Molt is a routine loss and replacement of feathers that can occur at any time of year, but in most birds a complete molt occurs in late summer and fall. For some species a partial molt often occurs in early spring. Timing of molt is important. In late summer and fall, weather is warm and there is generally an abundance of insects, seeds, and fruit that provides energy for molt.
This molt provides birds with fresh plumage -- often colors and patterns that help conceal it in winter environments. It is also a molt in juvenile birds that provides for the transition from dependent juvenile to independent adult. Once the new adult plumage is evident, juveniles must establish a territory of their own.
In spring longer and warmer days result in an increase in insects and the presence of some fruit that provides the energy needed for molt and courtship. This partial molt usually occurs in late March in Florida – and provides birds with their breeding plumage and colors. In some birds, the summer-fall molt results in feathers that have edges that obscure the brighter colors. As those feathers wear through the winter, the brighter colors of their “breeding plumage” are revealed.
In a few birds, molt can occur at any time of year and can be restricted to specific feathers. For example Anhingas have an unusual molt pattern in that they periodically lose all of their wing feathers at once – leaving them flightless – which is not a problem for them since they are intimately linked to water to capture the fish they eat. This pattern, however, requires the presence of trees that they can climb easily for roosting and from which they can simply drop into the water to search for food.
Late summer is a good time to attract birds to feeders if you are interested in the plumage and other color changes that occur seasonally.