Any of the minute hooked filaments that interlock the barbules of a bird's feathers.
- ‘It is important for the feathers to be relatively broad, with a web of good firm texture, a strong shaft, the barbs, barbules, and barbicels closely and tightly knitted together.’
- ‘Often part of a bird's incessant cleaning routine is the straightening of wing primaries, which seems to help reattatch the barbicels so the wings remain fully functional.’
- ‘Two sets of barbules branch off from each barb and interlocked by means of tinier barbicels to give the feather great strength and smoothness.’
- ‘Along the edge of the barb are numerous barbicels, we refer to them as Velcro hooks.’
- ‘Barbs can be separated from each other and smoothed back into place because barbules and barbicels act somewhat like a zipper.’