More than 200 reports of Black-capped Chickadees with bill deformities have been reported since the first sighting in 1991. Most are from Anchorage with others ranging from Fairbanks to Kenai. A few sightings have come from King Salmon and Dillingham. Bill deformities have also been reported in other birds such as woodpeckers, grosbeaks, nuthatches, jays, and magpies. Odd, and quite disturbing, is that most occurrences are in Alaska. Only a few have come from the lower 48 or Canada: one in Wisconsin, Connecticut, Vermont and two in Ontario, Canada.

Colleen Handel, a Wildlife Biologist with the U.S. Geological Survey, is studying the occurrences of Black-capped Chickadees with bill deformities and is trying to determine a cause for this. These bill deformities have mainly been long, curved bills instead of the usual short, pointed bills. Bird bills are always growing, sort of like fingernails. In normal birds their bills will wear down with pecking.

Some of the birds examined had abnormalities in the bone underlying the bill sheath that may have caused the bill to become offset and grow abnormally. Possibilities for this include disease, parasites, trauma to the tip of the bill, nutritional deficiencies, genetic abnormalities, or exposure to contaminants. Tests for evidence of parasites or disease have been negative. Tests for contaminants have not been conclusive. PCBs and some pesticides are known to cause bill deformities. Potential pesticides could be ones used on spruce bark beetles.

Two occurrences of Black-capped Chickadees with bill deformities have been seen in the Dillingham area. The first was observed on Wood River Road during the winter of 1997/1998. The second was observed in the area of the Lake Road and Waskey Road junction in July 1999.

Articles regarding this phenomenon have appeared in the Anchorage Daily News, Alaska Magazine, public service announcements, and on the U.S. Geological Survey web page at www.absc.usgs.gov. If you observe birds with any unusual deformities please contact the Togiak National Wildlife Refuge at 842-1063. For Field Notes, I’m Rob MacDonald.