Mike in the Wild

Apparently all birds molt to some degree, shedding and replacing their feathers in various stages over certain periods of time.  Feathers are critically useful but nevertheless dead appendages that wear out and become damaged, so regular replacements benefit the animal. Having observed hundreds if not thousands of birds in the last few years, I've only noticed the molting process a couple of times.  Most notably, I've seen a great-tailed grackle without his namesake tail.  During the short period without this appendage he still seemed to be able to fly. Early in January I photographed a male Costa's hummingbird at my Phoenix home's sugar water feeder.  Studying the pictures, I noticed the bird's bright amethyst colored gorget feathers were either damaged or missing.  Having seen some diseased hummingbirds at my feeder in past seasons, I feared maybe he was sick.   Not finding a lot of time to research a new avian disease, a few weeks later I phot...