In stage three, the barbs partially unite to form a central rachis, and even smaller filaments called barbules start to branch off from the barbs. (discovermagazine.com)
When light strikes a superblack feather's forest of barbules — which tilt at about 30 degrees toward the outer tip of the feather — it gets reflected into cavities between the tiny structures rather than outward, McCoy says. (scientificamerican.com)
The cork - screw shaped structures in this slide are the tightly coiled bases of feather barbules. (seeker.com)