|
Description:
|
Two species of sandhill crane occur
in California. The greater sandhill crane, which
can get as tall as five feet with a wingspan of seven feet, is listed
as a California State Threatened species. Of the 15 crane species in
the world, 12 are listed as either threatened or endangered. The
greater sandhill crane lives an average of 15 to 20 years in the wild,
but some individuals have been reported to be 40 years old at the time
of death. The lesser sandhill crane, which can get as tall as four
feet, has a more stable population in California. Throughout most of California these birds are only winter
residents, arriving in large flocks around September and October and
leaving around March and April. The greater and lesser sandhill cranes
have very similar winter plumages. The body and neck are almost
entirely gray, although some individuals may have rust specks on the
wings. The head is the most distinguishing feature, with white feathers
on the lower half and a bright red crown.
These magnificent birds spend their summers in and near wet meadows and
freshwater wetlands north of California. In winter they can be found in
grasslands, freshwater wetlands, and croplands. They tend to frequent
corn and rice croplands that have been recently harvested and offer
plenty of foraging opportunities. Sandhill cranes are rarely found in
areas with trees. Instead they prefer the open habitat that allows them
to see their prey easily. These cranes are omnivorous, meaning they eat
both plant material and animals. Their diet includes a wide variety of
foods, including cereal crops, grasses, seeds, grains, roots, worms,
insects, mice, snakes, frogs, and even small birds and bird eggs!
Sandhill cranes are active during the day and spend their evenings
roosting in large flocks. When migrating, these large birds will fly
day and night, stopping very seldom.
The greater sandhill cranes nest in northeastern California and southern Oregon. The courtship period begins in
April and the peak of the breeding season occurs from May to July.
Courtship begins with an intricate dance that can include up to 80
individuals. During the dance the birds make loud calls and run towards
each other with their wings extended. The peak of the breeding season
is from May through July, and nesting is usually completed by late
August. During this time both the male and female take part in nest
building. The nests, which are often piles of sticks and grass, are
built on the ground. They are only built in areas with surrounding
water or undisturbed habitat. Most nests are found on small islands
where the birds will be well-protected from predators. The female lays
between one and three eggs, with two being the average clutch size.
Both the male and female incubate the eggs for approximately one month,
at which time the eggs hatch. The young are raised by both sexes.
Although the young can usually fly at about two months old, they may
remain with the parents for up to one year. Sandhill cranes typically
raise one brood per year. The young can begin breeding at four years of
age.
The breeding habits of sandhill cranes are very interesting. Both sexes
take part in the entire process, from nest building until the young
become completely independent. Sandhill crane pairs are monogamous, and
many remain paired for life. The pair may even return to the same
breeding ground each year, and some pairs even use the same nest
multiple years in a row. During the breeding season, these birds may
protect a territory as small as 3 acres and as large as 400 acres! The
average breeding territory is between 40 and 60 acres.
The greater sandhill cranes, and the other 11 threatened or endangered
crane species, have experienced population declines largely as a result
of wetland habitat destruction. In some cases, these birds require
large breeding territories. During the breeding season they are
extremely sensitive to human disturbance, even as far away as one mile.
Sandhill cranes are also very sensitive to grazing.
|
|
References:
|
Ehrlich, P.R., D.S. Dobkin, D.
Wheye. 1988. The Birder’s Handbook: A Field Guide to the
Natural History of North American Birds. Simon & Schuster, Inc.
Miklos D., F. Udvardy. 1994. National Audubon Society Field Guide to
North American Birds, Revised Edition. Alfred A. Knopf, New York.
Peterson, R.T. 1990. Peterson Field Guide to Western Birds, Third
Edition. Houghton Mifflin Company. Boston and New York.
Sibley, D.L. 2000. The Sibley Guide to Birds. Alfred A. Knopf, New York.
Zeiner, D.C., W.F. Laudenslayer, Jr., K.E. Mayer, M. White (editors).
1990. California’s Wildlife, Volume II,
Birds. State of California, The Resources Agency, Department
of Fish and Game, Sacramento, California.
|
