Sandhill Crane
The
sandhill crane (Grus canadensis) is one of the two crane species
native to North America. It is a large, wading bird with long
black legs, long neck, and black, chisel-shaped beak. Adults are
usually four feet tall, with a wingspan of about six feet.
There are six recognized subspecies of the sandhill crane, with
three being migratory and the remaining being non-migratory. The
lesser sandhill crane subspecies is migratory and can be found
during the winters in the southcentral United States and Mexico.
There are about 550,000 sandhill cranes in the mid-continental
population, which accounts for at least 80 percent of all
sandhill cranes. They migrate through a zone called the Central
Flyway, each spring to breed in the north-central U.S., Canada,
Alaska and Siberia.
Sandhill cranes mature at three to five years of age and mate
for life. Cranes prefer to nest in remote, inaccessible wetland
areas. They construct simple nests by scraping vegetation into a
mound. In late April or early May, they typically lay two
oval-shaped eggs. The eggs are greenish or brownish with dark
spots.
Both males and females take turns incubating the eggs for one
month. The chicks are tawny-colored and develop rapidly. Since
incubation begins as soon as the first egg is laid, the eggs
hatch a day or two apart. The older chick is more likely to
survive, and within 10 weeks the young, called colts, are ready
to take their first flight.
Adult plumage is attained by about two years of age. Mature
birds are gray with white cheeks and a bare reddish forehead.
Some of the mature birds’ plumage takes on a rusty color, which
is caused by the iron stain picked up in the peat bogs and
muskegs of their breeding ground.
Cranes are omnivorous ground feeders and will eat frogs,
rodents, insects, bulbs, seeds, and berries, as well as aquatic
invertebrates and animals. They also have adapted to agriculture
by feeding on waste grain and small animals in farm fields.
Sandhill cranes have a variety of vocalizations, but have loud,
unmistakable voices. Their trachea is long and forms a loop
within the breastbone, making their voices quite powerful. Their
calls can be described as a loud, rolling, musical rattle, or a
repeated series of trumpeting “garoo-a-a-a” calls that can be
heard at a distance of more than a mile.
What the cranes may be more famous for is their lively dancing
displays. Their display is usually associated with a courtship
ritual, but it can also be used in aggression, facilitating pair
formation, and sexual synchronization. The dance includes
bowing, skipping and jumping, and cranes will also pick up
sticks and repeatedly throw them up in the air. When it occurs
in a flock, the dance will start slowly with one bird, then as
other birds join in, the tempo speeds up. It is certainly a
remarkable sight.
The sandhill crane is sometimes confused with the great blue
heron (Ardea herodias). Though they have similar appearances,
there are a few key differences. Sandhill cranes fly with
outstretched necks, while herons fly with their head and neck
tucked back into an “S” shape. Sandhill cranes have a rapid
upstroke when flying, and herons have a slow, steady flap.
Cranes nest separately on the ground, while herons nest in
rookeries, which are large colonies in the trees. Cranes also
have a loud, trumpet-like call, whereas herons emit hoarse
croaks.
Coyotes, bobcats, and eagles are some of the sandhill crane’s
predators, but human influence also puts them at danger.
Destruction of marshland for development and some agricultural
practices continue to be a threat, especially in the Central
Platte River Valley of Nebraska. Their shrinking available
roosting space is threatening their populations, as well
populations of other animals, including endangered whooping
cranes and least terns.
Sandhill crane fossils dating back six million years have been
found in Nebraska, making it the oldest bird species still
living today. They were hunted by native peoples, early pioneers
and through regulated management can still be hunted today in
Oklahoma.