Threatened western yellow-billed cuckoo nestlings in their nest

Threatened western yellow-billed cuckoo (Coccyzus americanus) nestlings in their nest in southern Arizona. The nestlings' feather sheaths (as seen on these young) break and are groomed off by the young bird all within a couple of hours' time, so that the bird transforms from the scaly-looking creature here to a fluffy little fledgling within a single day. Photo by Charles Drost, SBSC, USGS.