http://www.nature.com/nsu/040412/040412-1.html
Deformed beaks pose riddle
Environmental pollution suspected of harming Alaska's birds.
14 April 2004
MICHAEL HOPKIN
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.
--------------------------------------------
Birding-Aus is now on the Web at
www.birding-aus.org
--------------------------------------------
To unsubscribe from this mailing list, send the message 'unsubscribe
birding-aus' (no quotes, no Subject line)
to
|
