CRANES: Gruidae

PHYSICAL CHARACTERISTICS

Cranes are tall birds with large wings, long legs, and long, graceful necks. Most species are black and white or gray in color. Often there are bright patches of bare red skin that are shown in threat and dance displays.

GEOGRAPHIC RANGE

Cranes are found on all continents except for Antarctica and South America.

HABITAT

Most cranes live in wetland habitats. Breeding generally occurs during the summer in freshwater wetlands. Some cranes spend the winter in coastal saltwater marshes. A small number of crane species live primarily in grassland habitats.

DIET

Grassland crane species primarily eat insects and seeds and have relatively short bills. Cranes with medium length bills eat insects and seeds from grain fields, in addition to a wide variety of plant and animal matter from wetland areas. Cranes with long bills use one of two feeding strategies. "Diggers" dig holes in wet mud to look for tubers, root vegetables like potatoes. The holes are sometimes 1.6 feet (0.5 meters) deep. "Catchers" look for live animals on the ground.

BEHAVIOR AND REPRODUCTION

Many cranes are migratory, meaning they travel from breeding (summer) areas to wintering areas each year. Some species travel thousands of miles during their migration. In many species, breeding occurs during the wet season. During the non-breeding dry season, cranes may gather in large flocks, or groups of birds. This flocking behavior is believed to allow individuals to find mates.

Cranes have loud, trumpeting calls. These calls are used to communicate a wide variety of messages to individuals of the same species. A contact call is given between individuals that know each other, such as a crane and its mate or a parent and its chicks. Other calls used by cranes signal aggression, an intention to fly, pain, or a warning of danger. The unison call is made simultaneously by a male and female pair and is intended to warn other cranes away from their territory.

In addition to calls, cranes also have elaborate displays, characteristic motions used in communicating with others of the same species. These displays can involve raising feathers around the head, unique motions of the bills, and exposing and/or changing the size of red skin patches on the heads that are normally covered by gray feathers. Displays are often used to threaten other cranes or to express submission to a more dominant crane. Conflicts that are not resolved by a threat display proceed to a ritualized fight that will not seriously injure either crane. The ritualized fight involves leaping up with the legs folded, and then using the legs to push at the other bird's breast. Conflicts between cranes are particularly common during flocking, when large numbers of birds are gathered together.

WETLAND LOSS AND CRANE ENDANGERMENT

Because of the loss of wetland habitats in many parts of the world, cranes that are more heavily dependent on wetland areas tend to be the most endangered. These include the Siberian crane and the whooping crane. Crane species that use grassland habitats more frequently, especially those that have learned to hunt for food in agricultural fields, have tended to thrive. These include the demoiselle, sandhill, and Eurasian cranes.

Cranes are monogamous (muh-NAH-guh-mus), a single male breeds with a single female. Cranes often mate for life. They are also territorial; a pair of cranes will defend their area of land, or territory, against other cranes of the same species. Nests are built within the wetland or grassland habitat. Females generally lay two eggs at a time and both parents incubate, sit on and warm the eggs for chick development. Eggs hatch after about a month, and offspring are able to fly after about two or three months. However, young cranes usually remain with the parents until about nine months of age. If both eggs hatch, one of the crane offspring is generally dominant to the other, that is, it has higher rank and receives more food from the parents. In the majority of cases, only the dominant offspring survives from each nest.

CRANES AND PEOPLE

Cranes symbolize good luck in many places throughout the world. The whooping crane is used as a symbol of conservation in the North American because it nearly became extinct before intense efforts by the United States and Canada helped populations increase in number.

CONSERVATION STATUS

Of the fifteen crane species, one is listed as Critically Endangered, facing an extremely high risk of extinction, or dying out, in the wild. Two are listed as Endangered, facing a very high risk of extinction in the wild, and six are listed as Vulnerable, facing a high risk of extinction in the wild, by the World Conservation Union (IUCN).

GRAY CROWNED CRANE (Balearica regulorum): SPECIES ACCOUNTS

Physical characteristics: Gray crowned cranes are named for their characteristic crown of gold feathers. They have a pale gray neck and red throat wattles. The rest of their bodies are black, white, and gold in color. Gray crowned cranes are 39 to 43.3 inches tall (100 to 110 centimeters) and weigh anywhere from 6.6 to 8.8 pounds (3 to 4 kilograms). They have a wingspan of between 71 and 79 inches (180 to 200 centimeters).

Geographic range: Gray crowned cranes are found in portions of eastern Africa.

Habitat: Gray crowned cranes occupy both wetland and grassland habitats.

Diet: Gray crowned cranes eat a wide variety of food items, but focus primarily on seeds and insects.

Behavior and reproduction: Gray crowned cranes are frequently found in trees. Individuals nest in wetland or grassland areas. Instead of building their own nests, gray crowned cranes frequently use ground nests that have been abandoned by other large bird species. In general two eggs are laid. Both the male and female incubate, or sit on, the eggs. These hatch after about a month and the young are able to fly after two or three months. However, they may remain with their parents for as long as nine months.

Gray crowned cranes and people: The gray crowned crane is the national bird of Uganda. It is also regarded as an important symbol in other parts of its range, including Kenya, Namibia, South Africa, and Zambia.

Conservation status: Although gray crowned cranes are not currently considered threatened, many populations have declined due to the drainage of its wetland habitats. ∎

SANDHILL CRANE (Grus canadensis): SPECIES ACCOUNTS

Physical characteristics: Sandhill cranes have gray bodies, necks, and heads, and a bare patch of red skin on the top of the head. Individuals can achieve heights up to 47.2 inches (120 centimeters) and generally weigh between 7.3 and 12 pounds (3.3 to 5.4 kilograms). Sandhill cranes have a wingspan of between 63 and 82.6 inches (160 to 210 centimeters).

Geographic range: Sandhill cranes are found across North America from Quebec to British Columbia, and north to Alaska and eastern Siberia. Some populations also occur in portions of the United States and Cuba.

Habitat: Sandhill cranes inhabit wetland areas. In the winter it is sometimes found in grassland areas or agricultural fields as well.

Diet: Sandhill cranes have a varied diet including grains, berries, insects, and rodents.

Behavior and reproduction: Some sandhill cranes are migratory while others remain in their breeding areas all year round. During the breeding season, female sandhill cranes generally lay two eggs. Both parents incubate and feed chicks after they hatch. Chicks hatch after twenty-nine to thirty-two days and are able to fly by fifty to ninety days after hatching.

Sandhill cranes and people: Sandhill cranes are an important part of Native American culture. Elements of the cranes' mating dance appear in some Native American dances.

Conservation status: Of the six subspecies, population groups within a species, of sandhill crane, four are not considered threatened, but two subspecies, the Mississippi and the Cuban, are listed as endangered by the U.S. Fish and Wildlife Service. ∎

RED-CROWNED CRANE (Grus japonensis): SPECIES ACCOUNTS

Physical characteristics: Red-crowned cranes, or Japanese cranes, have white bodies and bare red skin on the top of the head. This crane is about 59 inches (150 centimeters) in height, 15.4 to 22 pounds (7 to 10 kilograms) in weight, and has a wingspan of between 86.6 and 98.4 inches (220 to 250 centimeters).

Geographic range: The red-crowned cranes are found in parts of China, Russia, Korea, and Japan.

Habitat: The red-crowned crane is a rather aquatic species among cranes. It inhabits both freshwater and saltwater wetlands and marshes as well as some rivers.

Diet: Red-crowned cranes eat a wide variety of items, including insects, fish, rodents, and plants.

Behavior and reproduction: Red-crowned cranes are well-known for their elaborate courtship dances. Generally, the female lays two eggs during the breeding season. Both parents incubate and feed the chicks after they hatch. Eggs hatch after twenty-nine to thirty-four days. The young are able to fly after approximately ninety-five days.

Red-crowned cranes and people: Red-crowned cranes are considered sacred in many parts of its range in East Asia. They are associated with happy marriages, love, long life, and good luck. Red-crowned cranes have frequently appeared in East Asian poetry and art.

Conservation status: Red-crowned cranes are listed as Endangered by the IUCN. ∎

FOR MORE INFORMATION

Books:

del Hoyo, J., A. Elliott, and J. Sargatal, eds. Handbook of the Birds of the World. Vol. 3, Hoatzin to Auks. Barcelona: Lynx Edicions, 1996.

Matthiessen, Peter. The Birds of Heaven: Travels with Cranes. New York: North Point Press, 2001.

Perrins, Christopher, ed. Firefly Encyclopedia of Birds. Buffalo, NY: Firefly Books, 2003.

Web sites:

"Cranes." Bird Families of the World, Cornell University. http://www.es.cornell.edu/winkler/botw/gruidae.html (accessed on April 5, 2004).

"Family Gruidae (Cranes)." Animal Diversity Web. http://animaldiversity.ummz.umich.edu/site/accounts/classification/Gruidae.html#Gruidae (accessed on April 24, 2004).

"Gruidae (Cranes)." The Internet Bird Collection. http://www.hbw.com/ibc/phtml/familia.phtml?idFamilia=43 (accessed on April 24, 2004).

International Crane Foundation. http://www.savingcranes.org/ (accessed on July 12, 2004).