For the Birds Radio Program: Alaska Chickadees with Deformed Bills
Since 1991, the Alaska Biological Science Center has been amassing records of birds with deformed bills. At first there weren’t many, but over the past two years there has been a dramatic increase. Most of the birds with the deformity have extremely elongated, curved and crossed beaks. As of December, 2000, a minimum of 533 Black-capped Chickadees have been observed with the deformity, making chickadees by far the most vulnerable to whatever is causing this. 98 individuals of 19 other species have also been found to have deformed bills, including magpies, crows, Steller’s Jay, Downy Woodpecker, Peregrine Falcon, and Golden-crowned Kinglet.
The vast majority of the reports have been from the past two winters. The Boreal Partners in Flight has a website with a chickadee alert, including a graph that shows the dramatic increase since the first cases were detected in 1991. Compared with the 533 records of deformed chickadees in south central Alaska, since 1986 there have only been 8 Black-capped Chickadees with bill deformities reported in all the rest of North America. These are all of single birds from different locations and different years, dating back to 1986, including three from Ontario and single birds from Vermont, Connecticut, Washington, Minnesota, and Wisconsin. Most of the Alaska cases have been reported in the south-central part of the state, but ominously, during the past two summers,. researchers working in other parts of Alaska captured a Yellow-rumped Warbler with a crossed bill in Denali National Park and Preserve, a deformed Ruby-crowned Kinglet in Tok, a deformed Savannah Sparrow in Yakutat, and a deformed Peregrine Falcon chick on the Colville River on the North Slope.
Some of the chickadees with deformed bills are managing rather well, though the deformed bills are usually so bad that it’s impossible for the chickadees to crack open seeds, so they are quite dependent on suet and peanut butter at feeders. Because the bills stick out unusually far, some of the birds can only pick up pieces of food dropped by other birds, and they can only get it by turning their faces to pick up the morsels sideways.
What is causing the problems? At this point no one knows for certain. Bill deformities are known to be caused by many different factors, including blunt trauma to the bill, disease, parasites, nutritional deficiencies, genetic defects, exposure to extreme heat, and exposure to various contaminants. An examination of deformed birds in 1999 showed no evidence of disease, parasites, or fractures of the bone underlying the sheath of the bill.
Researchers did find evidence of higher levels of genetic damage in the abnormal birds compared with normal birds, which can be caused by exposure to contaminants. When researchers tested tissues of the chickadees directly for some common contaminants, they found very low concentrations of PCBs and DDE. These are both organochlorine compounds, which are known to cause deformities in other species, but the concentrations were too low in the chickadees to suggest that they were the cause. So scientists are checking a wide variety of other possibilities, but the research is necessarily painstakingly slow.
There aren’t many birds on this planet that bring people as much pleasure and joy as chickadees, so seeing photos of chickadees with such an awful deformity was sobering. . No matter what species is in trouble, it seems to me that we humans should do something about it, but when the species is a chickadee, somehow it seems more urgent. Attention must be paid.