| Increased plumage abrasion caused by a higher rate of preening could break feather barbules, leading to a reduction in plumage condition. |
| That is, the main shaft of the barb, the ramus, has a branching pattern of barbules. |
| The barbs, in turn, may bear barbules which may hook on to the barbules of an adjoining barb. |
| In contrast, a flight feather has narrow barbules which do not cover the barbs. |
| Downy barbs that were initially sampled from the base of these feathers had microscopic characters that consisted of very long barbules. |
| Plumage of glandless birds was in significantly poorer condition, with more missing barbules, than the plumage of control birds with glands. |
