The whooping crane (Grus americana) occurs only in North America, specifically within Canada and the United States, and is North America’s tallest bird. It is a flagship species for the wildlife conservation movement in North America, as it symbolizes the struggle for survival that characterizes endangered species worldwide, as was noted in the international recovery plan in 2007.
Historically, more than 10,000 whooping cranes once populated North America. Its north to south range included Canada and the United State to Mexico, and its east to west range included the Rocky Mountains to the East Coast, as documented in the 5-year review in 2011. Population declines were caused primarily by shooting and destruction of habitat in the prairies from agricultural development, as was noted in the international recovery plan in 2007. The international recovery plan also notes that all whooping cranes alive today have come from the all-time low of 15 whooping cranes that were wintering at Aransas National Wildlife Refuge in Austwell, Texas in 1941. This is currently the best place to find this species during the winter, as noted by Cornell University in 2019. Cornell University also notes that in the summer, this species can be found at Wood Buffalo National Park in Canada and that Nebraska’s Platte River often hosts this species during migration.
Strict legal protection, habitat preservation, captive breeding, international cooperation between Canada and the United States have helped to promote recovery of this species. These successes are also because of collaboration among state and federal governments, non-governmental and non-profit organizations like zoos and other conservation groups, as well as private citizens. Whooping cranes continue to face threats from alteration and destruction of habitat - including migratory habitat and winter habitat - from wetland drainage, increased development and conversion of suitable habitat to agriculture. The increase in the frequency and severity of drought due to, as well as the reduction in river flows degrade migration roost habitat. In 1998, the Texas Parks and Wildlife Department documented that reduced freshwater inflows that are due to diversions, as well as withdrawals for agriculture and human use also have a negative impact on the species. They also noted that declines in blue crab populations from reduced inflow were a part of the many threats facing whooping cranes.
The whooping crane breeds, migrates, winters and forages in a variety of habitats, including coastal marshes and estuaries, inland marshes, lakes, open ponds, shallow bays,and sand or tidal flats, upland swales, wet meadows and rivers, pastures and agricultural fields, as was noted in the 5-year review.
The 5-year review also notes that the loss of wetlands to cropland conversion, urbanization, roads and powerlines, as well as wind farms, has a significant negative impact to the migratory corridor used by whooping cranes. Furthermore, decreases in river flows have degraded riverine migration habitat for this species and development is also encroaching on salt marsh habitat that is used by whooping cranes in the winter.
The land near a shore.
A considerable inland body of standing water.
A natural body of running water.
Areas such as marshes or swamps that are covered often intermittently with shallow water or have soil saturated with moisture.
Summer foods include large nymphal or larval forms of insects, frogs, rodents, small birds, minnows and berries, as R. P. Allen documented in 1956, and was later confirmed by N. Novakowski in 1966 and D.G. Bergeson and others in 2001. Allen and many others researchers documented that the whooping crane winter diet consists mainly of blue crabs (Callinectes sapidus), clams (Tagelus constricta) and Carolina wolfberry (Lycium carolinianum). Carolina wolfberry (Lycium carolinianum) is an important food for whooping cranes in the fall.
Whooping cranes live and travel alone, in pairs, as families or in flocks of 50 or more birds during migration as A.J. Caven and others documented in 2020. Cornell University also note that sometimes whooping cranes will flock with sandhill cranes, spending their time on the ground and in shallow water. Some restoration activities have focused on clearing and maintaining roost sites free of trees and shrubs, restoring and rehabilitating wetland meadows and marshes adjacent to river channels, as noted in the international recovery plan of 2007. Cornell University also notes that whooping cranes cannot land on trees and thus, do not use them, and that the strong homing instinct of whooping cranes limits their dispersal to new habitat.
Weight of the whooping crane ranges between 13.2 and 17.2 pounds (6.0 to 7.8 kilograms). Captive males average 16 pounds (7.3 kilograms) and females average 14 pounds (6.4 kilograms).
Adult plumage is primarily snowy white. Exceptions to the white plumage include the:
- Primary feathers, the largest flight feathers on its wing, are black
- Alula, specialized feathers attached to the upper leading end of the wing, are black or grayish
- Crown, which is a vivid crimson color and has sparse black bristly feathers
- Malar region, the side of the head from the bill to the angle of the jaw, has sparse black bristly feathers
- Nape, which has a dark gray-black wedge-shaped patch
When the wings are folded back, the black primaries and black or grayish alula are not visible. The bill is dark olive-gray outside of the breeding season, and lighter olive-gray during the breeding season. The area at the base of the bill is pink or rosaceous in color.
Upon hatching, the iris of the eye is blue, as observed by researcher Jane Chandler, with the Patuxent Wildlife Research Center and noted in the international recovery plan of 2007. Chandler also noted that it gradually turns gray in chicks and becomes yellow by the end of the first year. The legs and feet are gray-black in color.
Juveniles display a reddish cinnamon plumage. White feathers begin to appear on the neck and back at 120 days of age, and this white plumage replaces the reddish cinnamon plumage throughout the winter months. By the following spring, the plumage is predominantly white, and the dark red crown, lores, meaning the area between eye and bill, and malar areas have manifested. Rusty juvenile plumage remains only on the head, the upper neck, secondary wing coverts, which are smaller feathers that cover the middle of wing, and scapulars, which are the wing feathers that arise from the shoulder, as documented by J.D. Stephenson in 1971. Yearlings achieve typically adult plumage late in their second summer.
The common name whooping crane probably originated from the loud, single-note vocalization given repeatedly by the birds when they are alarmed.
Whooping cranes are tall, white birds with long necks and long legs. They have stout, straight bills. Their body is slender and widens to a plump bustle by the tail. When in flight, the wings of a whooping crane are broad and the neck is fully extended. Their wingspan is more than 7 feet. This species is monomorphic; both sexes stand about 5 feet (1.5 meters) in height when standing erect.
Whooping Cranes are monogamous, meaning that they mate for life, as was documented by D.R. Blankinship in 1976 and confirmed by others in the 1980s. However, Blankinship and others also observed that if a mate dies, this species will form another pair bond, sometimes within only a few days following the death of a mate.
Whooping cranes form their pair bonds at 2 or 3 years of age. Pair formation can occur rapidly, or it can be a lengthy process that develops over one to three winters, as documented by M.A. Bishop in 1984. Bishop and others also observed that new pairs often establish a winter territory near the winter territory of their parents. The courting rituals of whooping cranes include elaborate and energetic dancing displays during which the birds bob their heads, flap their wings, leap into the air and fling feathers and grass.
Whooping cranes may start nesting as early as 3 years of age, as documented by E. Kuyt and J. P. Goossen in 1987, but the average age of first egg production is 5 years. Eggs are normally laid in late April to mid-May. Whooping cranes may re-nest if their first clutch is destroyed or lost before mid-incubation, as documented by R.C. Erickson and others in the early 1980s, but E. Kuyt noted that re-nesting has only been documented a few times. A large majority of clutches contain two eggs, but clutches of one egg and three eggs have also been documented by Kuyt in 1995. Eggs in clutches of two are laid 48 to 60 hours apart and incubation begins with the first egg laid, which results in asynchronous hatching of the eggs. This asynchrony may follow the insurance hypothesis, meaning that the parents produce a back-up offspring in case the first one does not make it, as documented by S. Forbes and D. Mock in 2000. Asynchronous hatching may be an adaptation to the availability of food resources or habitat suitability. Those eggs that are laid after incubation has begun usually only produce fledged young if the earlier laid egg fails to hatch or the chick dies soon after hatching. Therefore, although whooping cranes may lay two eggs, only about 10% of families arriving on the winter range have two chicks, noted R.C. Erickson in 1975. However, in years with suitable habitat conditions, crane pairs have been known to raise two young, noted B.W. Johns in 1998.
Eggs are light brown or olive-buff, with the blunt end of the egg bearing a concentration of dark, purplish-brown blotches. Egg length averages approximately 4 inches (100 millimeters), while width averages 2.5 inches (63 millimeters), as described by A.C. Bent in 1926, as well as R.P. Allen in 1952 and others in following decades. Whooping cranes tend to nest annually, but have been known to skip a year if they are nutritionally stressed or if nesting habitat conditions are unsuitable, as documented by F. Chavez-Ramirez and others in 1997 and later confirmed by B.W. Johns in 1998. The international recovery plan of 2007 clarified that there may also be other reasons that are not yet clear for this nesting behavior.
Each breeding pair has a territory defended primarily by the male, whose defense tactics may include running, flapping, hissing, stabbing or jumping and slashing with his feet, as described by Cornell University in 2019. Cornell University also noted that both parents incubate and brood-rear the young. One member of the pair remains on the nest at all times, with the exception of brief intervals. Females tend to incubate at night, as documented by R.P. Allen in 1952 and L.H. Walkinshaw later confirmed in 1965 and1973. Females also assume primary responsibility of feeding and caring for the young, as was documented by D.R. Blankinship in 1976. Parents and young return to the nest each night during the first three to four days after hatching; thereafter, parents brood their young wherever they are at night or during inclement weather. During the first 20 days after hatching, the parents and their young tend to stay within 1.1 miles (1.8 kilometers) of the nest site as observed by Ernie Kuyt and referenced in the international recovery plan of 2007. Doug Bergeson observed that their daily movements average 0.2 miles (340 meters), as further referenced in the international recovery plan.
Every two to three years, whooping cranes complete a full flightless molt of primary flight feathers, which makes them more vulnerable to predation threats and perhaps prompts them to change their habitat selection from open wetlands to areas with a higher concentration of cover, as noted by A. Lacy and D. McElwee in 2016.
Whooping cranes are a long-lived species, with current estimates suggesting a maximum longevity of at least 30 years for individuals in the wild, as documented by C. Mirande and others in 1993. A.F. Moody documented in 1931, and F. McNulty later confirmed in 1966, that captive individuals can live 35 to 40 years.
Species that may appear similar in appearance to whooping cranes include:
- American white ibis
- American white pelicans
- Great egrets
- Sandhill cranes
- Snow geese
- Wood storks
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