Molting Season

This is the time of year we start getting calls from customers describing scraggly looking birds in their yards. Many of the birds are infested with mites and have lost their head feathers; others’ feathers are just worn out from all the trips back and forth this summer feeding hungry babies. But, whatever the reason, all the missing feathers will grow back during the bird’s annual fall molt.
All birds go through at least one complete molt each year: all feathers drop out and new ones grow in. Feathers do not drop out at random but in a symmetrical pattern consistent within each species. The main function of the annual molt is to replace old, worn feathers.
Feathers make up about 4-12% of a bird’s total weight; growing a new set uses up a tremendous amount of energy. Most complete molts, triggered by length of day and hormones, take place in late summer or early fall when food is plentiful. The fall molt ensures a fully grown, new set of flight feathers for the migrating species—warblers, hummingbirds, orioles, etc. For birds that winter over—chickadees, titmice, woodpeckers, cardinals—this molt adds downy, insulating feathers for warmth. Many species also undergo a partial molt just before breeding season. The American Goldfinch is a great example: the male changes into brilliant yellow courtship plumage in early spring.
Periodic molting ensures a bird’s feathers are in tip-top shape: for flight, for insulation and for courtship.