Class: Aves (Birds)
Body height: tallest—sarus crane Grus antigone, 5.7 feet (1.76 meters); smallest—demoiselle crane Anthropoides virgo, 3 feet (0.8 meters)
Weight: heaviest—red-crowned crane Grus japonensis, 17 to 22 pounds (7.7 to 9.9 kilograms); lightest—demoiselle crane, 4 to 7 pounds (1.8 to 3.1 kilograms)
Life span: 20 to 40 years
Incubation: 28 to 36 days
Number of eggs laid: 1 to 4 eggs per clutch
Age of maturity: 2 years
Conservation status: Siberian crane Grus leucogeranus is at critical risk; whooping crane Grus americana and red-crowned crane are endangered.
• Not only is the sarus crane the tallest of the crane species, it is also the tallest flying bird!
• Queen Marie Antoinette of France gave the dainty demoiselle crane its name. Demoiselle means maiden, or young lady, in French. The queen was enchanted by the crane's delicate and maidenly appearance.
• Ancient Greeks believed the flight of cranes inspired the god Hermes to invent the Greek alphabet.
• Fossil records show that crowned cranes existed 37 to 54 million years ago! Prehistoric cave paintings of cranes have been found in Europe, Africa, and Australia.
• Sandhill crane Grus canadensis chicks have been known to start swimming when they are only six hours old.
• The founder of the International Crane Foundation, Dr. George Archibald, is the 2005 Zoological Society of San Diego Conservation Medalist.
Elegance and grace: by any other name, a crane
From their powerful calls to their intricate dances, cranes have enchanted people for centuries. These birds fly through Australian and Native American legends and European folklore, and some species are considered sacred in Asia. Cranes are large birds with long necks and legs, streamlined bodies, and long, rounded wings. Their size and graceful proportions make them easy to recognize by all. Cranes are some of the tallest birds in the world. In flight, their bodies form a straight line from their bills to their toes, presenting a beautiful, elegant image.
Dance! Dance! Dance!
All cranes, young and old alike, participate in elaborate, enthusiastic "dancing," often just for the fun of it! For the young, dancing helps to develop physical and social skills. It serves as a courtship ritual for the single adults and gets established pairs ready to breed, too. In a flock of cranes, once a dance starts, it can quickly become contagious, with all the cranes joining in. Although dance patterns differ among crane species, all patterns have long, detailed sequences of coordinated bows, leaps, runs, and short flights. During a dance, the cranes will pick up sticks, grass, feathers, or whatever small objects are near, tossing them up into the air with their bills. The dance of the demoiselle crane Anthropoides virgo has even been described as an avian ballet.
No picky eaters here
Cranes are omnivores that eat everything from snails to acorns to insects to snakes. They readily change their eating habits to take advantage of whatever is available. Anatomy plays a part in what a crane species prefers to feed on. Shorter-billed cranes, such as the black crowned crane Balearica pavonina, will eat insects as well as graze on grasses. Long-billed cranes, such as the brolga Grus rubicunda, will probe in shallow wetlands for crustaceans and other aquatic life. The bigger crane species have large, powerful bills and dig up roots and tubers out of the muddy wetlands. Cranes at the San Diego Zoo and the San Diego Zoo Safari Park are offered a specialized commercial crane feed, greens, and mealworm larvae.
The children, the children
Cranes can lay up to four eggs in a clutch, but two eggs are more common. Eggs laid in warmer climates are white or light-colored to help the eggs reflect excess heat. Eggs laid in colder regions are darker in color so the eggs will absorb heat. While some species will only raise one chick, others will raise two. Since one chick will always become dominant, the weaker chick will often die if food is scarce.
Crane chicks are precocial, and parents begin feeding them almost immediately after they hatch. Chicks are mostly a light brown, with a few species being silver gray. These colors provide camouflage against predators. The chicks grow very, very quickly and soon learn to follow their parents to food sources. Sometimes, adults will feed chicks until they are several months old. The youngsters develop their flight feathers at two to four months of age, preparing them for long migrations. During their second year, adult feathers gradually replace the juvenile plumage.
Read my body and hear me roar
Cranes are highly social birds, usually pairing for life and living in flocks that can be quite large. Of course, living closely together can give rise to disagreements, so cranes need good communication skills. Like flamingos, they deal with their issues using body language common to all crane species. There is recorded evidence of at least 90 different types of these elaborate visual displays. Here's what some of them mean:
Aggressive— The crane stands tall with body feathers smooth, head features expanded. Then it walks stiffly, followed by wing flapping, ruffles, bows, false preening, stomps, nasal snorts, and growls.
Submissive— The crane lowers its head and head feathers and walks in a loose and wary way.
Crouch Threat— The crane bends its legs, lowers to the ground, folds its wings loosely against its body and the ground, and places its head forward with the red patch prominent.
Ruffle Threat— The crane raises the feathers of its neck, wings, and back, partially opens and lowers its wings, ruffles them alternately, then lowers its bill in a preening movement, finishing with a low growl.
Charge— The crane points its neck and head straight down and lifts the feathers along its neck and back, holding the stance for several seconds.
These remarkable birds also have a vast vocal communication system. Each species has its own tone and volume, from the soft honks of the crowned cranes to the flutelike call of the Siberian cranes Grus leucogeranus. Crane chicks start to learn their “language” as soon as they hatch and will know at least six calls by the end of their first year. By this time their voices have also deepened, becoming louder and stronger. The call of a whooping crane Grus americana can often be heard from a mile away.
Boy, are my wings tired!
Some crane species are migratory: Siberian cranes, sandhill cranes Grus canadensis, Eurasian cranes Grus grus, whooping cranes, and demoiselle cranes. Some of their migrations are of epic proportions in terms of distance and altitude. Once the average altitude of about 6,500 feet (2,000 meters) is gained, they assume a V-formation and glide, calling to each other constantly. Whooping cranes have been known to fly as far as 500 miles (800 kilometers) in a day, although about 186 miles (300 kilometers) is the average.
The highest-flying award goes to the Eurasian cranes, flying over the Himalaya Mountains at altitudes up to 32,800 feet (10,000 meters). That’s cruising altitude for jetliners! Meanwhile, some of the small demoiselle cranes navigate through the passes of the Himalayas in their migration, while others fly across the vast deserts of the Middle East and northern Africa. The lesser sandhill crane Grus canadensis canadensis wins the distance award for the longest migration, flying from eastern Siberia across the Bering Sea into North America, sometimes as far south as northern Mexico.
The whooping crane: back from the brink
Whooping cranes are the tallest birds in North America. They were once numerous in the prairie wetlands of the United States and Canada, but European settlers drained the wetlands to build farms and cities and hunted the large birds for their meat. By 1941, only 15 birds were observed at their wintering area on the Gulf Coast of Texas. To help save the birds from extinction, refuges were established, the birds were carefully monitored, and hunters were educated about the harm they could do to the species. Through intensive efforts, a traditional flock has slowly been built up to around 200 birds. This flock is the only natural, self-sustaining whooping crane flock left in the world. There is also a small, nonmigratory flock of approximately 85 whooping cranes established in Florida. Whooping cranes are still endangered but there is certainly more hope for the species these days.
More help for cranes
All crane species are rapidly dwindling. Cranes need large areas of habitat, which is gradually being turned into farm and housing use. Even the marshes where cranes nest are being slowly drained for agricultural purposes. In 1973, the International Crane Foundation was founded to be the world center for the study and preservation of cranes. It has become a world leader in crane conservation, including the breeding of endangered species. San Diego Zoo Global works with the Foundation, providing cranes for breeding and helping with wetland conservation work in China. It is hoped that the haunting calls of wild cranes will continue for many generations to come.