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High horns, low horns, silence, and finally a pandemonium of trumpets, rattles, croaks, and cries that almost shakes the bog with its nearness, but without yet disclosing whence it comes. At last a glint of sun reveals the approach of a great echelon of birds. On motionless wing they emerge from the lifting mists, sweep a final arc of sky, and settle in clangorous descending spirals to their feeding grounds. A new day has begun on the crane marsh....Our ability to perceive quality in nature begins, as in art, with the pretty. It expands through successive stages of the beautiful to values as yet uncaptured by language. The quality of cranes lies, I think, in this higher gamut, as yet beyond the reach of words.
-- Aldo Leopold, A Sand County Almanac,1949

What could one add that might better capture the wildness and magnificence of sandhill cranes? If you have not seen the great spring concentration of cranes along the Platte River in Nebraska, you should do so. It is one of the world's great spectacles of animal migration and it provides an indelible experience on many levels. The visual and aural immensity of it saturates the senses. At the same time, it is interesting and important to understand the dynamics of the phenomenon, the driving but often subtle interactions between human activities and those of the cranes. The detailed, long-term studies by Gary Krapu and his colleagues reveal that the cranes are not only dancing with one another; they are enjoined by fate to engage in an extended pas de duex with us, and that the dance has just begun. Whether they will still mass on the Platte a hundred or a thousand years from now is largely in our hands.-K.P.A.

There are few places as captivating in early spring to a student of bird migration as the Platte River Valley of south-central Nebraska between Grand Island and Kearney. Here, at dawn from mid- to late March, one can view thousands of sandhill cranes departing their roosts located in channels of the Platte River (Plate 7.1) or in nearby fields during the rest of the day. Moreover, cranes are often close to roads, offering one of the best opportunities on the continent for viewing this usually wary bird. For me, spending time among the cranes in spring is special because the species has lived in what is now Nebraska for more than one million years. Listening to sandhill cranes and observing their behavior, one is left contemplating conditions in the Pliocene that would have fostered the evolution of such a bird.

My first visit to the Platte was in the early spring of 1978. I had agreed to serve as project leader for the Platte River Ecology Study which the U.S. Fish and Wildlife Service had undertaken to gain insight into habitat requirements of migratory bird populations using the Platte River Valley, and particularly of sandhill cranes[1,2]. Intrigued by the species migratory habits, I wanted to know a) why nearly 80% of all sandhill cranes in North America gather along the Platte and North Platte Rivers in spring, and b) habitat needs during their stay. In this chapter, I draw upon information gained from my research and from that of my colleagues to identify underlying factors responsible for the current springtime staging pattern of sandhill cranes in the Platte River Valley. I conclude with a description of efforts underway in the Platte River Valley to protect the habitat that supports sandhill cranes and other waterbirds and, in that context, I discuss our information needs.

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Table of Contents

• The Great Plains, a Landscape in Transition
• The Introduction of the Mechanical Cornpicker
• Increasing Corn but Shrinking Channels
• Seeking Answers
• Learning How to Capture Cranes
• Habitat Preferences
• Feeding Ecology
• Refueling for Migration and Reproduction
• Implications of a Changing Landscape
• Shrinking Channels, a Growing Problem
• Working Toward a Solution
• References
• Acknowledgements

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The Great Plains, a Landscape in Transition

Until the late 19th century, the area known as the Central Plains was a vast prairie wilderness. The fertile Platte River Valley with its subirrigated meadows and wide channels attracted great herds of bison and an abundance of migratory waterbirds in spring. The wide channels of the Platte were a favored roosting area for sandhill cranes during their northward migration. Before agriculture and crop residues, food availability was variable from year to year and cranes were more opportunistic in their migratory habits. Thus flocks were more dispersed than in modern times, and stopovers were probably of shorter duration.

Up to 1850, the Great Plains remained sparsely inhabited, mostly by Indian tribes which represented the last in a long line of hunters and gatherers that had occupied the plains during the postglacial period (10,000-12,000 years and possibly longer). At low population densities and carrying primitive weapons, humans inhabiting the region before the mid-19th century likely had little effect on sandhill crane populations that nested in or migrated across the central and northern Great Plains.

Cataclysmic change in the prairie ecosystem began in the third quarter of the 19th century. Treaties that had left large parts of the Great Plains in a natural state under the control of indigenous tribes were broken as political pressure mounted to open the region to white settlers, miners, and others. Confiscation of Indian lands was backed by military force in the 1860s and 1870s, ending the nomadic life of the Plains tribes. This action set the stage for the arrival of millions of homesteaders and for agricultural development of the Great Plains that would profoundly affect the distribution and habits of sandhill cranes in the coming century.

Sandhill cranes, because of their large size, were particularly vulnerable to hunting during settlement of the Great Plains between 1880 and 1910. Although habitat remained plentiful for cranes, without laws to control hunting and with a lack of sanctuaries the Plains breeding population was decimated by the turn of the century. Northern-nesting populations fared better but their numbers also declined.

Concerns raised by the decline of many species of waterbirds owing to uncontrolled hunting led to the introduction in Congress in 1904 of legislation to place migratory birds under federal protection. After nearly a decade of intense lobbying by conservation leaders, the Migratory Bird Act was passed by Congress and signed into law by President Taft on 4 March 1913. In 1916, the Migratory Bird Treaty between the United States and Canada was ratified for Canada by Great Britain, expanding protection for sandhill cranes, waterfowl, and many other species to a large part of North America. The U.S. Biological Survey was given responsibility for enforcing the treaty.

With the gradual decline of uncontrolled hunting, the midcontinent sandhill crane population began to rebound. The recovery was aided by the severe drought and Great Depression of the 1930s which reduced human densities markedly across large areas of the Great Plains. National wildlife refuges (NWRS) were being established in most states on the Central Flyway, providing additional protection for sandhill cranes[3].

The Introduction of the Mechanical Cornpicker

Agriculture had provided some food for sandhill cranes from the onset of farming in the late 19th century, but handpicking of corn and threshing of other crops left little grains in the fields after harvest. By the early 1940s, though, mechanical cornpickers were replacing human laborers for harvesting corn in the Great Plains and leaving from 6% to 8% of the crop in the fields, creating an abundant food supply for cranes and other wildlife. As corn residues increased in the North Platte and Platte valleys close to favored channel-roosting habitat, the number of migrant flocks of sandhill cranes stopping increased as did the length of their stay. In the spring of 1943, an estimated 100,000 sandhill cranes stopped in the North Platte River Valley. Farmers made no effort to chase the growing numbers of cranes from their fields or disturb them on their roosts, for the birds posed no threat to their farming operations.

Corn availability to cranes grew from the 1940s through the 1970s as yields increased. By 1950, most of the corn in the Platte River Valley was being harvested by mechanical cornpicker. From 1956 to 1979, corn yield and availability to cranes and other wildlife in Nebraska increased fivefold, mostly because of the growing use of irrigation, greater input of fertilizer, and the development of hybrids capable of producing high yields. By the late 1970s, most of the cropland in the Valley was in corn, nearly all the corn was irrigated, and corn residues were abundant.

Increasing Corn but Shrinking Channels

The growing abundance of corn residues in the Platte River Valley as a result of the mechanization of agriculture was coupled with a dramatic decline of roosting habitat in channels of the upper and central Platte River and elsewhere along their migration route, starting in the 1940s [4]. Historically, the Platte River ecosystem was maintained primarily by runoff from the western plains and eastern slope of the Rocky Mountains which was carried through the North Platte and South Platte rivers. By late summer, early accounts indicated, flows in the upper and central Platte River were but a small fraction of spring flows. The combination of spring flooding and summer drying of much of the channel kept sandbars unstable and mostly free of vegetation, thus helping to maintain a wide, shallow, and braided channel. Although trees were already present on some islands in the river channel in the early 19th century, explorers' reports indicated a general lack of trees on the banks. In 1813, Robert Stuart, who was exploring the North Platte River, noted in his diary that, except for a lone tree, no timber existed on the north side of the river for 200 miles upstream from it's confluence with the South Platte River[5]. In 1865, Union Pacific Railroad surveyors reported that the channel width of the Platte River varied from about 770 to 1,870 yards between the confluence of the North and South Platte rivers and where Grand Island is located today[4]. As late as 1938, the channel remained wide through most of the upper and central Platte. At Overton, for example, the channel width was 1,672 yards (1,520 meters), only 99 yards (90 meters)less than in 1865.

Map 7.1 The changing distribution (shaded area) of spring-staging sandhill cranes in the North Platte and Platte river valleys over the past half-century. Because of a progressive narrowing of channels from west to east, starting at the confluence of the North Platte and South Platte rivers, cranes have abandoned much of the channel between Overton and Kearney and all of the Platte River upstream of where return flows from Tri-County Canal discharge back into the river near Overton. (Photo by G. Krapu)

Channel width began to shrink precipitously after Kingsley Dam was completed in 1941 on the North Platte River in western Nebraska, creating Lake McConaughy. For purposes of irrigation and power generation, most of the Platte River flows from just below the confluence of the North Platte and South Platte Rivers to near Overton were rerouted into the Tri-County Canal (Map 7.1). As a result, most of the active channel bed for 61 miles downstream to near Lexington became woodland over the next two decades. By 1980, a mile wide swath of maturing riparian woodland marked the route of what had been the channel of the upper Platte River (Fig. 7.1). The river channel remained wider downstream from Overton where return flows from the Tri-County Canal reentered the river, but the channel width was still less than 20% of what it had been in 1938.

Figure 7.1 The former width of the Platte River channel of Kearney, Nebraska, is indicated by this corridor of woodland. Channel width in nearly all of the upper Platte River and in large sections of the central Platte has been reduced by at least 90% and can no longer support cranes. (Photo by J. Eldridge)

As river channels narrowed, sandhill cranes gradually abandoned all of the upper Platte River Valley above where return flows from the canal reentered the river. Lawrence Walkinshaw, the first biologist to study sandhill cranes extensively, saw only 7 cranes between Cozad and North Platte in 1953 and none in 1954 when he visited the Platte and North Platte rivers [6]. Cranes still occupied the section between Cozad and Lexington in the late 1950s, but by the 1970s the entire reach from the confluence downstream to Lexington had been abandoned.

With loss of the upper Platte, cranes became separated into 3 staging groups, one is located on the 71-mile section of the central Platte between Overton and Chapman, a short distance east of Grand Island; another is situated upstream in a 30-mile section of the North Platte River to the west of the city of North Platte; and a third is at the upper end of Lake McConaughy (see Map 7.1). Sandhill cranes staging in the Platte Valley are of 3 subspecies, the largest being Grus canadensis tabida (greater), followed by G. c. rowani (lesser), and the smallest G. c. canadensis, the smallest. The breeding grounds of these races remain poorly defined, but the midcontinent population of G. c. tabida is thought to breed in northern Minnesota, southwestern Ontario, and adjoining areas in Manitoba. G. c. rowani presumably breed across a wide area of central Canada[3], but racial composition across much of the region remains poorly defined. Lesser sandhill cranes breed at higher latitudes in the central and western arctic, but little is known concerning the southern limits of their breeding range.

Seeking Answers

Loss of the upper Platte River Valley as a springtime staging area for the midcontinent sandhill crane population and declining channel width downstream from Overton to Grand Island had, by the 1970s, raised widespread concern that cranes and other migratory waterbirds were about to be displaced from the Platte River, with unknown consequences to these populations. This concern, and continuing expansion of irrigation development, resulted in a growing national debate over water policy issues involving the Platte River Basin. Responding to issues that had been raised, the U.S. Department of the Interior requested and received funds from Congress in 1977 to begin a major study to assess water needs of migratory waterbirds and man in the Platte River Basin, culminating in The Platte River Ecology Study.

Learning How to Capture Cranes

As a starting point for determining habitat needs of sandhill cranes during the staging period, I decided to radio-mark and systematically monitor individual cranes during their spring stay. Field work began in late February 1978, shortly after cranes started to arrive. Recognizing that capturing cranes would be difficult in late winter, I sought the expertise of Charlie Shaiffer, a biologist experienced in live-trapping waterbirds. We also drew insight from the work of Federal Game Management Agent Robert Wheeler, who had successfully trapped sandhill cranes in the Platte Valley a decade earlier. Our strategy was to lure the cranes to decoys in open fields where well-camouflaged cannon nets would, at the detonation of powder charges, be propelled over the unsuspecting cranes before they could take flight.

Despite taking numerous precautions, we were not prepared for the level of wariness shown by the early-arriving flocks, and our first trapping attempts ended in total failure. Flocks entering fields where our wooden decoys had been carefully positioned not only shied away, but in some cases flew low and carefully inspected the wire that led back to the observation blind used for setting off the charges. With our research program in jeopardy, we decided to move on to plan B: the use of taxidermy mounts as decoys. The only problem was that we had no mounts, prompting a widespread search for mounted cranes. As no one was about to lend us their prized specimens when they learned of our intent, the mounts we were given were a bit bedraggled (Plate 7.2). To our great relief, however, cranes seeing their own kind, notwithstanding a somewhat disheveled appearance, lowered their guard, and trapping operations to begin in earnest.

Habitat Preferences

Once cranes had been radio-marked, trackers working from antenna-equipped vehicles began systematically driving the roads of the study area, stopping at regular intervals to listen for the frequencies of transmittered cranes. (The frequencies had been programmed into the memory of the trackers multichannel receivers.) Trackers attempted to locate each crane once per hour, from early morning before the cranes left their roosts until dusk when the birds returned. Each location was established by triangulation of bearings from the nearest roads. When our monitoring of radio-marked cranes had ended and analyses were completed, we were able to determine that the birds were dividing their time mostly among cornfields (60%), native grassland (28%), and alfalfa hayland (9%). For reasons unknown, cranes were using native grassland and planted hayland more than we had expected.

To gain insight into this higher than expected use of grassland and hayland, we systematically monitored the cranes' activity by habitat type, using standard time-budget techniques. We found that the amount of time cranes spent searching for food varied by habitat, increasing from 20% in cornfields to 30% in native grassland to 44% in alfalfa hayland. From this pattern, we concluded that the foods cranes were seeking in native grassland and haylands required a greater foraging effort, leading to a disproportionate amount of time being spent in those habitats. During migration, sandhill cranes roost in a variety of sites including braided river channels, wet meadows, shallow lakes, and uplands. In the Platte River Valley, early-arriving cranes roost on ice in the river channel or on the frozen meadows when required, but they shift to shallow waters of the channel when possible. Cranes prefer roosting on submerged sandbars in channels greater than 165 yards wide (150 m) and avoid channels less than 55 yards wide (50 m) [7]. Vegetation height on riverbanks and on islands also influences roosting distribution when the channel width is less than 165 yards (150 m). The preference of cranes for wide channels probably is associated with greater security from predators and other forms of disturbance, security that presumably is particularly important where flocks stage for prolonged periods. Human activity near the river channel also affects crane use. Cranes avoid sections of river that are near bridges and roads. Less than half as many cranes roost in river segments where there are bridges, adjacent roads, or both than in segments without these features. Distribution of wet meadows also influences staging distribution of sandhill cranes in the North Platte and Platte river valleys. Humans, then, through a variety of actions affecting the landscape of the Platte River Valley and the Great Plains, have strongly influenced the current distribution of cranes and have made the birds' continued presence contingent on active habitat management.

Feeding Ecology

Corn, to no one's surprise, dominated the crane diet in cornfields, but the finding that cranes were feeding almost exclusively on macroinvertebrates in native grassland (including wet meadows) was unexpected (Plate 7.3). Earthworms were the dominant animal food taken in both grassland and alfalfa hayland, followed by insects. Snails accounted for nearly 25% of the diet in grassland, but less than 5% in hayland. We concluded that cranes had to forage on invertebrates in native meadows and hayland to obtain protein and calcium; corn, while an excellent source of energy because of high carbohydrate content, is deficient in those nutrients.

By the 1970s, corn residues were sufficiently abundant to support the needs of nearly the entire midcontinent sandhill crane population as well as large numbers of waterfowl during early spring. Ken Reinecke, a member of the Platte River Ecology Study team, measured corn availability in the fields (Plate 7.4) and found that, on average, about 8% of the standing crop of corn (of which about 25% was shelled kernels) remained in the fields after harvest. Although cattle were turned into many of the fields for fattening during the fall and winter, most of the shelled kernels remained available for waterfowl and cranes. We estimated that a population of about 500,000 cranes would remove about 1,471 metric tons of corn each spring to meet its needs. the amount represented only about only about 23% of the corn available in fields when the cranes arrived in early spring. As cropland area and corn acreage increased in the 20th century in the Platte River Valley, areas of native grassland and wet meadows diminished and macroinvertebrates declined resulting in a marked disparity between availability of high energy corn and protein-rich macroinvertebrates. In the 1970s, cranes we monitored spent as much time each day obtaining the estimated 3% of their diet formed by macroinvertebrates as they did obtaining the 97% of dietary corn. Conspicuous blackened patches on meadows and haylands reflected the intense foraging effort being put forth by cranes probing into the soils in search of soil invertebrates.

Refueling for Migration and Reproduction

Sandhill cranes are lean on arrival in the Platte River Valley in late February and early March. In the late 1970s, we found that lesser sandhill cranes weighing about 3,000 grams (6.6 pounds) on arrival acquired about 500 grams (1.1 pounds) of fat during their spring stay. After leaving the Platte in early April, the birds stored still more fat during stopovers at the northern edge of the Great Plains in prairie Canada. By the time lesser sandhill cranes arrived on the breeding grounds in the Yukon-Kuskokwim Delta in western Alaska, we found, fat reserves equal to the fat acquired in the Platte River Valley were still present. Thus, the pound of fat acquired in the Platte River Valley provided a major nutrient source for reproduction. Juveniles acquired less fat than adults, despite high corn availability, possibly because juveniles spend more time searching for macroinvertebrates in grasslands and haylands and, as nonbreeders, probably require less fat.

Implications of a Changing Landscape

Although corn converted to fat has both fueled the migration and provided a major part of the reproductive energy requirements of midcontinent sandhill cranes throughout the second half of this century, there is no guarantee that corn residues will remain adequate to meet these needs in the future. In fact, changes in staging behavior and other evidence suggests that corn residues and fat storage rates are in decline. In the late 1970s, cranes met their energy needs mostly within 2 or 3 miles of the Platte River; by the 1990s, cranes were ranging several miles beyond the valley to feed, an uncommon sight two decades ago. Thus, when a blizzard killed 2,000 cranes in the Platte River Valley in March 1996, I measured the body mass of the storm-killed sandhill cranes and found that body mass of the Canadian race had fallen substantially from similar measurements I had taken during 1978 and 1979. Body mass also averaged lower in the lesser sandhill cranes, but the differences were not statistically significant.

Because fat levels of storm-killed cranes may not have been representative of the population, I initiated new studies in the Platte River Valley in spring 1998 to confirm or refute the hypothesis that fat storage rates had declined over the past 2 decades and, if so, why. Preliminary results from these studies confirm that the fat storage rate may have declined as much as 50% from the 1970s. Although the underlying causes for reduced fat storage are still not known, lower corn residues are probably the main reason for the declining rate of fat storage.

More efficient corn-harvesting methods than those used in the past, growing competition from springtime-staging midcontinent Arctic-nesting geese, and an increase in the number of sandhill cranes present in spring are the most likely factors responsible for declining fat storage rate among cranes. From the various data sets we are acquiring under current studies, a mathemathical model will be developed to predict number of sandhill cranes that can be supported in the Platte River Valley under current management practices and alternatives. The model will offer cranes managers a new tool to help then make decisions on how best to manage lands for the sandhill crane population.

The causes and possible effects of declining fat storage rates on midcontinent cranes are still under study. A decline in fat reserves would be expected to have greater adverse consequences for those cranes having the longest migrations and for those breeding in the most extreme environments, where food is least available early in the breeding season. However, based on body mass measurements from 1996, fat reserves of the smaller-bodied and northern-nesting lesser sandhill cranes may have been affected by changing habitat conditions in the Platte River Valley than have fat reserves of the larger subspecies, which breed farther south under less severe conditions.

Recent declines in rate of fat storage in the Platte River Valley underscore the potential risk of species becoming inextricably linked to agriculture. Many species, like the sandhill crane, have become dependent on grain residues to meet their energy and fat storage needs during much of the year as native habitats that formerly supplied their needs have disappeared (Plate 7.5). For species deriving energy and fat storage needs from agricultural foods, the long-term outlook is uncertain because numerous factors can and are diminishing availability of agricultural foods. Moreover, it is unlikely that agriculture will return to less efficient harvesting methods such as those which existed in the recent past. Thus, species such as sandhill crane which have highly specialized roost-site requirements that limit their flexibility to adjust to changes in distribution and abundance of food are most likely to require human intervention to ensure needs are met.

Shrinking Channels, a Growing Problem

In the late 1970s, the midcontinent population of sandhill cranes roosted in about 51 miles (82 km) of the Platte River channel between Lexington and Chapman, a marked decline from the approximate 120 miles (193 km) of river available to cranes between the North Platte-South Platte confluence and Grand Island earlier in the century. By 1996, sandhill cranes were restricted to staging along a) approximately 40 miles (64 km) of the Platte River, b) the North Platte site near Sutherland, and c) a small area at the upper end of Lake McConaughy (see Map 7.1). Much of the Platte River to the west of Kearney has been abandoned or has limited use by cranes. Continuing shrinkage of crane roosting habitat in the Central Platte Valley is causing crane density and competition to increase, contributing to foraging farther away from the river and higher energy costs. The disproportionate amount of time cranes spend searching for invertebrates in wet meadows and grasslands despite declining fat storage rates suggests that they are having difficulty meeting their protein and/or calcium needs under current conditions; indirectly, that difficulty may be contributing to the declining rate of fat storage.

Trends and scale of habitat change in the Platte River Valley in the past 60 years raise the concern that the midcontinent sandhill crane population and other waterbirds could lose this key staging area sometime in the 21st century (Plate 7.6). Such a loss would have eliminated the best site on the planet for viewing large numbers of cranes and would bring to an end the annual visits of thousands of birders who come from across the United States and from other countries to see the cranes and other wildlife. Loss of the Platte River staging area would have unknown but potentially severe adverse consequences for the midcontinent population of sandhill cranes, which depend on this ecosystem for a major part of their nutrient needs for spring migration and reproduction.

The Platte River has been a strategic staging area for migrant waterfowl in a part of the Central Flyway that has lost much of its wetland resources to agricultural development. In the Rainwater Basin Area (RBA), a key Central Flyway waterfowl staging area adjacent to the Platte River Valley on the south, fewer than 400 of the original 4,000 wetland areas remain. As a result, crowding of waterfowl occurs in dry and unusually cold springs, and several hundred thousand ducks and geese have died due to epizootics of avian cholera during the past 25 years. In March 1998, an estimated 100,000 snow geese died from avian cholera in the RBA. To date, waterbird loss from disease in the RBA has been diminished because many Central Flyway waterfowl in dry and cold springs move to the Platte River Valley, where few disease problems have existed. Thus, changes that diminish wetland habitat on the Platte to waterfowl pose the specter of increased crowding and higher losses of waterfowl and other waterbirds from disease in the RBA.

Working Toward a Solution

Efforts to protect remaining meadows and to maintain wide channels have become a high priority for conservation organizations and government agencies attempting to preserve the Platte as a key staging area for sandhill crane and the endangered whooping crane. A section of the Platte River Valley 3 miles wide (about 5 km) and 56 miles long (90 km), from Lexington to Denman, was designated as critical habitat for the whooping crane under the Endangered Species Act of 1973. About 13,000 acres of the Platte River Valley have been acquired in fee title or perpetual easement for migratory waterbird use in tracts located from near Overton to south of Grand Island. Most of these lands have been purchased by the Platte River Trust, the Nature Conservancy, and the National Audubon Society. Conservation lands are being actively managed to meet the needs of sandhill and whooping cranes and other migratory waterbirds, including the least tern (classified as "endangered" in the Great Plains) and the piping plover (classified as "threatened"). Terns and plovers nest on sandbars in the Platte River.

To adequately protect the channels for roosting and wet meadows for foraging, instream flows must be sufficient to maintain wide, shallow river channels and, in surrounding meadows, high water tables. High-energy cereal grains are also crucial, but if roosting habitat and meadow habitat remain widely distributed, much more cropland is more accessible to cranes for obtaining corn to meet their energy and fat storage needs.

Securing adequate flows to meet needs of migratory waterbirds has been a difficult task because of intense competition for the Platte's waters. Historically, water in rivers of the Great Plains has been appropriated mostly for consumptive uses, particularly for irrigation and hydropower development. In line with the doctrine of appropriation, water rights have been allocated based on chronological order of application and, so long as water laws are followed, the water right is maintained indefinetly. At the Platte, about 70% of average annual flows were allocated before the need for adequate instream flows to maintain the riverine ecosystem was widely recognized.

The growing body of information about the habitat needs of sandhill cranes, whooping cranes, and other waterbirds using the Platte River Valley has helped ensure that allocation of flows for consumptive uses upstream have been appropriately mitigated in the past two decades. However, habitat losses from water projects completed before the maintenance of instream flows for wildlife became a consideration must also be addressed: a major part of habitat loss is from projects completed decades ago.

A big step toward ensuring that adequate habitat will be maintained for migratory waterbirds in the future was taken in July 1997 when a cooperative agreement was signed by the governors of Nebraska, Colorado, and Wyoming and by Interior Secretary Bruce Babbitt. The agreement lays out a comprehensive habitat restoration plan with a long-term goal of making available 130,000-150,000 additional acre-feet of water each year in the Platte during those periods when most needed to meet migratory bird requirements. Also, the plan calls for restoration and protection of 29,000 acres of habitat between Lexington and Chapman, Nebraska over the next 25 years. Habitat complexes are to contain those key elements that research has indicated are necessary to attract and meet the needs of whooping and sandhill cranes, including wide, unobstructed channels and large tracts of wet meadow and grassland. Once restored, each habitat complex would have the potential for attracting thousands of sandhill cranes, thereby reducing pressure on existing areas that are still inhabitable.

Although the July 1997 cooperative agreement is nonbinding, its failure would cause conflicts to resume that have led to decades of litigation and stalemate over how the waters of the Platte River Basin should be managed. Thus, while habitat conditions for numerous species of migratory waterbirds remain precarious in the Central Platte Valley at the approach of a new century, there is renewed optimism. Progress, although slowed by a myriad of water-related issues, is continuing because of the strong commitment of many in the conservation community, government, and public to maintain this world-class gathering of birds. Driving this effort is a recognition that if the crane chorus falls silent along the Platte, one of nature's most enduring and spectacular rituals of spring will have been lost -- and on our watch.

Beyond the immediate problems and potential solutions for sandhill cranes along the Platte, the long-term well-being of the midcontinent population of sandhill cranes will require a comprehensive understanding of the needs of cranes throughout the annual cycle. At the present time, we lack a thorough understanding of the habitat needs of specific subpopulations or even subspecies. We do not know the breeding grounds of subspecies staging along various sections of the Platte, their migration routes, where they spend winter, or even how long they stay and draw resources from the Platte.

In March 1998, I had my technician, Dave Brandt, attach satellite-linked transmitters to 1 greater, 2 Canadian, and 2 lesser adult sandhill cranes in the Platte River Valley as the first step toward gaining a better understanding of where cranes of the 3 subspecies spend the rest of the year. Preliminary results from this study, which is scheduled to continue through the year 2001, are encouraging. Locations of the satellite-monitored cranes are relayed back to my laboratory every 4 to 7 days, providing types of information previously not available. As a result of this new technology, it will be possible to follow cranes throughout the annual cycle, pinpoint those areas which are most important to the birds, and put crane managers in a better position to focus attention where most needed.

Maintaining healthy populations of sandhill cranes and other migratory waterbirds in the face of continuing change in the American landscape is not easy: it will require the continued strong support of the public, particularly those who derive special enjoyment from watching birds. In the meantime, if you have not traveled to the Platte in late March and seen the cranes, I encourage you to do so. There is no similar gathering of cranes on this planet or beyond -- except perchance in some far valley of the Milky Way.

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