Refuge Notebook
Peninsula Clarion Article
Dated
2 March 2001
Unsolved Mystery: Deformed-Bill Black-Capped Chickadees
by Ted Bailey
Most of us like to believe that in
“pristine” Alaska we are immune from the ecological problems of the
“Lower 48.” There is increasing evidence, however, we are not exempt
from such problems, as the following strange puzzle will illustrate.
In
the last several years, south-central Alaska has seen a dramatic increase of black-capped
chickadees with deformed bills. Recently such birds have been seen in the Strawberry
Road and Poppy Lane areas. Biologists from the Alaska Biological Science Center
in Anchorage have been collecting these reports and are trying to discover the
cause of the deformities. Kenai Refuge biological technicians Todd Eskelin and
Stephanie Rickabaugh are capturing, leg-banding, and collecting blood samples
from black-capped chickadees on and near the refuge.
The chickadee bill
deformities range from barely detectable to grotesque. Sometimes the top bill
curves in a long U-shaped arc back towards the head. Such birds are unable to
pick up food in a normal fashion and must twist their head sideways to pick up
food with the side of the bill. Normal birds carefully preen their feathers, but
deformed-bill birds often look ragged and unkempt because they can’t properly
groom themselves. Usually, deformed-billed birds are observed at bird-feeders.
Could bird-feeders or commercial bird food be responsible for the deformities?
But, if so, why are few other bird-feeder species similarly affected?
We
don’t know why black-capped chickadees are the most affected birds. Their
cousins - boreal chickadees - rarely have bill deformities, and other species
such as red-breasted nuthatches are seldom affected. Nevertheless, there are some
interesting patterns that may or may not be relevant. Black-capped chickadees
are year-round residents; they don’t migrate to spend winters in, say, California
or Central America. This suggests that the deformity cause is restricted to Alaska,
specifically, so far as we know, to south-central Alaska.
Why are only
black-capped and not boreal chickadees affected? Boreal chickadees prefer spruce
forests, while black-capped chickadees utilize more diverse habitats including
deciduous forest. Could the deformity cause somehow be associated with their different
habitats?
Black-capped chickadees store food, primarily seeds, in trees
under bark, in crevices between limbs, and in other “secret” places
for later retrieval. This storage includes food from birdfeeders, such as sunflower
seeds and suet. Chickadees typically remove the shell from sunflower seeds before
caching them. At peak activity, a chickadee will store hundreds to thousands of
food items per day. In Norway, a related species stores 50,000 to 80,000 spruce
seeds each autumn. Could this food-caching behavior somehow be related to the
deformed bills? With the recent spruce bark beetle outbreak in south-central Alaska
and the spraying of trees in certain areas for protection against the beetle,
one might suspect that chemical spraying could be a potential factor. But again,
there is no “smoking gun” in the form of solid evidence for a chemical
cause; it is just another hypothesis to be evaluated.
Peninsula Clarion
readers can help us address this major “unsolved mystery.” If you observe
a deformed-bill chickadee or any other species, please report it to the refuge
at 262-7021, and report it to Colleen Handel at “colleen_handel@usgs.gov”
of the Alaska Biological Science Center in Anchorage. A small number of chickadees
were banded near Soldotna last week. Normal chickadees have an aluminum band on
their foot. Potential deformed-bill chickadees have a color band. If you see a
leg-banded chickadee (of either type), please report it to us at 262-7021. This
will show how far local chickadees travel. A leg-band number would also be helpful,
but the numbers are small and difficult to read unless the bird is close by or
you have a pair of binoculars or a spotting scope. We will keep Clarion readers
informed as this story unfolds.
--------------------------------
Ted
Bailey is a supervisory wildlife biologist and has been responsible for the Kenai
National Wildlife Refuge's biological programs for over 20 years. He and his staff
monitor and conduct studies of ecological conditions and wildlife on the refuge.
Previous Refuge Notebook columns are on the web at http://kenai.fws.gov. Excellent
photos of chickadees with deformed bills can be seen at http://www.absc.usgs.gov (click on “Chickadee Alert”).
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