Double Crested Cormorant is a voracious fish eater.
These strange looking water birds can weigh up to five
and a half pounds. They have a long, sharp, hooked beak
and are strong swimmers with webbed feet and powerful
legs. They are very quick and mobile underwater, and are
capable of diving to at least twenty five feet.
has been estimated that cormorants can consume up to
half of their body weight in fish and crustaceans each
day. That body-weight to fish-consumption ratio is even
higher among immature birds. The preponderance of that
diet is composed of small fish.
Cormorants are extraordinarily efficient fishers. They
consume most small fish that they catch while diving
underwater. They only bring the larger fish to the
surface where they toss the fish in the air and then
swallow it head first.
largest colony of nesting Double Crested Cormorants in
the Western United States and Canada is located at the
mouth of the Columbia River. This colony numbers about
13,000 breeding pairs plus immature birds.
their migration out to sea, young salmon smolts become
disoriented when they encounter saltwater for the first
time in the River estuary. These temporarily stupefied
fish are easy prey for the cormorants. The U.S. Army
Corp of Engineers estimates that cormorants kill and
consume about twenty million salmon smolts each year in
the Columbia River estuary.
These federally protected migratory birds are found
nesting all along the Pacific Coast and on inland
waterways as well. Another very large nesting colony is
found at the mouth of the Klamath River where they prey
on out-migrating Klamath River Chinook and Coho salmon
smolts in that estuary. Government agencies have no
estimate of how many smolts are killed by cormorants in
the Klamath River.
Under the protection of the international migratory bird
treaties, cormorants have been increasing in population
about three percent per year, for the last several
decades. They are so tightly protected that biologists
have generally been unable to even take enough birds to
confirm estimates of their rates of depredation.
Cormorants do spit up the undigested bones that they
have consumed in small pill-like balls. Biologists are
able to get a rough idea of what the cormorants are
eating by analyzing these regurgitated bones.
Cormorants readily and efficiently feed on fresh water
fish. Oregon Coastal lakes have been known for their
exceptional bass fisheries for decades. Many believe
that the influx of cormorants has virtually eliminated
natural reproduction among bass in these fresh water
lakes because they are only able to find either newly
hatched or large bass in those coastal lakes. The
cormorants appear to fish so efficiently that they kill
and eat almost all of the young bass in these lakes
before the fish can mature.
why am I talking about coastal cormorants, salmon and
What is NOT commonly known is that
the second largest nesting colony of Double Crested
Cormorants in the Western United States and Canada is
located on Upper Klamath Lake. There may be as many as
six thousand breeding pairs of these birds reproducing
in the Upper Klamath Basin.
Cormorants prefer to nest in trees. Unfortunately, their
fecal accumulations on and under the trees often cause
the trees to die. This is likely what has caused the
death of many trees adjacent to water bodies including
the stately old pine trees where the cormorants nest
along the banks of the Lost River near Olene.
These Upper Klamath Basin cormorants also feed primarily
on fresh water fish. We can be certain that the birds
are not feeding on salmon smolts in Upper Klamath Lake.
So what are the Cormorants eating?
Lost River and Short Nosed Suckers are listed as
endangered in the Upper Klamath Basin. They continue to
be listed primarily because the young fish are
disappearing from the reproduction cycle even though the
early recruitment of suckers appears to be phenomenally
successful. It appears that tens of millions of sucker
eggs successfully hatch each year.
biologists tell us that the yearling sucker fish simply
disappear from the system. They are only able to find
very young suckers or mature sucker fish. This is eerily
similar to what has happened to the young bass in
Oregonís coastal lakes.
we overlooking the obvious? Except for at the mouth of
the Columbia River, Upper Klamath Lake has more
Cormorants than any other place in the entire Western
United States and Canada.
would seem that cormorants would be super-efficient
fishers in a lake as shallow as Upper Klamath Lake. Is
sucker predation, by the ever increasing number of
federally protected cormorants, responsible for the
unexplained loss of yearling suckers?
Biological science is too often based on false premises.
Federal, State and Tribal biologists have assumed that
the reduction in the numbers of endangered suckers is
the result of man-caused changes in their habitat.
Hundreds of millions of taxpayer dollars have been spent
on studies and restoration activities designed to
improve that sucker habitat.
Biological Opinion that requires the maintenance of
artificially high Upper Klamath Lake levels is based
upon improving sucker habitat. This Opinion has
persisted in spite of the fact that the National Academy
of Sciences determined that these elevated lake levels
would not help the suckers and might even harm them.
Enforcement of that Biological Opinion deprives the
Klamath Project irrigators of much of the water that is
stored for the irrigation of their land.
Most of the Tribal science used in determining the Upper
Klamath Lake Total Maximum Daily Load was gathered for
and was predicated upon restoring sucker habitat. That
science generally assumed that man-caused ecological
changes have resulted in water quality degradation that
is causing the demise of the suckers.
after all these studies and related management
modifications, virtually no positive change has occurred
as measured by either adult sucker fish recovery or
water quality improvement. What has changes is that
irrigated agriculture in the Upper Klamath River Basin
is being irreparably harmed.
Isnít it time for the biologists to start questioning
their own assumptions? Isnít it time for them to expand
their hypotheses to include other potential causes for
reduction in sucker numbers?
am neither a bird nor a fish biologist. However, during
nearly thirty years of veterinary practice, I always
remembered and attempted to apply the advice of one old
veterinary college professor. Doctor Koger began every
lecture by telling our class that we should never
overlook the obvious.
When will the biologists look to see if the immense
population of Double Crested Cormorants living in the
Upper Klamath Basin may be simply eating the young
Please remember, if we do not stand up for rural Oregon
no one will.