The Whooping Crane
Contributed by the International Crane Foundation
adult whooping crane (Grus americana) is pure white in color with
black wingtips, black legs and feet, black facial markings, and a bare
patch of red skin on its head. First-year chicks also have black
wingtips, but their body feathers
are tawny brown and white.
Reproduction: Whooping cranes mate for life and may live up to 25 years or more in the wild. On the summer nesting grounds, a pair establishes a territory and performs elaborate courtship dances and rituals. If mating is successful, the female lays two eggs. Both the female and male take turns incubating eggs for a period of 29 to 30 days. Although both eggs may hatch, usually only one chick survives the first few months to reach fledging age (click here to listen to the chick call).
Migration Route: Offspring learn the migration route by following their
parents south in the fall and north the following spring.
Biologists estimate that there were between 700 and 1,400 whooping cranes alive in 1865. Their numbers dropped rapidly, however, and by 1890 the whooping crane had disappeared from the heart of its breeding range in the north central United States. By 1938, only two small flocks remained: one non-migratory flock in southwest Louisiana, and one migratory flock that nested in Canada and wintered in Texas.
A number of factors contributed to the whooping crane's dramatic decline. Shy and secretive birds, the whoopers were easily disturbed as European settlers expanded westward. Settlers, draining marshes and plowing prairies for agriculture, destroyed much of the birdâs nesting habitat. As the number of whooping cranes declined, hunters, hobbyists, and museum collectors scrambled to acquire the rare specimens and their eggs. The toll from hunting was particularly high from 1870 to 1924, when over 250 whoopers were killed.
By the winter of 1941-42, the migratory flock had dwindled to only 13 adult birds and 2 juveniles. Meanwhile, the Louisiana population was reduced from 13 to 6 birds following a severe storm in 1940. One by one, the remaining Louisiana birds disappeared, until Mac, the sole survivor, was captured in 1950. Shortly after his transport and release in Texas, however, Mac was attacked by local whooping cranes defending their territory, and was later found dead.
Wood Buffalo National Park
Allen searched thousands of square miles of Canadian wilderness before the breeding grounds were accidentally discovered in 1954. Returning from a forest fire near the Hay River, a fire crew sighted three whooping cranes from a helicopter. One year later, the nesting area was confirmed when Allen and Robert Stewart actually located a whooper nest.
Wood Buffalo National Park, straddling the border between the Canadian province of Alberta and the Northwest Territories, was established in 1922, chiefly for the preservation of the wood bison. Remote from any human disturbance, the park offered whoopers a deep and pristine wilderness in which to nest.
Whooping cranes arrive at Wood Buffalo from late April through May. Breeding pairs are often the first to arrive, returning to the same nesting territory each year. The whoopers defend their nesting sites with threat displays and vocalizations like the ãunison call,ä a loud duet in which the female produces two notes for every one of the male.
Pairs nest in shallow ponds where they build large nest mounds from surrounding vegetation. Recurring droughts at Wood Buffalo pose many threats to the Whoopers. When drought occurs, nesting sites become more accessible to wolves, bears, and other predators, which may take eggs or kill newly-hatched chicks. The amount of food available also decreases.
Because each pair returns to the same nesting area year after year, pinpointing nesting sites allows biologists to identify each family. With such a small flock, the genetic history of each individual is an important consideration in management decisions.
Aerial surveys located only 28 whooper nests at Wood Buffalo in the spring of 1994, down from 45 nests discovered the previous year. A late thaw may have prevented some pairs from nesting, and researchers suspect that a shrinking food supply on the Texas wintering grounds probably also contributed to the decline. Unable to build up sufficient fat reserves during the winter, pairs may have arrived at Wood Buffalo weak and chosen not to nest. In subsequent years, nesting attempts returned to previous levels with 49 documented in both 1997 and 1998.
From 1977 to 1988, chicks in Canada were color-marked with brightly colored, plastic leg bands. As a result, biologists were able to determine sex ratios in the wild population and age of first breeding. Another research breakthrough occurred in the autumn of 1981 when radio-tracking of Wood Buffalo cranes was initiated. Small radios attached to plastic leg bands were placed on chicks just before fledging, so that families could be followed during migration. These studies have produced valuable information on the duration, timing, and routes of migration, and on use of habitat.
Southward migration from Wood Buffalo begins in mid-September. Whooper parents with new chicks are usually the last to head south for the winter. The short summer season allows just enough time for the chicks to fledge before the cold weather arrives. The 2,500-mile migration route through Alberta, Saskatchewan, Montana, the Dakotas, Nebraska, Kansas, Oklahoma, and Texas takes approximately four to six weeks to complete. Frequent stops are made to feed and rest in areas free from human activity.
Migration is a dangerous time for whooping cranes and other migratory birds. Up to 80% of the losses in the Wood Buffalo flock may occur during this period. Collisions with power lines are a leading cause of death, especially for inexperienced young birds.
Aransas National Wildlife Refuge
Ongoing research and controlled burns on upland areas are performed to provide optimal foraging areas. Small animals and acorns are foods which are left exposed after a burn.
Although Aransas NWR is protected and managed, habitat degradation is still a major threat to the cranes. By 1941, the Gulf Intracoastal Waterway was dredged through prime whooper habitat. Boat traffic on the canal has caused erosion of important tidal marsh, and contaminants have been detected in the water. Steps are being taken to reinforce damaged canal shoreline with cement mats.
During the first years following establishment of the refuge, the whooper population fluctuated near the brink of extinction. In subsequent years, numbers climbed slowly and new peak levels are being reached. Despite a windy storm in November 1998 which blew some migrating whoopers off course, officials at Aransas NWR counted 183 birds wintering in Texas in January 1999. This is a record number of whooping cranes.
Since whooping cranes lay two eggs, but usually only one chick survives, one egg can be removed from each nest without decreasing the productivity of the wild flock. Both eggs are tested to ensure that one viable egg is left in the nest. If biologists encounter a nest where neither egg is viable, they replace one with a good egg taken from another nest. After each nest has been left with one healthy egg, the remaining eggs are taken into captivity. Due to the successful production of eggs from the captive flock, eggs are no longer being collected from the wild.
Captive breeding began to pay dividends in 1975, when whoopers at the U.S. National Biological Serviceâs Patuxent Wildlife Research Center (near Laurel, Maryland) first produced eggs of their own. Artificial insemination helped increase fertility of eggs, while sandhill cranes were used as surrogate incubators to improve the hatching success of the whooper eggs.
In 1989, Patuxent transferred 22 whooping cranes to the International Crane Foundation (ICF) in Baraboo, Wisconsin. Splitting the captive population between two locations reduced the chance that a single catastrophic storm or disease outbreak could wipe out the whole flock. [UPDATE NOTE: See Whooping Crane Population Totals.]
The Rocky Mountain Experimental Flock
The goal of this cross-fostering experiment was to have the sandhills hatch and rear their larger cousins, then lead the young whoopers on migration to safe wintering grounds at Bosque del Apache National Wildlife Refuge in New Mexico. The 850-mile migration route along the Rio Grande in central New Mexico is shorter and easier than the 2,500 miles traveled by the Aransas/Wood Buffalo flock. In the beginning, this cross-fostering program looked promising, but eventually it proved unsuccessful. Even so, much valuable information was learned. The sandhill cranes hatched and raised the whooping crane chicks, and the whoopers did migrate with their new parents, but when the whoopers reached breeding age they did not pair with other whooping cranes. The whooper chicks probably imprinted on their sandhill crane foster parents. This "identity crisis" disrupted their ability to later pair and breed with other whooping cranes.
The Rocky Mountain population peaked at 33 birds in 1984-85. After the introduction of 289 eggs, further additions were stopped in 1989. In February, 1999, a total of four whoopers remained in the Rocky Mountains. Two adults survived from the experimental flock, and two more were added in 1997 as a result of an experimental migration using an ultralight aircraft which led the whoopers to the wintering grounds at Bosque del Apache National Wildlife Refuge [UPDATE NOTE: In 2001, two whooping cranes remained in the Rocky Mountain population. It's now zero.]
The Whooping Crane Recovery Plan also calls for approximately 20 chicks to be released into Florida each year, forming the nucleus of a non-migratory population of whooping cranes. Since 1993, over 135 whooping cranes reared in captivity have been released into south-central Florida's Kissimmee Prairie. Although high mortality from predation by bobcats was experienced in the initial years that cranes were released, modification of rearing techniques and relocation of release sites helped reduce this problem. Approximately 73 of the released birds survived as of early 1999.(UPDATE NOTE: For recent numbers, click here.)
Because the cranes were raised in captivity by adult whoopers or by humans dressed in a crane costume, researchers do not expect the pairing problems which the whooping cranes at Grays Lake experienced. In 1996, two of the oldest whoopers (both 4 years old at the time) established a breeding territory, from which they excluded the locally abundant sandhill cranes and in which they built several nests. Unfortunately, no eggs have been laid yet, but this could be linked to the birds' youth and inexperience.
The Florida whoopers do not migrate, since they have no role model to teach them a route. By avoiding migration, they also avoid hazards such as power lines, hunters, and a lack of suitable stopover areas.
Meanwhile, experiments are underway to determine the best way to teach captive-bred cranes how to migrate. Kent Clegg, a rancher in Idaho, reared groups of sandhill and whooping cranes and taught them to fly behind his ultralight aircraft. In October 1997, he led 8 sandhills and 4 whoopers on an 800-mile migration to Bosque del Apache National Wildlife Refuge in New Mexico. Two whoopers and 2 sandhills were lost to accidents, hunters, and predators, but the surviving ultralight birds are fully incorporated into the wild, associating with wild cranes, utilizing river roosts and refuge corn fields, and joining the 6 surviving sandhills from earlier ultralight projects. (UPDATE NOTE: 2 WHOOPING CRANES REMAINED IN THE ROCKY MOUNTAIN POPULATION IN FALL 2001.)
In Ontario, Canada, Bill Lishman (of motion picture "Fly Away Home" fame) and his team from Operation Migration migrated with a group of sandhill cranes to Virginia in the fall of 1997. There are no wild sandhill cranes in that area of Virginia, and the experiment will help determine whether captive-reared, ultralight-led cranes will reverse the migration on their own, without the presence of wild cranes to stimulate the migration in spring.
Enduring harsh weather conditions and an ultralight-bird collision during flight training, a total of 7 sandhills made the trip and wintered in Airlie, Virginia. Six of the sandhills returned to Ontario on their own the following spring. The experiment was repeated in the fall of 1998, and in the fall of 2000, another successful ultralight sandhill migration project paved the way to try the experiment with endangered whooping cranes in fall 2001 as a technique to reintroduce the whooping crane to former range in eastern North America. [UPDATE NOTE: Even though they are members of an endangered species, the new Eastern flock is designated as a Nonessential Experimental Population (NEP) — "experimental" because it will be isolated from other populations of the same species, and "nonessential" because they will not be esssential to the survival of the entire species. Under this designation, the reintroducd whooping cranes will not receive full Endangered Species Act protection, which will allow greater management flexibility and also resolve some possible conflicts between people and whooping crane conservation.]
When the Recovery Plan goals are reached, and all three flocks have been self-sustaining for a minimum of 10 years, the species will be down-listed to threatened status under the Endangered Species Act. Efforts to help the species will then continue, but at a diminished level.
If these plans are successful, then this magnificent bird will have been saved from the brink of extinction. The whooping crane will endure as a symbol of conservation and international cooperation, and as a reminder of the precarious balance between mankind and nature.
The IUCN has categorized whooping cranes as Endangered (proposed) while CITES has classified this species as Appendix I.
Return of the Whooping Crane. Robin W. Doughty, 1989, University of Texas Press, Austin, TX.
Reflections: The Story of Cranes. Gretchen H. Schoff, 1991, International Crane Foundation, Baraboo, WI.
Seasons of the Cranes. Peter and Connie Roop, 1989, Wallace and Co., New York, NY.
Crane Music: A Natural History of American Cranes. Paul A. Johnsgard, 1991, Smithsonian Institution Press, Washington D.C.
For more extensive information on all cranes, the reader can check our annotated
bibliography. The following two links will take you to the Northern Prairie
Science Center website to "The
Cranes: Status Survey and Conservation Action Plan" authored by Curt
Meine and George Archibald (IUCN, 1996). Click here to view the
chapter on Whooping
Cranes. This publication is also available in hardcopy from IUCN Publications
Services Unit, 219c Huntingdon Road, Cambridge CB3 ODL, United Kingdom. E-mail: firstname.lastname@example.org