Molting or mites? Seeking an explanation for 'bald birds'

Lillian DeDomenic of Monroeville was snapping photos of birds in her backyard when one in particular caught her eye.

At first, she wasn’t sure what it was. It had red body plumage, but its head was a deep gray, and as she looked closer, it didn’t appear to have any feathers on its head at all.

Then she realized: It was the male cardinal who’d been showing up lately, only now he appeared to be bald for some reason.

“This guy had been a frequent visitor for a couple of weeks,” DeDomenic said. “He’s been coming with a female. Then all of a sudden he shows up like that.”

Annie Lindsay, program manager for the bird-banding program at Powdermill Nature Reserve in Cook , said it might look strange or unusual, but all birds go through it.

“Right now is molting season, so all birds are going through a molt that will continue into the fall,” she said. “Some birds will lose a lot of the feathers on their head. They’ll look a little derpy for a while.”

Molting serves two purposes: it replaces worn or damaged feathers, and it allows birds to grow different types of plumage indicating its age, sex or the season of the year. Many birds have different summer and winter plumage.

“All birds are going to lose all the feathers on their body at some point,” Lindsay said. “And it’s usually sequential.”

According to the Avian Report website, most birds begin molting with their primary flight feathers, starting near the body and working outward toward the wingtips. This, along with tail molting, is the most easily visible sign.

Well, that and apparently the head.

“This is the first year I’ve had them at the feeders, so I was pretty intrigued,” DeDomenic said.

National Aviary Ornithologist Bob Mulvihill, however, is not so sure that traditional molting would produce fully “bald” birds.

“The other theory is that the birds have an infestation of ecto-parasites, typically feather mites or feather lice, that kind of end up gathering around the head, because that’s the only place the bird can’t reach when it’s preening,” Mulvihill said. “My intuition is that sometimes, those mites or lice have done enough chewing to damage the feather, it will cause the birds to scratch their heads more than normal, and those feathers can break off.”

And while it appears to be limited mainly to cardinals and blue jays, “it does bear some further investigation,” Mulvihill said.

The appearance of “bald” birds is not at all related to the mysterious illness that has been affecting songbirds throughout the mid-Atlantic this spring and summer.

The main visible symptoms for that are swollen eyes or crusty discharge around the eyes, as well as off-balance movements. Scientists at the U.S. Geological Survey, the Smithsonian and universities are still working to determine its causes.