The opposite of the rachis is the calamus, which anchors the feather to the body and is moved by attached dermal muscles.
It's possible that the feathers assisted the dinosaurs running up inclines, and this advantage of speed eventually lead to flight.
[2] Their plumage patterns and bold coloration were to attract the opposite sex, not unlike modern birds today.
Using new technology to analyze well-preserved melanosomes, scientists can reconstruct what the feathers on fossilized dinosaurs would have looked like, revealing some to be rather flamboyant.
More recent efforts to explain the original purpose for feathers involve multiple of these theories in combination.
Ken Dial, a flight researcher at the University of Montana-Missoula, shows how chicks often use their feathers by flapping their wings to aid in navigating inclined terrain.
Similarly, the pulp caps, which protect the dermal core, also fall off as the feather grows.
The main feather tissues later unfurl, which causes the disposal of the sheath and the pulp caps as it assumes its functional shape.
As the feather grows, its spathe, which is where the rachis and vanes attach, continues to form.
The calamus is the quill of the feather, which is the bottom portion that stays mainly within the pulp cavity.
From there, the feather is fully developed and will remain as such until molting occurs, causing it to fall off.
Feathers fall off during molting, which occurs at different times through the year depending on the type of bird.
In general, they are long and asymmetrical with a thin leading edge allowing for strong stable feathers during flight.
Flight feathers are connected to the bone with ligaments allowing them to be moved with precision and ensuring they remain tightly attached to the bird.
The primaries are at the far (wrist) end of the wing and provide forward thrust during takeoff and flight.
The secondaries are in the middle of the wing and attach to the ulna and form an airfoil which provides lift.
Whereas, the ostrich utilizes its feathers for mating and for fluffing, which allows them to release heat and cool down.