Endangered and Threatened Species of the Platte River (2005) / Chapter Skim
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5 Whooping Crane
5 Whooping Crane
Pages 155-185
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From page 155... ...
Is the current designation of central Platte River habitat as critical habitat for the whooping crane supported by existing science? In addressing those questions, this chapter reviews relevant databases, examines the use of the central Platte habitat by whooping cranes, and evaluates the influence of the habitat on population parameters, including mortality, natality, and distribution.
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From page 156... ...
. Wetland ecosystems historically used by wintering whooping cranes were diverse as Gramma-Grass -Antelope Biome Prairie-Aspen Parkland Belt Former Breeding Areas Former Wintering Areas Main Migration Routes Occurrence Beyond Principal Range FIGURE 5-1 Historical distribution of whooping cranes in North America.
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From page 157... ...
A population that bred further west of Manitoba and wintered in Texas (whose remnant is the extant, migrating population) is thought to have passed through the region of the central Platte River and other portions of central Nebraska (Allen 1952)
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From page 158... ...
b. FIGURE 5-2 Distribution of whooping crane sightings in Nebraska.
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From page 159... ...
Source: CWS and USFWS, unpublished material, 2003.
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From page 160... ...
. USFWS identified the central Platte River as critical to protect "so that it would not be lost to development before its overall significance to whooping cranes could be determined" (Johnson 1982, p.
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From page 161... ...
have also suggested that inasmuch as the AWP continues to increase, stopover habitats used by whooping cranes during migration cannot be limiting the species. No data indicate that any specific habitat related to a particular stage of the annual cycle is generally limiting the AWP (CWS and USFWS, unpublished material, May 2, 2003)
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From page 162... ...
Allen concluded that Nebraska was important for migrating whooping cranes and that the central Platte River (which he referred to as the Big
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From page 163... ...
. The distribution of cranes shot on the central Platte River reflects historical use of local habitats, much of it on the river itself (Allen 1952, p.
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From page 164... ...
Observers at each stopover site also communicate as the birds continue moving north. Providing further continuity, Wally Jobman has coordinated whooping crane sightings for the Platte River region and
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From page 165... ...
In both seasons, potential observers are numerous and well distributed along the central Platte River. Nongovernment observers have contributed observations at the Rowe Sanctuary since 1975, as have the Whooping Crane Trust staff since the early 1980s.
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From page 166... ...
of whooping cranes, number of whooping crane sightings on the Platte River, Nebraska, and the number of sighting days (number of birds times number of days seen) on the Platte River, 1950 to 2002.
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From page 167... ...
It may be that as the AWP continues to increase, visitation rates of the entire population to the central Platte River change. Subadults, birds that have adult plumage but are incapable of breeding (Lewis 1995)
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From page 168... ...
94) related an interview that described whooping cranes as using the central Platte River for longer periods when overall population numbers were higher.
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From page 169... ...
Ratio of Numberof WhoopingCrane Use-Days on Platte River to y = 0.01518x - 30.02002 Total Wild Populationof Whooping Cranes R 2 = 0.3594 0.9000 0.8000 0.7000 Ratio 0.6000 0.5000 Use le 0.4000 iabraV 0.3000 0.2000 0.1000 0.0000 1976 1978 1980 1982 1984 1986 1988 1990 1992 1994 1996 1998 2000 2002 Year FIGURE 5-6 (a) Number of whooping cranes sighted at Platte River divided by total number of birds in Aransas-Wood Buffalo population (AWP)
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From page 170... ...
That low proportion of repeat sightings of the same birds on the central Platte River suggests that little fidelity to this stopover site occurs. Radio-tracked Birds In the early 1980s, after extensive experimentation on sandhill cranes, scientists fitted whooping cranes with radio-transmitters and tracked them during fall and spring migration (Kuyt 1992; Howe 1989)
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From page 171... ...
Lingle, University of Nebraska, unpublished material, March 22, 2000) used radiotelemetry data from migrating cranes to argue that habitats on the central Platte River are not critical to whooping cranes, inasmuch as birds that stop at the Platte could readily use other habitats if the Platte River were not available and most whooping cranes appeared not to use the central
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From page 172... ...
For whooping cranes, pertinent questions about habitat use in the central Platte River are connected to roosting (Johnson 1982; Austin and Richert 2001) , although foraging in nearby wetlands is also important (Lingle 1987)
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From page 173... ...
. Within the home range of a population, they can select for stopover areas between larger regions, such as the central Table Playas as opposed to the central Platte (Richert 1999)
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From page 174... ...
. Of whooping crane groups that stayed in the Platte River Valley for more than 1 day, 91% used channel areas as roost habitat (USFWS, unpublished material, June 11, 2003; Appendix C)
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From page 175... ...
Migration stopover sites in Nebraska include the central Platte River, Rainwater Basin, central Table Playas, and northern Sandhills (Richert 1999; USFWS, unpublished material, June 16, 2000; Austin and Richert 2001)
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From page 176... ...
Protection from natural predators and relative isolation from human activities contribute to the utility of stopover sites. The central Platte River has historically filled both needs for whooping cranes during their migrations.
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From page 177... ...
used behavioral descriptions and energetic models to conclude that whooping cranes regain fat reserves in winter areas before beginning their spring migration. They migrate back to WBNP relatively quickly, using stopover habitats en route but no staging areas.
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From page 178... ...
It is possible that spring migration areas could be used in new ways by whooping cranes. This possibility cautions against underestimating the ecological value of stopover habitats to whooping cranes, especially stopover habitats on the central Platte River.
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From page 179... ...
Would these shifts alter mortality? Migrating whooping cranes use wetlands near the central Platte River in the Rainwater Basin south of the river or in the central Table Playa to the north (Richert 1999)
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From page 180... ...
In this context, relating the fitness of individual birds or the likely persistence of the population to central Platte River habitat conditions is tenuous. Nonetheless, three PVAs for whooping cranes are available and warrant consideration in conservation planning for the species.
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From page 181... ...
. Because there is no full-time resident or breeding population of whooping cranes in the Platte River Basin, conclusions about the role of the central Platte River in the persistence of the population must be based on some stringent assumptions, including the assumption that the loss of Platte River habitat will result in some increase in mortality or other contribution to decreased fitness of the population.
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From page 182... ...
Without central Platte River stopover habitats, alternative habitats elsewhere in the migratory pathway will be necessary to provide resources for dispersing whooping cranes. TABLE 5-1 Results of Scenario 3 Simulations Of Populations that Do Of Populations that Initial Size Not Go Extinct, Mean Go Extinct, Mean of Extinction Population Size at Time to Extinction, Population Probability Target Time years Baseline: maximal age, 50 years 18 0.098 1,305 51 185 0.005 1,360 133 Maximal age, 40 years 18 0.113 1,267 55 185 0.008 1,345 117 Maximal age, 30 years 18 0.126 1,253 60 185 0.006 1,344 80 Source: Reed 2003.
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From page 183... ...
The committee concluded that current habitat conditions along the central Platte River adversely affect the likelihood of survival and recovery of the whooping crane population. Geographically, the central Platte River occupies a critical position along the migration route of the species, between the wintering grounds in coastal Texas and the summer breeding grounds in north central Canada.
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From page 184... ...
If mortality increases by only 3% -- a likely scenario if the Platte River habitats become unavailable, because most crane deaths occur during migration-the entire migrating population of less than 200 is likely to become unstable. The general total population of migrating whooping cranes is slowly increasing from its low of only 15 in 1941, and the proportion of the population that uses the central Platte River as a stopover each year is also gradually increasing.
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From page 185... ...
When managers clear woodland for whooping crane habitat, for example, there appear to be favorable outcomes for the crane population, but there is little knowledge about the effects of such actions on other species, so continued monitoring and measurement efforts are required. The committee also recognizes the importance of long-term records and data in reaching conclusions about whooping crane use of the central Platte River.
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