Whooping crane
Grus americana
SPECIES CODE: B003 V01
STATUS:
Listed endangered (32 FR 4001, 1967 March 11) except where nonessential experimental population (66 FR 33903-33917, 2001 June 26; 62 FR 38932-38939, 1997 July 21; and 58 FR 5647-5658, 1993 January 22) in Colorado, Indiana, Florida, New Mexico, Utah, and the western half of Wyoming. Recovery Plan completed on February 11, 1994.
SPECIES DESCRIPTION:
The whooping crane stands 5 feet tall and has a long, sinuous neck and long legs. Its snowy white body feathers are accented by jet-black wingtips and a red and black head with a long, pointed, beak. The whooping crane's wings measure about 7 feet across. The whooping crane is named for its call, which has been described as a shrill, bugle-like trumpeting.
REPRODUCTION AND DEVELOPMENT:
Whooping cranes feed and roost in wetlands and upland grain fields where they associate with ducks, geese, and sandhill cranes. Whooping cranes nest in marshy areas among bulrushes, cattails, and sedges that provide protection from predators as well as food. They eat insects, minnows, crabs, clams, crayfish, frogs, rodents, small birds, and berries. Whooping cranes usually nest once each year, normally laying two eggs in late April to mid-May, with hatching occurring about one month later. Survival is usually limited to one nestling. Parents share incubation and rearing duties, but females take the primary role in feeding and caring for the young.
RANGE AND POPULATION LEVEL:
Wild populations of whooping cranes utilize the Texas Gulf coast, including Aransas NWR, Texas, and Bosque del Apache NWR, New Mexico, and migration and staging areas through northeastern Montana, the western half of North Dakota, central South Dakota, Nebraska, Oklahoma, and east-central Texas, and the non-migratory population in Florida. There are five areas of Critical Habitat designated for the whooping crane, located in Idaho, Kansas, Nebraska, Oklahoma, and Texas, primarily on Federal and State wildlife management lands. These areas provide roosting, resting, and foraging habitat to the whoopers as they migrate between their breeding and wintering grounds.
The total population as of March 2002 stood at 397 birds, with 114 birds present in 3 primary captive breeding areas and 283 birds in the wild.
HABITAT:
The current nesting area within Wood Buffalo National Park, Canada is poorly drained and interspersed with numerous potholes. Wetlands vary considerably in size, shape and depth, and most possess soft marl bottoms. Wetlands are separated by narrow ridges which support an overstory of white spruce (Picea glauca), black spruce (P. mariana), tamarack (Larix laricina), and willows (Salix spp.), and an understory of dwarf birch (Betula glandulosa), Labrador tea (Ledum groenlandicum), and bearberry (Arctostaphylos uva-ursi). Bulrush (Scirpus validus) is the dominant emergent in the potholes used for nesting, although cattail (Typah sp.), sedge (Carex aquatilis), musk-grass (Chara sp.), and other aquatic plants are common (Allen 1956, Novakowski 1965, 1966, Kuyt 1976a, 1976b, 1981a).
Nest sites are being located in the rushes or sedges of marshes, sloughs, or along lake margins (Bent 1926). Allen (1956) found an abundance of invertebrates, primarily mollusks, crustaceans, and aquatic insects, in the ponds occupied by nesting pairs. He also encountered several species of minnows, frogs, and garter snakes (Thamnophis sp.), and believed that mollusks and frogs must be important items in the diet of breeding adults and their offspring.
Whooping cranes use a variety of habitats during migration (Howe 1987, 1989, Lingle 1987, Lingle et al. 1991), including croplands (feeding) and large palustrine (marshy) wetlands (roosting). Whooping cranes also roost in riverine habitat, most notably the Platte River, Middle Loup River, and Niobrara River in Nebraska; Cimarron River in Oklahoma; and the Red River in Texas (USFWS confirmed sighting records). Cranes roost on submerged sandbars in wide unobstructed channels that are isolated from human disturbance (Armbruster 1990).
About 9,000 hectares of salt flats on Aransas NWR and adjacent islands comprise the principal winter grounds. Marshes are dominated by salt grass (Distichlis spicata), saltwort (Batis maritime), smooth cordgrass (Spartina alterniflora), glasswort (Salicornia sp.), and sea ox-eye (Borrichia frutescens). Inland margins of the flats are dominated by Gulf cordgrass (Spartina spartinae). Interior portions of the refuge are gently rolling and sandy and are characterized by oak brush, grassland, swales, and ponds. Typical plants include live oak (Quercus virginiana), redbay (Persea borbonia), and bluestem (Andropogon spp.) (Stevenson and Griffith 1946, Allen 1952, Labuda and Butts 1979).
PAST THREATS:
Cranes disappeared as agriculture claimed the northern Great Plains of the U.S. and Canada (Allen 1952). Only one small population survived. Man's conversion of pothole and prairie to hay and grain production made much of the original habitat unsuitable for whooping cranes. Disruptive practices included draining, fencing, sowing, and all of the human activity associated with these operations. The advent of rural electrification brought power lines, and collisions are known to have accounted for the death or serious injury of at least 19 whooping cranes since 1956.
CURRENT THREATS:
Delayed sexual maturity, small clutch size, and low recruitment rate preclude rapid population recovery. The current northern breeding grounds may be another handicap to productivity because the ice-free season is only 4 months. During that time, pairs must incubate their eggs for 29-31 days, and rear their chicks to flight age in 3 months. Consequently, unless nest loss occurs early in incubation, there is rarely time to lay a second clutch and fledge young if the first clutch fails.
Whooping cranes are exposed to various natural obstacles and problems during migration. Snow and hail storms, low temperatures, and drought can present navigational handicaps or reduce food availability. Thus, migrating cranes are exposed to a variety of hazards such as collision with obstructions, predators, disease, and illegal shooting.
Hurricanes and drought can create problems on the wintering grounds. Fortunately, the hurricane season usually ends by October 31, before most whooping cranes arrive. A late season hurricane could place cranes at risk due to high wind velocities. Drought influences availability and abundance of the natural food supply by altering salinity of tidal basins and estuaries (Blankinship 1976). Bobcats (Lynx rufus) prey on young whooping cranes in Texas and Florida.
Whooping cranes adhere to ancestral breeding areas, migration routes, and wintering grounds. There is little likelihood of pioneering new habitat, except locally. The only self-sustaining wild population remains vulnerable to destruction through a hurricane or contaminant spill, due primarily to its limited wintering distribution along the GIWW of the Texas coast. The GIWW experiences some of the heaviest barge traffic of any waterway in the world. Much of the tonnage is in petrochemical products. An accident resulting in a spill could potentially destroy whooping cranes and/or their food resources. Transport of petroleum products and other chemicals by barge along the GIWW has for many years been considered a potential danger to whooping cranes and other wildlife at Aransas NWR.
CONSERVATION MEASURES:
LITERATURE CITED:
Allen, R. P. 1952. The whooping crane. National Audubon Society Resource Report 3,
246 pp.
Allen, R.P. 1956. A report on the whooping cranes' northern breeding grounds. National
Audubon Society Supplemental Resource Report 3, 60 pp.
Armbruster, M. J. 1990. Characterization of habitat used by whooping cranes during
migration. Biological Report 90(4):1-16.
Bent, A. C. 1926. Life histories of North American marsh birds. U.S. National Museum
Bulletin 135:219-231.
Blankinship, D. R. 1976. Studies of whooping cranes on the wintering grounds. Pages
197-206, in J. C. Lewis, ed. Proceedings International Crane Workshop. Oklahoma State University Press, Stillwater.
Howe, M.A. 1987. Habitat use by migrating whooping cranes in the Aransas-Wood
Buffalo corridor. Pages 303-311 , in J. C. Lewis and J. W. Ziewitz, eds. Proceedings 1985 Crane Workshop. Platte River Whooping Crane Habitat Maintenance Trust and U.S. Fish and Wildlife Service, Grand Island, Nebraska.
Howe, M.A. 1989. Migration of radio-marked whooping cranes from the Aransas-Wood
Buffalo population; Patterns of habitat use, behavior, and survival. U.S. Fish and WildI. Serv., Fish WildI. Tech. Rept 21, 33pp.
Kuyt, E. 1976a. Whooping cranes: The long road back. Nature Canada 5:2-9.
Kuyt, E. 1976b. The continuing story of the whooping crane. Pages 109-111 , in T.
Mosquin and C. Suchal, eds. Proceedings of a Symposium on Canada's Threatened Species and Habitats. Canada National Federal Spec. Publ. 6, Ottawa, Canada.
Kuyt, E. 1981. Population status, nest site fidelity, and breeding habitat of whooping
cranes. Pages 119-1 25, in J. C. Lewis and H. Masatomi, eds. Crane Research Around the World. International Crane Foundation, Baraboo, Wisconsin.
Labuda, S.E., and K.O. Butts. 1979. Habitat use by wintering whooping cranes on the
Aransas National Wildlife Refuge. Pages 152-1 57, in J. C. Lewis, eds. Proceedings 1978 International Crane Workshop, Colorado State University, Printing Service, Fort Collins, Colorado.
Lingle, G.R. 1987. Status of whooping crane migration habitat within the Great Plains of
North America. Pages 331-340 in J. C. Lewis and J. Zewitz, eds., Proceedings 1985. Crane Workshop. Platte River Whooping Crane Habitat Maintenance Trust and U.S. Fish and Wildlife Service, Grand Island, Nebraska.
Lingle, G.A. Wingfield, and J.W. Ziewitz. 1991.The migration ecology of whooping
cranes in Nebraska, U.S.A. Pages 395-401 in J. Harris, ed., Proceedings 1987
International Crane Workshop, International Crane Foundation, Baraboo, Wisconsin. Longley, W. H. 1970. Sandhill cranes at the Carlos Avery Wildlife Area. The Loon 4:124-128.
Novakowski, N. 5. 1965. The day we rescued a whooping crane. Audubon Magazine
67:230-233.
Stevenson, J.O., and R.E. Griffith. 1946. Winter life of the whooping crane. Condor
48:160-178.
U.S. Fish and Wildlife Service (USFWS). 1994. Whooping Crane Recovery Plan.
Albuquerque, New Mexico. 92 pp.
U.S. Fish and Wildlife Service (USFWS). 1993. Endangered and Threatened Wildlife
and Plants; Establishment of an Experimental Nonessential Population of Whooping Cranes in Florida. Federal Register. 58: 5647-5658.
U.S. Fish and Wildlife Service (USFWS). 1997. Endangered and Threatened Wildlife
and Plants; Final Rule to Designate the Whooping Crane of the Rocky Mountains as Experimental Nonessential and to Remove Whooping Crane Critical Habitat Designations From Four Locations. Federal Register. 62(139):38932-38939.
U.S. Fish and Wildlife Service (USFWS). 2001. Endangered and Threatened Wildlife
and Plants; Establishment of a Nonessential Experimental Population of Whooping Cranes in the Eastern United States. Federal Register. 66(123):33903-33917.