: Three flight feathers that are closest to the bird's body along the wing, located next to the secondaries.
• Remiges: A term used to refer to primaries, secondaries, and tertials together.
• Greater primary coverts: Feathers that overlap the base of the primaries.
• Greater secondary coverts: Feathers that overlap the base of the secondaries.
• Median secondary coverts: Feathers that overlap the base of the greater secondary coverts.
• Lesser secondary coverts: Feathers that overlap the base of the median secondary coverts.
• Alula: The feathers that grow from the 'thumb' area of the wing on the leading edge of the wing.
• Primary projection: The section of the primaries that, when the wing is folded, project beyond the tips of the tertials and sit at an angle towards the tail.
• Underwing coverts: Located on the underside of the wing, underwing coverts create a lining at the base of the flight feathers.
• Auxiliaries: Also located on the underside of the wing, the auxiliaries cover the 'armpit' area of the bird's wing, smoothing the area where the wing meets the body.

Reference

• Sibley, D.A. 2002. Sibley's Birding Basics. New York: Alfred A. Knopf