Nebraska's Magical Sandhill Crane Migration

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Sandhill cranes against the moon, 2011. (Paul A. Johnsgard)

By Paul A. Johnsgard

Over the past 50 years I have often been asked why, of all the places I have lived and visited, I chose Nebraska as the place I have decided to spend the rest of my life. I quite willingly admit that Nebraska lacks the mountain grandeur of Colorado, the wonderful rocky coastline of Oregon and the stunning glaciers of Alaska. Yet I quickly point out that we Nebraskans can claim the continent’s largest remaining native prairie flora and its associated prairie wildlife, perched on the largest region of picturesque sand dunes in the western hemisphere. This in turn rests atop one of the greatest reservoirs of fresh water in the world, whose artesian springs give birth to such beautiful Sandhills streams as the Calamus, Loup, Dismal and Elkhorn. Then, as a trump card, I say, “Oh yes, and for six weeks in spring we also have what is one of the largest and most spectacular concentrations of birds in the world.”

Compared with other spectacles I have seen, such as the great coastal seabird colonies such as Alaska’s Pribilof Islands, Nebraska’s cranes and migratory waterfowl can be seen without fighting foul weather and high winds. The equally famous spectacle of at least a million wildebeests migrating slowly across the Serengeti plains of Tanzania can be relatively boring, and is also somewhat smelly. By comparison, there is boundless joy in sitting quietly among prairie grasses along the Platte River, with an azure sky overhead and a chorus of crane music drifting down from a thousand feet above. As the silvery gray birds wheel gracefully about in a giant vortex of life and call excitedly to one another as they descend to their safe and ancestral resting places in the river, I too know I have witnessed my personal Elysium.

We have no idea as to how long this magnificent spectacle has gone on. Cranes have waded the wetlands of the world for at least 50 million years, a period more than 10 times longer than the time since ancestral humans first walked upright. They have probably migrated across what is now Nebraska for millions of years, or longer than the Platte River has been existence. It seems likely that, at the end of the Pleistocene epoch more than 10,000 year ago, as outwashes from the retreating glaciers of the northern plains were spilling into the Missouri River, and the glaciers of the western mountains were also melting, the Platte River or its antecedents had their origin, carving new water routes through the tundra-like landscapes of the central plains. We can also imagine that sandhill cranes and other arctic-adapted birds such as snow geese annually followed the warming landscape northward, breeding during the brief summers and retreating to ice-free wetlands each winter.

Sandhill cranes against the sun. (Paul A. Johnsgard)

No doubt early Native Americans saw and rejoiced in these flights; they must have represented a vital source of fresh meat after a winter of probable near-starvation. But the crane migration remained largely unknown until very recent times; early immigrants following the Platte west typically didn’t cross Nebraska Territory until late spring, so that they might cross the mountain passes of Wyoming during the snow-free period of summer.

The first estimates of the crane migration date from the early 1940s. A writer in the April 19, 1934 Hastings Daily Tribune hypothesized that the stretch of the Platte between Kearney and Odessa “is crossed twice a year by more sandhill cranes than any other strip of similar length in the same latitude anywhere from coast to coast.” In 1945 Dr. William Breckenridge, an ornithologist from the University of Minnesota, provided one of the first numerical estimates of spring crane numbers in the central Platte Valley. His counts suggest that in this period, before the advent of extensive use of fertilizers, pesticides and irrigation, the numbers of sandhill cranes seen near the confluence of the North Platte and South Platte rivers were in the general range of 30,000–40,000 birds. No contemporary estimates of birds farther downstream are available, but one might imagine a population of no more than 100,000 or so birds existed then.

By the early 1960s, with the legalization of sandhill crane hunting in Texas and New Mexico, the U.S. Fish and Wildlife Service began systematic surveys of spring sandhill crane numbers in the Plate Valley, where the mid-continent arctic-breeding lesser sandhills and many of the subarctic-breeding “Canadian” sandhill cranes concentrate in March. Early survey estimates were subject to great variations but generally ranged from about 150,000–200,000 cranes. By the mid-1970s, Fish and Wildlife Service data suggested a maximum Platte Valley population of 200,000–270,000 individuals. Since then the population estimates for the Platte Valley have gradually crept upward, so that now 450,000–500,000 represents the generally accepted estimate. This estimate has remained fairly stable recently, and has been generally supported by independent ground surveys and other methods of aerial survey.

Sandhills in flight. (Paul A. Johnsgard)

It is difficult to know what factors might have prompted the remarkable growth of the mid-continent population of sandhill cranes during the past 70 years, but the massive increase in corn production in the Platte Valley since the 1940s and the attendant availability of unharvested corn left in the fields each fall has certainly been important. This corn bonanza has provided a nearly unlimited source of food for cranes as they move north in the spring, when they need a maximum fat storage to prepare them for the rigors of their remaining migration and the stresses associated with an arctic nesting environment. Quite possibly the amelioration of the climate in arctic regions has also had an important effect, by lengthening the frost-free period to a point that the nearly 100 days required for nest-building, egg-laying, incubation and chick-rearing can now often be comfortably fit between the last spring blizzard and the first fall snows.

Even with a successful breeding season a pair of sandhill canes only infrequently manages to produce and raise two chicks from their two-egg clutch to fledging. Besides other losses, one of the eggs (that laid first) always hatches a day or two before the other, and the first-hatched chick usually fights with and sometimes kills its younger sibling, Should both young fledge, however, the family soon forms a strong social bond, which is held together by mutual calling and postural displays. A juvenile crane is likely to remain closely attached to its parents for up to about three years, when sexual maturity leads to independence. Many of the sandhill cranes breeding in the mild climate of Florida may attempt to bred when only two years (in males) to three years (in females) of age. However, it is believed that arctic-breeding cranes undergoing the stresses of long migrations and extreme climatic conditions may require four to five years to achieve breeding status.

How long social attachments persist among parents, siblings and other close relatives is still uncertain in wild cranes. It is generally true that all species of cranes form permanent pair bonds, but these are often broken by the death of one of the partners or, less often, by divorce. Divorce is rare among sandhill pairs that have a history of successful reproduction, and the ability of the male to establish and maintain a desirable nesting territory seems to be a major factor in determining if a pair bond will be maintained between seasons.

Family bonds among whooping cranes may be stronger than those in sandhills. Long-term observations of color-banded birds has shown that the small flock sizes typical of whooping cranes result from the long-term social attachments of closely related individuals, so that as many as four generations of birds can be present in a single migrating assemblage. This factor, along with the great potential longevity of cranes, often exceeding 30 years in unhunted populations, allows for real cultural transformation of information from generation to generation. The older birds may actively or passively pass on important information about migration routes and migratory staging areas, as well as suitable and secure breeding and wintering sites.

Through such intergenerational learning, it is likely that an adult arctic-breeding sandhill crane knows more about the intimate geography of North America than does a professional airline pilot. Furthermore, each arctic-breeding crane must undertake these hazardous migrations of 3,000 miles or more twice yearly. These migrations are performed in the face of legal “sport” hunting in nearly every Canadian province and every American state on its migration route between Alaska or Canada and Texas. Nebraska is the only Central Flyways state that has never attempted to obtain permission from federal authorities for initiating a sandhill crane hunting season. We Nebraskans can be proud of this fact; some other states where sandhill cranes have traditionally been protected are now clamoring for an open season. The most recent state to establish a highly controversial open season is Kentucky.

Sandhill crane hunting has greatly increased in popularity since its initiation in Texas and New Mexico in the early 1960s; now roughly 30,000 cranes in the mid-continent population are killed each year, namely about 6 percent of the total, or most of each year’s total production of juveniles. This annual hunting mortality rate means that a crane living in the Central Flyway is in about 50 percent greater danger of being killed during any single year at the hands of a sport hunter than was a U.S. soldier serving over the entire 10-year period in the Iraq war.

For those sandhill cranes that survived the long hunting season and winter months in the playa wetlands and marshes of Texas, New Mexico, Arizona and Mexico, their safe return to the Platte River and its surrounding corn-rich valley can only be a vast relief. We humans too can also briefly forget our worries of daily life by visiting the Platte Valley in early spring and getting a glimpse of wild America. One need not be a bird expert to enjoy this almost incredible visual and auditory experience, which I can promise will indelibly remain with you for a lifetime.

Visitors to the central Platte Valley may choose to experience a sunrise or sunset roosting flight in a commercial blind, such as at the Rowe Audubon Sanctuary near Gibbon or one operated by the Nebraska Nature and Visitor Center at the I-80 Alda interchange. Or, simply watch the amazing passing parade of cranes, geese and other birds from one of the two public viewing platforms, which are located at the Platte River bridges along the highways directly south of Alda and Gibbon. In any case, don’t pass up a sunrise or sunset experience in favor of a quick trip; to do so is to cheat yourself out of a brief glimpse of nirvana.

 

Image Credits: Paul A. Johnsgard

 

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