SPRING 1999/VOLUME 13, NUMBER 2
Mysterious Bill Deformities
Biologists search for answers
The United States Geological Service (USGS) Biological Science Center of Alaska is investigating dozens of reports of beak deformities in Black-capped Chickadees. As many as 85 reports-many provided by Feeder- Watchers-have been documented in south-central Alaska during the past two winters. Scientists are testing these birds for disease, parasites, abnormal bone structures, genetic abnormalities, contaminants, and are also attempting to determine whether any connection exists between the beak deformities and an ongoing spruce beetle epidemic in south-central Alaskan forests, the largest such epidemic ever recorded in North America. As many as half-a-dozen chickadees with beak deformities have also been documented in recent years in other parts of the continent.
FeederWatchers Report Chickadee Deformities
In late November, Bob and Anne Winckler were FeederWatching from the dining room of their Wasilla, Alaska, home, just north of Anchorage, when a Black-capped Chickadee showed up on the ground under their feeders. The bird appeared to be carrying something small, dark, and sharp, with a slightly downward curve.
"Then we looked again and thought it might have something stuck in its beak." But Bob says that after moving closer to the bird, he and Anne finally concluded the chickadee wasn't carrying anything in its bill. "The beak itself was the length and shape of a small bent twig."
They saw that both the bird's upper and lower mandibles were longer than usual. The upper mandible in particular was grossly long and decurved, crossing to the right over the straighter, shorter lower mandible. The bird's odd beak inspired the Wincklers to nickname it "Cyrano" after the flamboyant cavalier with the nose in the play, Cyrano de Bergeerac. The Winklers began a daily watch of Cyrano's eating and social behaviors.
Because the bird couldn't easily eat black-oil sunflower seeds like the other chickadees, it came up with its own feeding strategy-one that involves the local Downy Woodpeckers.
When the downies visit the Winckler's double suet feeder and start pecking away at the fat, Cyrano quickly flies underneath. He's figured out that woodpeckers are messy suet eaters, and if he flies under the feeders, he can claim the fallen crumbs. The suet-a peanut butter suet with some nutmeats-is easier for the bird to eat than the shell-covered sunflower seeds.
But it takes special maneuvering for the chickadee to eat anything. Grasping a piece of food with its elongated beak, Cyrano flies to a flat surface, such as a patch of packed snow. Somehow it has to get the food all the way from its longish beak into its mouth opening. Tucking its head far down between its legs, close to its feet, it can feed in a number of ways.
The Wincklers have seen the bird turn its head sideways and brush the ground to push the food toward its mouth. They've observed it lifting a foot to its beak to move the food back, and they've watched it grab food out of its beak or from the ground with one foot and deliver the morsel directly to its mouth opening. Sometimes the bird teeters. To keep from rolling over, it extends its left wing and leans slightly.
Despite the feeding hardship, Cyrano fed successfully during a week-long February cold spell when temperatures dropped to 40 degrees below zero (Fahrenheit). During that time, the Wincklers often saw Cyrano perched near a heating vent on their rooftop; they suspect the bird also found shelter under their back porch.
Several months after Cyrano arrived, two other long-beaked chickadees showed up at the Winckler's feeders. Their beaks were not as grotesque as Cyrano's. But both of these birds disappeared during the February cold. None of the odd-beaked birds was well tolerated by the other chickadees. The three often got into food squabbles with the other birds and always allowed the normal chickadees to dominate. Mostly, they stayed to themselves.
James Elson on Alaska's Kenai Peninsula is another FeederWatcher who's had a strange-beaked Black-capped Chickadee at his feeders. When his chickadee first showed up last November, Elson thought it had a twig stuck in its nostril. But upon looking closer, he saw that its beak was longer than normal and that it was both decurved and crossed.
He noticed that the bird with the deformed beak would feed only after the normal chickadees had flown away. When temperatures dropped below zero in December, the other birds disappeared. The deformed-beaked chickadee stayed on, finally getting the feeders all to himself. But after two weeks of feasting, it vanished.
What's Causing the Chickadee Beak Deformities?
André Dhondt, director of Bird Population Studies at the Lab, says the cause of the chickadee beak deformities in Alaska is probably impossible to pinpoint right now, because there are a number of possible causes of such malformations. He explains that bird beaks are like human fingernails-soft structures that actually grow at a constant rate all the time. One regulator of beak growth, however, is the hardness of the food a bird eats. In general, the harder the food, the more wear on the beak. Regular bill use keeps bill growth in check.
In addition to a bird's diet, injury, diseases, and parasites can affect beak growth.
USGS biologist Colleen Handel says she'll continue to count on FeederWatchers and other people who monitor backyard birds to help document any chickadee or other species' beak deformities as the USGS investigation continues.
For more information or to report your own sightings, telephone (907) 786-3418, or visit the web site at http://www.absc.usgs.gov/research/bpif/bpif.html.