Why is whooping crane endangered

Individuals of one family group violate the assumption of spatial independence Millspaugh et al. Five individual whooping cranes with radiotransmitters were tracked across Nebraska over 4 years , Kuyt These five birds were tracked over Nebraska in seven fall and five spring migration passes. Because there is little evidence of fidelity for stopover sites among years or between seasons color-banded data above and Howe , multiple mi-.

The effective sample size of whooping cranes studied, for habitat selection purposes, is 12 not 18 or 27 or the number of migration passes made by radio-tracked birds over Nebraska. Specifically, one migration pass was tracked in , three in , five in , and 3 migration passes in Kuyt From to , no tracked whooping cranes stopped on the central Platte.

In comparison, no whooping cranes tracked or otherwise were seen on the Platte River during , , and , whereas eight sightings occurred in Appendix C.

The predicted portion of whooping cranes expected to stop at the Platte River in Figure a would be 2. Failure of tracked whooping cranes to stop at the central Platte during the early s, therefore, does not necessarily suggest that the central Platte is unimportant to whooping cranes. Two other factors might reduce the likelihood that whooping cranes with radiotransmitters will stop on the central Platte.

First, radio-tracked bird use of Nebraska was more frequent in spring than in fall Table 2 in Howe , p. Disproportionate sampling, coupled with a small sample size, would increase bias against observing stopovers on the central Platte.

Second, Austin and Richert describe a weak tendency for family groups stopping over in Nebraska to be found more frequently at locations away from the Platte River. Of the 12 migratory passes tracked, eight passes were made by family groups Kuyt , so additional bias against observed stopovers on the central Platte was possible. Radio-tracking data have provided much needed insight into habitat use and behavior during migration. These data suggest that cranes move rapidly through stopover areas Kuyt and use a variety of habitats for foraging and resting during stopovers Austin and Richert ; Howe It is apparent that weather events and migration behavior related to weather and climate may determine where a crane might stop during migration as much as the quality of a potential stopover habitat Kuyt Accordingly, it is difficult to assess how important individual stopover areas may be to individual cranes or to the AWP as a whole.

Lingle, University of Nebraska, unpublished material, March 22, 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.

Platte River at all. Conclusions of Pitts and Lingle should be taken with caution, however, because they are derived from data on just five whooping cranes that made a total of 12 flights over Nebraska at a time when the size of the AWP was less than half what it is now Figure Furthermore, the probability of any tracked crane stopping at the Platte was biased by the nonrandom grouping of experimental birds by social status a chick with parents vs a nonbreeding bird and by season fall vs spring.

More data on radio-tracked or satellite-tracked birds are clearly needed. Howe , Table 2 , in contrast, describes Nebraska as an important area for whooping cranes in spring.

If that is true, assessment of the importance of individual habitat areas must be carried out over sufficient periods to incorporate potential variations in conditions. The radio-tracking study examined whooping crane habitat use over a relatively short period 4 years and should be expanded temporally to include wider ranges of environmental conditions.

Assessment of central Platte River habitats should not be made independently of events in other regions. Relative importance of a given habitat to the population of a species of concern is typically measured by the degree to which that habitat is preferred by individuals of the population. Habitat suitability indexes therefore depend on habitat use in relation to habitat availability.

Assessments of the suitability of specific habitat characteristics for whooping cranes or the degree to which alternative habitats may be available to cranes now using areas of diminished quality begin by addressing issues of scale: within local habitats, within the home range of individuals, within the home range of the population, and within the entire geographic range of the species Johnson Researchers who fail to identify their scale of analysis may miss important relationships.

For whooping cranes, pertinent questions about habitat use in the central Platte River are connected to roosting Johnson ; Austin and Richert , although foraging in nearby wetlands is also important Lingle A number of reports have examined habitat selection for whooping cranes on all four scales.

Within habitats, night roosts have a number of physical characteristics believed to be important, including water depth and substrate profile Johnson ; Faanes et al. Within a. 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 Finally, within the geographic range of the species, they can select the state of Nebraska as a major location for stopovers in spring but may prefer Kansas and Oklahoma in fall Howe Austin and Richert summarized habitat evaluations at all known migration stopovers in the United States for whooping cranes from to On migration stopovers in Nebraska, whooping cranes typically use riverine habitats to roost at night and feed in upland usually agricultural or wetland habitats during the day.

Those findings represent descriptions of habitat that whooping cranes have actually used but do not represent use of habitats in relation to their availability or to randomly chosen habitats, so interpretation of the data on which they are based is limited. Foraging sites in wetlands tended to have characteristics similar to those of roost sites described below.

Water where whooping cranes foraged was shallower, on the average, than in the wetland as a whole. Physical characteristics within agricultural habitats used by foraging cranes were not evaluated, but these habitats also tended to be open and have short or no vegetation.

Several habitat assessments have focused on roost habitat characteristics. Johnson , p. Roost characteristics for used habitats are different from those for nonused habitats. Faanes et al. Roost locations for whooping cranes were more likely to be surrounded by deeper water than would be expected by chance alone. Few other studies have examined habitat selection on this geographic scale of selection.

Even though substantial data in both quantity and quality are available and reasonable habitat suitability models have been developed, the size of the AWP remains the chief limitation on analysis and interpretation. Such a small number of birds ensures that some high-quality sites inevitably.

For example, Faanes et al. However, the pattern of preference observed might not be the same if the number of whooping cranes using the central Platte were substantially larger. It is difficult to assess how much habitat in the central Platte will be adequate to support a viable delisted population of whooping cranes. Many reports indicate that the presence of forests is inversely related to the desirability of roosts. Whooping cranes use roosts where the width of unvegetated channel and the nonobstructed view of areas upstream and downstream of the roost are extensive Faanes ; Faanes et al.

Researchers, however, have yet to define specifically what constitutes a nonobstructed view for a whooping crane. Is the presence of a few trees enough to significantly alter use of an otherwise desirable open roost site? More experimentation could be done with habitat modification of forests in the river valley see Chapter 4. Debates about the appropriateness of forests in the Platte River Valley are mired, in part, because only two extremes forest vs open are presented where once an entire gradient of vegetation communities existed.

On a scale expanded to evaluate habitats within a home range, potential additional variables that might distinguish used from nonused habitat for whooping cranes include distance to nearest human development, distance from roost to feeding areas, and variety of habitats used Johnson ; USFWS, unpublished material, June 16, ; Austin and Richert No studies of habitat use by whooping cranes according to availability of those variables have been made; thus, their relative importance has not been quantified.

Foraging whooping cranes use both agricultural and wetland habitats throughout their migration Howe ; Austin and Richert , and this behavior differs from that of sandhill cranes, which strongly prefer agricultural habitats in Nebraska Iverson et al. Lingle et al. In the specific area of the central Platte, no extensive habitat-use studies have been done for foraging whooping cranes except that several authors characterize whooping crane foraging activities as parallel to sandhill crane preference for foraging in agricultural areas e.

From analysis on the scale of the Platte River Valley, more is known about use of roost habitats by whooping cranes. Within the valley, few whooping. Riverine roost sites are important whooping crane habitats throughout Nebraska Austin and Richert , not just on the central Platte. In Nebraska, and elsewhere in the flyway, wetlands not associated with the river also serve as important roosting habitats for whooping cranes in the AWP Austin and Richert Night roosts used by whooping cranes tend to be isolated from human disturbance and are within 1 mi of foraging sites.

The relative availability of nonriparian habitats is not known. In general, wetlands are important to migrating whooping cranes for both foraging and roosting. In the central Platte, use of riverine habitats by whooping cranes is well documented and appears important to their survival. Preference studies have not been done on this scale and, although useful, will be limited by the same problem of small population size as noted above.

Telemetry studies did not find riverine habitats important to roosting whooping cranes, however, because the few tracked birds primarily used palustrine wetlands Howe Bias occurred in both studies. Austin and Richert identified the limitations to analysis of habitat-use evaluations for migratory whooping cranes. Comparisons among sites are difficult because efforts to observe whooping cranes along the entire 4, km migration route are uneven.

Some regions are subject to underreporting Howe Still, the high incidence of use of riverine habitat by whooping cranes in Nebraska, compared with other states, is striking.

The quality of both palustrine and riverine habitats in Nebraska is high Stahlecker and, accordingly, these wetlands are used extensively by whooping cranes Austin and Richert With the opportunistic and nontraditional patterns of habitat selection exhibited by whooping cranes, it is difficult to predict habitat preferences on the scale of home ranges. Although nonhabitat variables such as weather events can influence habitat selection greatly Kuyt , the overall pattern of habitat use in Nebraska suggests that the general region of the central Platte including the Rainwater Basin is important to migrating whooping cranes.

On large time scales, as wet and dry periods cycle through the region, the interaction among the sites will probably be important Richert Whooping cranes will need stopover habitat during droughts when wetlands in the Rainwater Basin are dry and during wet years when the Platte River is above flood stage. Maintaining a complex of. Few data relevant to use of habitats by migrating whooping cranes on the largest geographic scale exist.

However, telemetry data reported by Howe suggest differences in use of stopover areas between fall and spring migrations. Whooping cranes appear to spend more time in Nebraska in spring than they do in fall Howe , Table 2, p. In fall, many whooping cranes tend to stop in a Saskatchewan staging area for several weeks before continuing their migration, presumably to acquire fat reserves for migration. It takes cranes about two daily flights to reach that region in Saskatchewan after leaving their breeding grounds in WBNP Kuyt After leaving Saskatchewan, the birds migrate rapidly and reach Nebraska in days and Texas in days more Kuyt During fall migration from to , several radio-tracked whooping cranes flew over Nebraska without stopping in the state at all Kuyt In spring, however, cranes do not use a staging area Kuyt Longer periods spent in Nebraska in spring may therefore be a function of proximity to ANWR as a starting point.

Collectively examining habitat selection for whooping cranes at all four geographic scales suggests that Nebraska, and the central Platte in particular, provide critical habitat for this species.

Climatic variations and development pressures likely over the next 30 years in which whooping cranes will need to recover assuming that current population trends continue will further emphasize the importance of providing stopover habitats for whooping cranes on the central Platte. Two basic ecological needs of migratory bird species are met by migration stopover or staging habitats: food and a safe resting place. Energy and nutrients are acquired and stored for use during future phases of the annual cycle see Alisauskas and Ankney The reserves can be used to provision future flight, allow birds to persist through periods of food shortage, or help to meet reproductive needs when exogenous food resources are insufficient.

Because energy and nutrient reserves are acquired in one stage of the annual cycle and used in another, mortality and natality can be influenced by events that occur in other stages of the annual cycle, producing a cross-seasonal effect Weller and Batt ; Fretwell Birds require safe environs at each habitat they visit. 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. When whooping cranes leave breeding areas at WBNP, they often fly for 2 or more days to reach a staging area in Saskatchewan, where they remain for a few days to a month Kuyt ; weeks is the average period of occupancy in this fall staging area. That winter there were whoopers in the wild and birds in captivity for a total world population of Whooping Cranes. The Whooping Crane is determined to recover, but the only way it can is if we protect its habitat.

The breeding area in Wood Buffalo National Park is protected, and part of the wintering land in Texas has been a wildlife refuge since Several migration stopover areas have since been protected in the US. Before , there were several captive breeding programs in the United States that used wild whooper eggs from Wood Buffalo National Park.

In , there were 95 whoopers in captivity. Since then, enough eggs are produced at the captive breeding sites that collecting wild eggs is no longer necessary. The Calgary Zoo remains the only captive breeding site for whoopers in Canada.

There have been several cross-fostering experiments, where whooper eggs are placed with other crane flocks. Unfortunately, the whoopers thus raised had difficulty breeding with other Whooping Cranes and so the practice has been stopped. Magazine How one image captures 21 hours of a volcanic eruption. Science Why it's so hard to treat pain in infants. Science The controversial sale of 'Big John,' the world's largest Triceratops.

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See how people have imagined life on Mars through history. They can also be found in upland areas, especially during migration. Courtship rituals are eccentric with the pair performing loud vocalizations, wing flapping, head bowing and leaps into the air. Whooping cranes mate for life. Two eggs are laid in a nest made of bulrush and other vegetation.

Incubation is about 29 days. Both parents incubate the eggs and feed the young. Usually only the larger chick survives due to its more aggressive behavior. Young cranes are capable of flight in about 90 days. Whooping cranes may live 20 years.