Double- Crested Cormorant
When
it comes to fishing technology, few anglers can compete with the
advanced skills of the double-crested cormorant. The
double-crested cormorant (Phalacrocorax auritus) is a
goose-sized bird with a yellow throat patch highlighting a black
iridescent green or purple body. It has bright turquoise eyes,
webbed feet and a long black, hook-tipped, slender bill. In the
spring, adult cormorants have two small tufts of feathers on
either side of their head, a trait that gives the species its
name.
For a species that was nearly placed on the endangered species
list in the 1960's, the double crested cormorant, often called
the water turkey, has made an incredible recovery. This
fish-eating bird suffered a near demise earlier in the century
due to the use of DDT, which thinned the birds’ egg shells,
causing them to break under the weight of the incubating parent.
Since the banning of DDT, and through continued protection under
the Migratory Bird Treaty Act of 1918, populations have
increased to around two million birds, leading anglers and aqua
culturists to ask the U.S. Fish and Wildlife Service to devise a
plan for curbing cormorant numbers.
Cormorants are water-loving birds that choose nesting and
roosting habitats safe from ground predators but close to
feeding areas. When on the water, they are sometimes mistaken
for geese and loons because of their longs necks, head and bill.
Cormorants fly in the shape of a “V” just like geese, but often
glide while flying which is uncharacteristic of geese.
Cormorants are rarely vocal when flying.
Oklahoma’s numerous reservoirs and abundant fish populations are
an eye-opening treat to upwards of 50,000 cormorants migrating
to and from breeding grounds during spring and fall. The large
numbers of double crested cormorants may not be welcomed with
opened arms, but they stand as a testament of how successful
conservation efforts can be.
Cormorants almost always nest in colonies, which may comprise
more than a thousand breeding pairs. They build their nests of
sticks and coarse vegetation on cliff ledges, in trees in or
near water, or on the ground. Two nesting colonies have been
found in Oklahoma, but the primary breeding ground is in the
northern United States and Canada.
Female double-crested cormorants begin breeding at age three or
four and usually only have one brood per year. They lay three to
five chalky pale blue eggs in April that hatch after 25-28 days
of incubation. At seven weeks, the young are able to join the
adults to feed and at ten weeks the young are fully independent.
Double-crested cormorants are opportunistic fish-eating birds
preying on a variety of fish, but concentrating on those that
are easiest to catch. Their webbed feet, positioned far back on
their bodies, propel their streamlined frames to depths of 20
feet or more in search of prey. They can remain underwater for
about 30 seconds. On average, double-crested cormorants forage
60 minutes per day and consume one pound of food.
Although expert swimmers and divers, cormorants look like they
struggle to stay afloat. They are commonly seen with only their
heads and necks exposed from the water. Cormorants lack the oil
glands that other water birds have so their feathers don’t repel
water well. They perch on rocks or in trees with their wings
half open to dry in the sun. To take off from water, cormorants
gain speed by tiptoeing along the surface while flapping their
wings.
Upwards of 50,000 double crested cormorants winter in Oklahoma
every year. Hopefully, we will find a way to balance this
ecological success story with our state’s aquatic resources.