Ever wonder when you hear or read someone mention the term “primary feathers”. First thing that comes to my mind is the outer most feathers of the wing. If that is what you were thinking, go ahead and take some money out of petty cash and buy yourself lunch because that is right. I direct you to a cool little document that us tax paying US citizens paid to create. “Wing Feathers” is produced by the US Fish and Wildlife Service and it is apply named. Every bird has nine or ten primary feathers on the furthest edge of the wing. They are attached to the bones of the “hand”. Yup-birds have hands, fingers, and even a couple of thumbs, but they have feathers attached to them. In addition to the primaries birds also have up to 25 secondary feathers attached to the fore arm and a small cluster of feathers called “alula” attached to the thumb bone.
Each primary feather is assigned a number with the highest being the tip. Each of these feathers has a different shape and length. Primaries can also vary in shape between bird type. For example soaring birds have different shapes then say a song bird. The shape is tailored to the needs of the bird. According to the USF&G document:
“In large soaring birds, the outer primaries have elongated narrow tips formed by a notch in the posterior (trailing) vane and emargination in the anterior (leading) vane. This produces the characteristic fingers visible at the end of the wings in a soaring bird. The elongated tips provide slots that increase lift as air is forced through the narrow gaps.”
I used to think that a wing was made up of hundreds of feathers but as you can see the are no more than 35 functional ones with the small cluster. It is more simple yet more functional than I previously thought. I always believed that most of the flight variables like lift and turning was controlled by motion of the wings but as you can see the actual shape and formation of the feathers has a lot of input. Imagine if you had feathers attached to your fore arms, hands, and fingers. I think you would need about a 40-50 foot wingspan to have a shot at achieving flight.
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