Tuesday, November 09, 2010

Alaskan Birds with Beak Deformities

An unusually high number of birds with beak deformities have turned up around Alaska, according to the USGS. According to a statement issued by the agency, the birds most affected have been Black-capped Chickadees and Northwestern Crows.

In birds affected by what scientists have termed “avian keratin disorder,” the keratin layer of the beak becomes overgrown, resulting in noticeably elongated and often crossed beaks, sometimes accompanied by abnormal skin, legs, feet, claws and feathers. Biologists with the U.S. Geological Survey’s Alaska Science Center published their findings in this month’s issue of The Auk, a Quarterly Journal of Ornithology.

“The prevalence of these strange deformities is more than ten times what is normally expected in a wild bird population,” said research biologist Colleen Handel with the USGS, “We have seen effects not only on the birds’ survival rates, but also on their ability to reproduce and raise young. We are particularly concerned because we have not yet been able to determine the cause, despite testing for the most likely culprits.”

The disorder, which has increased dramatically over the past decade, affects 6.5 percent of adult Black-capped Chickadees in Alaska annually. Beak deformities in this species were first observed in the late 1990s and biologists have since documented more than 2,100 affected individuals. Increasing numbers of other species have also been observed with beak deformities throughout Alaska, British Columbia, and Washington. An estimated 17 percent of adult Northwestern Crows are affected by avian keratin disorder in coastal Alaska.

A variety of other Alaskan species have also been found with beak deformities, though not to the same extent as Black-capped Chickadees (pictured above) and Northwestern Crows (pictured right). An online gallery shows images of those two species, plus American Kestrel, Common Raven, White Pelican, Downy Woodpecker, Red-breasted Nuthatch, European Starling, Northern Flicker, Steller's Jay, Rough-legged Hawk, Red-shouldered Hawk, Red-tailed Hawk, Red-winged Blackbird, Yellow-rumped Warbler, Black-billed Magpie, Black-crowned Night Heron, Orange-crowned Warbler, and Clark's Nutcracker.

According to the USGS, beak deformities can have a variety of causes, so more research is needed. Possible candidates include pollution, poor nutrition, and diseases. Deformities have sometimes been traced to specific pollutants such as agricultural runoff.

To learn more, you can explore the USGS beak deformity website, which includes a section on how to help (if you live in Alaska or the Pacific Northwest) and links to articles the research team has published about the beak deformity problem. The two recent Auk papers are both downloadable at the last link.