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Let's Learn About Cranes !
When
you are done
click here to play
a game to
test your knowledge of cranes.
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Cranes are large, beautiful, graceful, long-lived
birds which have inspired awe among people for millennia. For many cultures, particularly
in the Orient, cranes have a deep cultural and mythological significance. For conservation
projects the beautiful and charismatic cranes provide the incentive to conserve wetlands
and grasslands upon which many other less charismatic, but equally important species, also
depend. The crane family is also widespread, existing on five of the seven continents.
(Only Antarctica and South America do not have cranes.)
Preserving cranes and their habitat requires
a careful, disciplined, and holistic approach to their conservation. Of the 15 species of
cranes, eleven are vulnerable to extinction, making cranes one of the most threatened
families of birds in the world. The two species of cranes that call North America home,
the Sandhill and Whooping Cranes, demonstrate the range of population sizes. The adaptable
Sandhills are the most numerous of all cranes with an
approximate population of over 500,000 birds.
Whooping Cranes, however, are the rarest of all cranes with a total population of
approximately 500 birds.
Other similar-looking
birds include herons, storks, and spoonbills, but they are not closely
related to cranes. Rather, these different families of wading birds have
evolved similar adaptations to living in wetlands. In North America, coots
and rails are the crane's closest relatives.
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![Black-crowned Crane](../Images/bl-crowned.jpg)
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The Black
Crowned Crane |
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Individual and Social Behavior
Cranes pursue small prey, and
sometimes each other, by running. A running crane takes one to three steps per second and
may use its wings for balance and to gain speed. While a running crane looks awkward, they
can easily outrun humans. Cranes do not have webbed feet, but they can swim, although
adult birds usually avoid deeper water unless necessary. Chicks are good swimmers and may
leave the nest to follow the parents through the wetlands, sometimes within a few hours of
hatching.
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![Sarus Crane](../Images/sarus.jpg)
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Sarus
Cranes |
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Feathers give cranes both the ability to fly and to regulate their temperature. Made of
the same material as human fingernails, feathers require constant attention. A crane
preens by nibbling the base of a feather and then drawing it through the bill. Preening
straightens and closes repairable gaps in the feather. When preening, cranes may apply oil
to the feathers obtained from a special gland located on top of the tail. Contrary to
previous belief, the oil does not serve as waterproofing, but helps condition the feathers
and may also have fungicidal and antibacterial properties. Prolonged preening sessions
follow water or dust bathing. While cranes spend a great deal of time caring for their feathers, the feathers
still wear out and are replaced during a seasonal molt. Many crane species are flightless
during the molt, which usually occurs during late spring when the adults are raising their
chicks. It is not unusual for flightless cranes to stay near heavier cover until they and
their young can fly. Cranes, such as the crowned cranes, living in predator-dense areas
lose their feathers over a longer period of time and never become flightless.
Sandhill Cranes and Eurasian Cranes
"paint" themselves by preening mud into their feathers prior to the breeding
season. Painting acts as camouflage, helping the cranes hide amid the brown vegetation of
an early spring marsh. Siberian Cranes also paint themselves, but only at the base of the
neck. This "makeup" indicates that the birds are in their prime and ready to
breed.
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![Grey Crowned Crane](../Images/gr-crowned.jpg)
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The Grey Crowned Crane |
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Cranes are aggressive birds. When fighting, they leap into the air to rake opponents with
their sharp claws or stab at an opponent with their bill. This continues until one bird
runs or flies away, sometimes closely pursued by the victorious bird. Fighting is
dangerous to both participants, however, so cranes use a complex system of threat
behaviors allowing rivals to avoid fighting. Communication includes both physical postures
and vocalizations. Ruffle, drop-wing, and crouch threats indicate low-, mid-, and
high-intensity aggression levels respectively, so many aggressive encounters are resolved
before fighting becomes necessary. (The animated picture on the top shows a crane
performing a ruffle threat; the picture on the bottom show a crane performing a crouch
threat.) Most crane species also will flash the bright red patch on top of their heads to
an opponent or predator to indicate growing excitement. |
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Vocalizations
The contact call is made by both
chicks and adults. Adult contact calls consist of a soft, purring call while a chick's
contact call is high-pitched. This call alerts nearby cranes to the caller's whereabouts.
The chick distress calls sound similar to their contact calls, but are louder and more
strident--parents react quickly to them. At about three months of age, chicks are able to
perform the guard call, a single loud call that warns other cranes of danger.
The most significant vocalization
is the "unison call." The unison call consists of a complex, but carefully
orchestrated duet performed by a mated pair of cranes. The call helps to form or reinforce
pair bonds and also acts as a territorial warning to other nearby cranes. In many species,
the female has a two-note call while the male has a single-note call. Males of some
species, such as the White-naped, Siberian, and Brolga, may flex their wings while unison
calling. Members of a pair usually stand within a few feet of each other while unison
calling. A unique call made by the Grey Crowned Cranes is "booming." Small
"gular sacs," which hang below the chin of the birds, inflate increasing call
resonance. Crowned cranes also use a "quack" call to locate their mates.
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![Black-necked Crane](../Images/bl-necke.jpg)
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The Black
Necked Crane
(If a menu pops up on downloading
~ download to CURRENT LOCATION.) |
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Flight and
Migration
Cranes typically run into the wind
to achieve the lift necessary for flight, but if alarmed a crane can spring directly into
flight. Cranes may fly as fast as 52 m.p.h. during level, flapping flight, but prefer to
soar, especially during migration. When soaring in thermals (updrafts of warm air), cranes
will circle until they reach a desired altitude, usually between 3,000 and 5,000 feet.
Once the appropriate altitude is reached, the cranes leave the thermal and glide forward,
slowly losing altitude. They then find another thermal and repeat the procedure. While
slower than level flapping flight, soaring conserves energy.
Cranes prefer to migrate at
altitudes of less than 5,000 feet, but some species are forced to fly much higher. In
North America, mountain ranges run north and south and birds migrate parallel to them. In
Asia and Europe, however, mountain ranges, such as the Himalayas and Pyrenees, generally
run east and west forcing cranes and other birds to negotiate mountain passes as high as
20,000 feet.
Daily flights may range from a few
miles in bad weather to several hundred miles if suitable stopover points are unavailable.
Cranes often migrate in large flocks when conditions are favorable. At night, migrating
cranes often roost at "staging areas" in water that is 4-8" deep. Staging
areas usually consist of safe roosting sites in shallow marshes or on submerged river
sandbars. There are usually good foraging areas within a short flight of the roosting
sites and cranes may remain at staging areas for several weeks as they regain energy and
rest. Staging areas of some species are traditional resting spots that have been used for
hundreds and possibly thousands of years. Examples of staging areas used by Sandhills
include the Platte River (Nebraska), Jasper-Pulaski State Wildlife Area (Indiana), and the
Sandhill Wildlife Demonstration Area (Wisconsin). |
![Eurasian Crane](../Images/eurasian.jpg)
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The Eurasian Crane
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Feeding
Feeding is one of a cranes' most
time-consuming activities. Cranes spend most of the daylight hours in areas where food is
most abundant. Cranes forage for roots and the starchy swellings found on the roots of
certain plants called tubers. They also eat seeds, small mammals and reptiles, eggs of
other birds, and invertebrates, such as worms, clams, insects, and crayfish.
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![Whooping Crane standing over nest.](../Images/whooping.jpg) |
The Whooping Crane
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Nesting and
Reproduction
Cranes are territorial during the
breeding season, with each pair defending an area in which it will attempt to raise young.
Sandhills may nest in areas of less than three acres, but the average territory size is
larger than 50 acres. Larger crane species typically have larger territories. Territories
will tend to be smaller in areas where there is abundant food, good nesting sites, and
high crane population densities.
Most crane species nest in shallow
marshes, but Demoiselle and Blue Cranes build scant nests in dry prairie or savanna,
although usually within a few hundred yards of a water source. In deeper marshes, cranes
build massive nests from nearby wetland plants. Often a "moat" forms around the
nest because the cranes use so many of the nearby plants for constructing the nest. Nests
may be five to six feet across and tall enough that the water does not reach the eggs.
Nest construction takes from one to seven days.
Once the female lays the eggs, the
pair shares incubation duties "exchanging" the incubating responsibilities about
every two hours during the day, although towards the end of the incubation the nest is
exchanged more often. This gives both birds a chance to feed and exercise. At night, it is
thought the female does the bulk of the incubation, while the male stands guard nearby.
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![Sandhill Crane](../Images/sandhill.jpg)
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The Sandhill Crane
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The time of hatching
coincides with the emergence of insects on which the young will feed. Timing of the hatch
is particularly important for migratory cranes so the young can grow and gain the size and
strength necessary to migrate before winter sets in. Timing is less important with
non-migratory cranes which live closer to the tropics. Both parents feed the chicks, but the male
usually feeds the chicks first. The newly-hatched chick may be offered small pieces of the
egg shell or the female may consume the shell, perhaps to replenish the calcium used from
her body to coat the eggs. Often the shell is simply carried away from the nest and
discarded as not to attract predators. Both parents brood the young birds to protect them
from both cold and precipitation. Brooding also helps warm the chick during the first few
days after hatching when it cannot control its own body temperature. The family leaves the
nest after the second chick hatches, but may return to the nest for several evenings to
brood the chicks during the cool of the night. |
![Brolga Crane and Chicks](../Images/brolga.jpg) |
A Brolga Crane and Chicks |
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Population
Dynamics
Cranes have low reproductive
capabilities making it difficult for them to replace losses due to hunting, natural and
human-caused disasters, predation, accidents, and disease. Cranes do not begin nesting
until they are 3-7 years old and then they generally lay just two eggs each year. Of the
two eggs, usually only one chick will survive. Cranes, however, may live for 25-30 years
in the wild and the one chick they raise each year will likely fledge and join the
migratory flock. The survival strategy of cranes, therefore, is the opposite of animals
like rabbits or mice, which have short lives and high reproductive rates. Recruitment
rates (the number of young in the flock each fall) varies from species to species, but
ranges from about 10-14% for Sandhill Cranes.
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![Demoiselle Crane](../Images/demi.jpg) |
Demoiselle
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Legal Protections
Cranes have both formal and
informal protections around the world. Informal protections may include religious or
cultural protections. Formal protections include state or local laws against the direct
taking of individuals, and may, or may not, include protections for habitat. Laws against
direct taking are often poorly enforced. In North America, hunting of cranes is regulated
by state, provincial and international treaty.
The Migratory Bird Acts of 1916
(between the U.S. and Canada) and of 1936 (between the U.S. and Mexico) regulates hunting
of migratory species. It is illegal under these acts to take or possess regulated species
or their parts (including eggs and feathers) unless there is a legal hunting season on
that species, or if the person possessing the bird has been granted a permit for
scientific purposes or for captive propagation. The U.S. also has the Endangered Species
Act which protects rare species and its habitat, especially areas designated as critical
habitat.
-
The
International Crane Foundation
When
your done click
here to play a game
to test your
knowledge of cranes.
(Population
information was updated February, 2008)
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![Wattled Crane](../Images/wattled.jpg) |
The Wattled Crane
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Used with
permission from the International Crane Foundation
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![](../Images/Back_Track_3.gif)
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