April 14, 2004

Deformed beaks pose riddle

Environmental pollution suspected of harming Alaska's birds.

by Michael Hopkin
Nature News

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A growing incidence of beak deformities among Alaska's birds is ruffling environmentalists' feathers. Puzzled experts suspect that pollution may be behind the phenomenon, though they admit that the cause is still unknown.

Outsized curved beaks up to three times their usual size have been spotted in some 30 species of bird so far. In many cases, the beak is so long that the bird is unable to feed or preen effectively, and ultimately dies.

Isolated cases of beak deformation have been seen in other places before, but not in such startling numbers, experts say.

The latest sightings bring the total number of Alaskan cases to around 1,800 since the first deformities were spotted in black-capped chickadees near Anchorage during the 1990s. Crows in southeastern Alaska are the latest to fall victim, says Colleen Handel of the US Geological Survey's Alaska Science Center in Anchorage, who has been tracking the outbreak.

"When I talk to birdwatchers, it's clear there has been an increase over the years," says Handel. The fact that deformed beaks are now cropping up in the southeast shows that the problem is spreading geographically, she says.

But no one yet knows what is responsible for the birds' blighted beaks. Handel and her colleagues have few leads to work on - the large number of different birds affected rules out a species-specific cause, and the team has so far found no evidence of a disease.

Growing out of control

The deformities may be due to organochloride pollutants in the region, Handel suggests. Compounds such as polychlorinated biphenyls (PCBs) and dioxins - persistent pollutants pumped out by waste incinerators - could damage the birds' DNA, she points out.

Such damage could cause beaks to grow out of control, says Kirsty Peck, a wildlife adviser with the UK Royal Society for the Protection of Birds. "A bird's beak is like a human fingernail - there's a part at the base where it grows," she explains. If this growth point malfunctions, the beak could grow uncontrollably fast or be skewed sideways.

This effect could leave many Alaskan birds with beaks that do not wear away naturally as they feed, Peck says. But she adds that this offers no hint of what is causing the damage to the DNA in the first place.

Other experts, however, are confident that pollution is to blame. "This sounds like a pretty classic case for organochlorides," says Diane Henshel of Indiana University in Bloomington, who has studied similarly afflicted birds in North America's Great Lakes region. "Jaw deformities are seen quite clearly with PCBs and dioxins."

Henshel suspects that the chemicals affect beak development in growing birds, rather than causing genetic defects at birth. Newborn chicks usually look fine, she explains - curved bills tend to show up after several weeks.

None of the Alaskan species is in imminent danger of extinction. But Henshel says that the case represents another example of the threat that industry poses to wildlife.

"I see it as an argument for combating pollution," she says. In the long run, she argues, removing pollution will be cheaper than treating or artificially feeding individual birds.

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