The Mystery of Deformed Beaks

Readers of Birding magazine saw a grotesque photographic gallery three years ago—a set of portraits of birds in Alaska and Washington with terribly deformed beaks. The shocking images accompanied an article by Caroline Van Hemert in the September/October 2007 issue.

Van Hemert described large numbers of Northwestern Crows and Black-capped Chickadees in Alaska and Washington whose beaks were excessively elongated, crossed, bent at right angles, and aberrant in various other ways that left us amazed that these birds could even grasp food and perform their essential preening. She told us in her September/October 2007 article that she and her team were hoping to find the cause. (Below: Black-capped Chickadee. Anchorage, Alaska, 10 January 2007. by © John DeLapp)

We received a saddening update this week in a paper in The Auk. By now, deformed beaks have been reported in more than 2,500 individuals of 29 species and a hybrid in Alaska alone. The paper’s authors, Colleen Handel, Lisa Pajot, Steven Matsuoka, Caroline Van Hemert, John Terenzi, Sandra Talbot, Daniel Mulcahy, Carol Meteyer, and Kimberly Trust, term the phenomenon is “the largest epizootic of gross abnormalities ever recorded among wild bird populations.”

Research so far has characterized the syndrome as primarily affecting the keratin layer of the beak, possibly representing abnormally rapid growth of the rhamphotheca—the horny outer layer that covers the beak. Yet, despite intensive efforts, the underlying pathology and possible mechanisms of the disorder remain unknown.

Here are the birds with beak deformities reported in Alaska: Pacific Loon, Bald Eagle, American Kestrel, Peregrine Falcon, Sandhill Crane, Black-legged Kittiwake, apparent Glaucous-winged x Herring Gull, Downy Woodpecker, Hairy Woodpecker, Steller’s Jay, Black-billed Magpie, Northwestern Crow, Common Raven, Black-capped Chickadee, Chestnut-backed Chickadee, Boreal Chickadee, Red-breasted Nuthatch, Ruby-crowned Kinglet, American Robin, Varied Thrush, European Starling, Orange-crowned Warbler, Yellow-rumped Warbler, American Tree Sparrow, Savannah Sparrow, Lincoln’s Sparrow, Dark-eyed Junco, Pine Grosbeak, Common Redpoll, and Pine Siskin. (Below: Northwestern Crow. Juneau, Alaska, 20 August 2006. by © Ben Mitchell)

Think about that taxonomic diversity. It spans not only different species, genera, and families, but even different avian orders: Gaviiformes, Falconiformes, Gruiformes, Charadriiformes, Piciformes, and Passeriformes. This disorder, then, extends a long way through the avian class. How far it may spread, either geographically or to additional species, is a worrisome question.

The researchers have encountered dead end after dead end in their attempts to pinpoint the cause. Studying four abnormal Black-capped Chickadees, they saw no evidence of lesions in the bill skeleton or the cranium. They found no bacteria or viruses, and no sign of reduced bone density. Three of the chickadees had unidentified feather lice, and two had unidentified feather mites but with no signs of infection. Chickadees studied for other possibilities produced no evidence that the condition was congenital or that damage from chemical pollution was involved.

In many of the species, only one or a few individuals had the abnormality, leading the authors to suggest that the causes may have been unrelated. At the other extreme, the average annual prevalence of beak abnormalities was estimated at 6.5 percent of adult Black-capped Chickadees in south-central Alaska from 1999 to 2008 and a shocking average of 17 percent of adult Northwestern Crows captured at six sites in Alaska during 2007 and 2008.

Clearly, a lot more research is needed, and birders can help. The U.S. Geological Survey’s Alaska Science Center wants reports from observers who see a bird with a deformed beak. Extensive details about the malady and the research are available online: http://tinyurl.com/ysmzsj. The website includes a form for reporting sightings. Such reports are essential for tracking the potential spread of this insidious abnormality.