Stately, majestic, and charismatic, the Whooping Crane is a familiar symbol of the potential success of cooperative, international efforts to protect migratory species and of conservation laws such as the Migratory Bird Treaty Act and the U.S. Endangered Species Act. It is inarguably the most intensively managed and monitored boreal bird; every single individual is known, and usually its whereabouts as well. The species has been brought back from the brink of extinction through a combination of habitat protection, hunting control, captive breeding, and reintroductions and, though its numbers are still just a tiny fraction of what they once were, its future now seems relatively secure.

Habitat:

Historically, the Whooping Crane nested primarily in prairie marshes and in aspen parkland and boreal wetlands. The only surviving self-sustaining migratory population nests in Wood Buffalo National Park in Northern Alberta. The breeding grounds is an area of boreal spruce, tamarack, and willow forest growing on narrow ridges interspersed with shallow, bulrush-vegetated potholes. This population uses croplands and shallow, inland wetlands en route to its wintering grounds, where it uses estuarine marshes, shallow bays, and tidal flats in Texas at the Aransas National Wildlife Refuge.

Diet/Feeding Behavior:

Like most cranes (and many other birds), the Whooping Crane is omnivorous, its diet varying seasonally. It tends to be primarily carnivorous in the breeding season, eating a broad range of small, aquatic vertebrates and invertebrates along with a few tubers and berries. On migration, it consumes more vegetable matter such as tubers and waste grains. The winter diet is primarily coastal invertebrates, especially crabs and clams, supplemented with upland animals and acorns obtained from flooded or burned fields. It uses a variety of techniques, including plucking, probing, and stabbing, to procure food items; one study recognized 12 distinct feeding behaviors.

Breeding:

As with other cranes, the Whooping Crane has a low reproductive rate compared to most birds. This has contributed to its slow recovery. The birds begin pair bonding during their second or third winter; the process may take up to three winters while the birds associate in flocks of sub-adults. The birds remain paired until one dies, after which the other usually re-mates quickly. Pair bonding, which is repeated annually, consists of walking, calling, and dancing in unison; the dance includes spectacular vertical leaps with neck arched and wings flapping. Breeding usually begins at four years of age. Experienced pairs arrive on the breeding grounds in and around Wood Buffalo National Park, on the border of Alberta and the Northwest Territories, in late April, returning to their previous territories, which they defend vigorously against young pairs arriving later. The nest is a heap of vegetation with a shallow depression on top in which two eggs are laid. Both birds incubate, primarily the male in daytime and the female at night. The precocial young hatch in about a month and are brooded at night and during bad weather for several weeks, initially in the nest but subsequently elsewhere within the territory. The young are fed entirely by the parents at first and gradually learn to feed for themselves, though they continue to beg for months afterward. The chicks can fly well by about three months of age and reach adult size at about eight months. They migrate south with their parents the first time and remain with them through the first winter, usually returning with them to the breeding grounds. Young birds usually spend their first few summers near their natal area before beginning to breed, and migrate and winter together.

Migration/Winter Range:

In historic times there were both migratory and sedentary populations of this species. The surviving population migrates from Wood Buffalo National Park (when?) in northwest Canada first to southern Saskatchewan, where the birds rest and feed for several weeks. They then quickly travel down a narrow corridor, roughly along the 1000-m contour line, through Montana and the Dakotas, Nebraska, Kansas, and Oklahoma to the central Texas coast in the vicinity of Aransas National Wildlife Refuge for the winter. The northward route in spring is much the same. Occasional birds show up in adjacent states and some, mostly sub-adults, summer south of the winter grounds. Experienced birds take about 50 days to migrate south but only 10-11 days to migrate north.

Conservation Issues and Status:

The Whooping Crane originally nested from Illinois and Hudson Bay to Wyoming and the Northwest Territories and wintered from Texas and Louisiana to south-central Mexico, but it was never a common species. The highest total population estimate, in the 1860s, was only 1400 individuals (numbers probably had dropped already by that time). Intensive hunting and habitat destruction over the next 50 years almost wiped the species out; in the early 1900s, shooting alone probably exceeded reproductive potential. In 1937, only two small populations, one migratory and one sedentary, remained. By 1941, the migratory population was reduced to only 16 birds. Although its Texas wintering grounds were well known, resulting in the establishment of Aransas NWR in 1937, its remote breeding grounds were not discovered until 1954, 30 years after they were set aside for the protection of bison. Since then, eggs have been taken from wild nests for captive rearing and infertile wild eggs have been replaced with fertile ones. The last individual from the sedentary population was taken into captivity in 1950. The International Whooping Crane Recovery Team was established in 1985 with the goal of establishing new sedentary and migratory flocks. In 1993, a sedentary population was established in Florida from captive-reared birds; although the parents of these birds were migratory, migratory behavior in this species is learned, not innate. This population now numbers about 100. In 2000, another flock of captive-reared birds was taught to migrate from Wisconsin to Florida using ultralight aircraft to guide them; there are now about 40 birds in that population. Attempts in the 1970s and 1980s to establish an additional population nesting in Idaho and wintering in New Mexico, using wild Sandhill Cranes as foster parents, failed because of sexual imprinting problems among the young Whooping Cranes. The Wood Buffalo population now stands at nearly 200 individuals and is expected to reach 1,000 by 2033 at its current rate of growth. With over 100 birds in captivity in several locations, the total world Whooping Crane population has rebounded to over 400. Although the species now seems secure, there is still only one self-sustaining population, which could be wiped out by a single oil spill, forest fire, or disease outbreak. Thus, the establishment of additional flocks is essential to the future well-being of the species.

References:

• Allen, R. P. 1952. The Whooping Crane. Natl. Audubon Soc. Resour. Rept. 3, New York.
• Allen, R. P. 1956. A report on the Whooping Cranes’ northern breeding grounds. Natl. Audubon Soc. Suppl. Resour. Rept. 3, New York.
• Armbruster, M. J. 1990. Characterization of habitat used by Whooping Cranes during migration. Biolog. Rept. 90(4):1-16.
• Bishop, M. A., and D. R. Blankinship. 1982. Dynamics of subadult flocks of Whooping Cranes at Aransas National Wildlife Refuge, Texas, 1978-1981. Pp. 180-189 in Proc. 1981 internatl. crane workshop (J. C. Lewis, ed.). Natl. Audubon Soc., Tavernier, FL.
• Ellis, D. H., G. W. Archibald, S. R. Swengel, and C. B. Kepler. 1991. Compendium of crane behavior. Part 1: individual (nonsocial) behavior. Pp 225-234 in Proc. 1987 internatl. Crane workshop (J. Harris, ed.). Internatl. Crane Found., Baraboo, WI.
• Lewis, J. C. 1995. Whooping Crane (Grus americana). In The Birds of North America, No. 153 (A. Poole and F. Gill, eds.). The Academy of Natural Sciences, Philadelphia, and The American Ornithologists’ Union, Washington, D.C.
• Whooping Crane Conservation Association Web site, http://www.whoopingcrane.com