Ornithology term
Molt
Also: moult, feather replacement
Definition
The regular process of shedding and replacing feathers, often producing a recognizable change in plumage.
Why it matters in the field
Molt explains seasonal changes that can make a familiar bird look unfamiliar. Patchy feathers or a shift between breeding and nonbreeding plumage can be interpreted alongside age and season.
Examples
- An American Goldfinch replaces bright breeding feathers with a duller nonbreeding plumage after nesting.
- A growing feather enclosed in a sheath is part of feather replacement and may be visible during active molt.
Common confusion
Molt is normal feather replacement, while feather loss can also result from wear, injury, parasites, or abnormal development. A photograph may not reveal the cause.
Observation notes
Photograph both sides when possible and record the date, since molt progresses across feather tracts and may look uneven. Look for growing feathers, symmetrical gaps, worn retained feathers, or a boundary between feather generations. These signs can support a molt interpretation, but observers should avoid diagnosing disease from appearance alone.
Identification during molt should lean more heavily on structure, voice, behavior, and unchanged feather regions. Compare the bird with age-specific and seasonal references rather than only a breeding-plumage portrait. If a bird cannot fly, shows an open wound, or remains in immediate danger, contact a licensed wildlife rehabilitator instead of treating ordinary molt as the only explanation.
Molt terminology can become technical because complete, partial, prealternate, and prebasic cycles describe different replacement strategies. Beginners can start by recording which feather regions look fresh, worn, missing, or growing. Use a species-specific reference before naming a molt stage, since timing and sequence differ and broad seasonal rules have many exceptions.
Word origin
From an Old English root associated with changing or casting off.