For the Birds Radio Program: Molting
Every year at the end of July or beginning of August, I start getting letters and calls about weird-looking, even ugly, birds missing their head feathers. Sometimes people realize the bird they’re looking at is bald. Other times they think they’re seeing a mutant cardinal or jay–one missing its crest and bearing black or dark gray feathers on an exceptionally tiny head.
Many songbirds molt their plumage at the end of the breeding season. Food is abundant in much of northeastern North America this time of year, so as birds are recovering from the arduous nesting season and putting on fat to prepare their bodies for the coming migration, they also grow a new set of feathers. During molts, birds usually look at least a bit unkempt—new feathers push out the old ones when they first come through, at which point they’re encased in a tube called a sheath. When several feathers emerge together in an area, it will break up the plumage pattern and texture. For some reason, Blue Jays and Northern Cardinals are more likely to drop all their head feathers at once than many of their relatives, or at least both species are so conspicuous that we’re more likely to notice bald jays and cardinals than other species. This doesn’t seem to put them at any risk. As long as they have plenty of nutritious food, new feathers will grow back, and by molting them all at once, they can concentrate their molt into a shorter time period. Feathers are essential for birds both for insulating them against excessive cold and heat and for protecting their bare skin against the sun’s burning rays, but as far as we know, molting birds don’t seem to get sunburned, though that question probably does warrant further study just to make sure.
Many birds in late summer are very tricky to identify. Some are making the transition from breeding to wintering plumage. Male Scarlet Tanagers can appear to be a patchwork quilt of yellow and red, and American Goldfinches between brilliant yellow and a more dull, creamy color. The young of some birds are in a unique juvenal plumage. European Starling fledglings are a soft brown color completely unlike the adults. In August and September, these birds molt into their first adult plumage in patches, too. Young warblers can be in a plumage different from that of their parents, and some adult males molt out of their easy-to-identify feathers into duller versions, too. Peterson has a few pages devoted to teasing out identifications of what he calls “confusing fall warblers.”
However they look, birds seem to feel pretty itchy and uncomfortable during the molting process. Songbirds have thousands of outer feathers, and during a molt, each one is pushed out by a rapidly growing new feather encased in a tubular sheath. Birds seem to feel very itchy during this process, and their constant scratching and biting at the growing feathers crumbles away the sheaths. Right now my licensed education Eastern Screech-Owl is molting. Each week I fill my vacuum bag with piles of feathers and grayish white crumbly dust—all that remains of the feather sheaths. The molting process seems to challenge both a bird’s comfort and its dignity, especially when the head feathers fall out. Archimedes is living proof of what a mercy it is that birds never consult mirrors. In a few weeks he’ll be sporting a perfect set of feathers once again, but meanwhile, he’ll continue to constantly scratch and bathe and I’ll try hard not to offend his dignity by laughing at how funny he looks.