Feather structure: typical vaned feather (Figure 1)
Figure 1. Typical vaned feather
Structure of vane: (Figures 2 and 3)
Figure 3. Structure of barbules and hooklets that join them
Feather types:
Vaned feathers: made up of parts shown above. May have aftershaft, especially on contour feathers
Semiplumes: have rachis, barbules lack hooklets; insulation, buoyancy in water birds
Filoplumes: may have small or no vane; associated with contour feathers; sensory function (associated with nerve endings in skin); display function
Bristles: lack vane, stiffened rachis. Occur around mouth (rictal bristles), eyes (eyelashes), nostrils; protect eyes, nostrils; enlarge gape
Powder downs; barbs at tips disintegrate continuously to produce powder; occur in some water birds; helps waterproof feathers
Feather location on the body: (Figure 4)
Figure 4. Location of pterylae and apteria on dorsal (back) surface of a typical bird
Some feather specializations:
| Molt | Definition | Plumage resulting from molt |
| Prejuvenal molt | loss of initial down; growth of first vaned feathers | Juvenal plumage: typically cryptic |
| First prebasic molt | loss of juvenal plumage; growth of feathers that typically last through first non-breeding season. In typical temperate migratory species, occurs in fall before first migration | Basic plumage 1: often cryptic |
| Prealternate 1 | loss of first basic plumage; growth of feathers that function in courtship. In typical temperate species, occurs in spring before first breeding effort | Alternate plumage 1: typically brightly colored |
| Prebasic 2 | loss of alternate plumage 1; growth of typical feathers functional in non-breeding season. In typical temperate species, occurs in fall, after breeding, before migration | Basic plumage 2: often cryptic |
| Prealternate 2 | loss of basic 2; growth of feathers that function in courtship. In typical temperate species, occurs in spring before second breeding effort | Alternate plumage 2: typically brightly colored; may be brighter than alternate 1 |