It's one of the most pathetic sights to greet a backyard birder. Cardinals are normally robust and commanding in their brilliant crimson plumage. But every summer I get reports of "bald" cardinals. The descriptions range from birds with merely "unkempt or scruffy looking heads" to "miniature vultures." Over the years, I've seen a few myself. And of course, everyone asks what's wrong with these birds.
I've always attributed the condition to a bad case of ectoparasites -- mites and/or feather lice that actually eat feathers. Since the head is the one part of the body a bird can't reach with its bill to preen, it seems logical that a severe case of lice or mites could be responsible.
A cause: But recently I've read several reports blaming the condition on an unusual molt pattern. Normally song birds molt, or replace their body feathers, just a few at a time, so it's hard for even a keen observer to notice. For all the head feathers to fall out at once would certainly be unusual and hardly beneficial. The skin could get sunburned by day or badly chilled at night or during rain storms. One of the purposes of feathers, after all, is to protect the body from the elements.
Instead of relying on speculation or anecdotal reports for an explanation of bald cardinals, I decided to check with some experts. My first call went to Dr. Gary Ritchison, an ornithologist at Eastern Kentucky University and author of Wild Bird Guides: Northern Cardinal (1997, Stackpole). He told me he has, "... handled thousands of cardinals while mist-netting and banding over the years and only a few have had naked heads. None of those had severe mite or lice problems." He attributes the phenomenon to an odd simultaneous molt.
My next call was to Dr. David Bird, an ornithologist at McGill University in Quebec and author of The Bird Almanac (1999, Firefly Books). Like me, Bird always assumed this was a parasite problem, but a colleague, Dr. Rodger Titman (and no I'm not making these names up) argues strongly for the unusual molt explanation. "At this point, Rodger has convinced me that an irregular molt is the better answer.".
Another suggestion: Dr. Sylvia Halkin, an ornithologist at Central Connecticut University and co-author of the cardinal account in The Birds of North America (1999, No. 440), suggested in print that unusual feather loss may be due to a delayed response to injury. She also directed me to Dr. Chris Thompson. "Chris knows more about cardinal molt than anyone in the country. If anyone has an answer, he will," she said.
Thompson is an ornithologist with the Washington Department of Fish and Wildlife and has been studying molt for years. When cardinals just lose their crest or their heads appear scruffy, he explained, that's probably the result of molt. "Most birds become secretive and less active while molting, so we don't see them very often in this condition, " he said. "Since we don't often see actively molting birds, we perceive the condition as rare although it's probably just rarely seen.".
When I asked about cardinals with completely naked heads, Thompson paused, then said, "That's not normal. When birds molt, new feathers push out the old ones, so a head should never appear completely naked. Parasites might be the answer.".
Scratch your head: Next time you see a bald cardinal (or other backyard bird), blame molt if the bird looks like it's having a bad hair day. But if the head is completely naked, just scratch your head. Turns out, it's another fascinating backyard natural history mystery that we can't yet explain. Sometimes I like being reminded we don't know it all.
Correction: In last week's column on the Arctic National Wildlife Refuge, I gave an incorrect web address for the Amory Lovins' Rocky Mountain Institute. It is www.rmi.org (not ".com"). My apologies.