Seems like lot of birds in my area (western NC mountains at about 3,000 ft) are just finishing up their molt - cardinals, mockingbirds, bluebirds,... Unless they are bald and shabby looking for other reasons. I don't think my other common feeder birds - nuthatch, brown thrasher, house finch, goldfinch, sparrow, chickadee, starling, dove, ... ever did it (or they hid when doing so).