The Whooping Cranes: Survivors Against All Odds

By Karine Gil-Weir and Paul A. Johnsgard

Although many Nebraskans have had the indescribable pleasure and joy of watching tens of thousands of sandhill cranes overhead, or even seeing them roosting on Platte River bars and islands during spring migration, only a tiny handful can say that they have ever seen whooping cranes in Nebraska. The sheer odds against it are daunting. Compared with 450,000–500,000 sandhill cranes migrating through the state each March, there are now less than 300 whooping cranes in the flock that annually migrates from Aransas National Wildlife Refuge, on Texas’s Gulf Coast, to Wood Buffalo National Park, straddling the border of Alberta and Canada’s Northwest Territories. Added to this numerical population disparity, whooping cranes migrate somewhat later in spring than the sandhills (during April in Nebraska), after most crane watchers have gone home. During daytime foraging, they also usually frequent rather remote wetlands far from any roads and generally move in small groups consisting of pairs, a family or extended families that often consist of a pair and one or more generations of their offspring.

Collectively, the two of us have spent nearly 50 years studying and thinking about cranes; Dr. Johnsgard has assiduously watched cranes in Nebraska annually since 1961, while Dr. Gil has been doing full-time research on cranes at Texas A & M and Nebraska’s Crane Trust since 2002. This devotion to birds might be considered as obsessive-compulsive behavior by many, but the sights and sounds of wild cranes are as intoxicating to us as the odors of tropical wildflowers. To be able to experience them only once would be as painful as being condemned to observe only a single sunset during one’s lifetime.

The lifelong attraction of cranes to many people has meant that we now know as much about the lives of sandhill and whooping cranes as almost any other North American bird. Because the whooping crane was listed as a nationally endangered species in 1972, federal funding was created for research and developing a survival strategy. In 1941, only 22 whooping cranes existed (16 in Texas and six in coastal Louisiana) in the wild. The Louisiana population was extirpated in 1949. It was not until 1954 that their Canadian breeding grounds were discovered and not until 1986 that their world population reached 100 individuals. It is an ironic fact that, because of the whooping crane’s perilous population status, the Platte River has been protected from destruction by powerful irrigation interests through the identification of the central Platte Valley as critical habitat for the species. Thereby, the whooping crane’s threat of extinction has helped preserve Platte habitats for many other water-dependent species (including three other threatened or endangered birds and fish) and set the stage for the enactment of the 2006 Platte River Recovery Plan. This plan is a $317 million cooperative program for Platte River wetland preservation and restoration involving Colorado, Wyoming and Nebraska. The recognition of the Platte’s importance to the survival of the whooping crane also resulted in the establishment of a habitat mitigation fund associated with the building of the Grayrocks Dam on a major Platte tributary (the Laramie River) in eastern Wyoming, and the formation in 1978 of the Platte River Whooping Crane Habitat Maintenance Trust (recently renamed the Crane Trust).

The central Platte Valley was the first of the areas federally designated as critical habitat for migratory whooping cranes between Texas and the Canadian border. Other Great Plains sites that have been similarly identified as critical habitats include Oklahoma’s Salt Plains National Wildlife Refuge and Cheyenne Bottoms State Wildlife Area and Quivira National Wildlife Refuge, both in Kansas.

Among more than 500 spring-fall observations of whooping cranes obtained between 1943 and 1999 and analyzed by Professor Amy Richert and Dr. Jane Austin, the largest number (69 and 33 percent) were from Nebraska, proving the critical importance of the Platte and other Nebraska rivers to migrating whooping cranes. There were fewer migratory sightings in North Dakota, Kansas, South Dakota, Montana, Oklahoma, Montana and Texas. Dr. Gil’s new statistics showed the same trend during spring 2007 and 2010, with the highest number of reports along the Central Flyway received from Nebraska. During the last 30 years, sightings of whooping cranes in the state of Nebraska and at the Platte River have been documented, and since 2007, with the reactivated Whooper Watch program, reports have been increasing throughout the state.

The accompanying chart shows the numbers of whooping cranes documented by the Crane Trust in Nebraska and the Platte River during spring and fall from 1989 to 2009. In Nebraska, most historic sightings of migrating whooping cranes have occurred along the central Platte River but also have included the Niobrara, Middle Loup and North Loup rivers. These include Buffalo, Cherry, Custer, Hall, Kearney, Keya Paha, Rock, Lincoln, Loup, Phelps, Sherman, Valley, Howard, Holt, Harlan, Hamilton, Adams, Garfield, Dawson and Blaine counties, among others with a lower number of reports. A comparison of the number of counties used along Nebraska as stopovers between spring migration 2006 (seven counties), 2007 (nine counties), 2008 (seven counties) and 2010 (nine counties) shows that counties selected may change annually due environmental conditions and other factors to be studied. This spring the highest numbers of confirmed sightings were reported in Custer (19), Kearney (eight) and Buffalo (eight). Richert and Austin found that most locations where cranes have been observed were more than a half-mile from any human structures or developments. Most were more than a third of a mile from the nearest power or phone lines, and about half of all the roost sites and two-thirds of the foraging sites had unobstructed visibility for more than a quarter-mile and were associated with river widths greater than 700 feet. Clearly, visibility and freedom from proximity to human activity are important aspects of whooping crane requirements. They also need access to wetlands for both foraging and nocturnal roosting: like sandhills, they prefer to roost in shallow water, well away from heavy shoreline or island vegetation.

Jane Austin and Amy Richert reported that the most frequent date for spring migration sightings was April 6 in Oklahoma, April 12 in Kansas and Nebraska, April 19 in South and North Dakota and April 26 in Montana. In Nebraska, records summarized by Johnsgard similarly indicated that the peak spring migration period is April 1–15, and the peak of fall migration is from October 11–24. Starting in 1979, from reports analyzed by Gil, some whooping cranes have been arriving in Nebraska much earlier than was previously was the case, probably because they have become socially attached to sandhill flocks that now typically arrive in mid-February. This year the first whooping crane arrived with sandhill cranes in March 5 and stayed until April 3, and this was reported by one of the Whooper Watch volunteers after a training session with Dr. Gil.

Partly in order to better document the role of individual cranes in migration and their population structure, a program of color banding juveniles was undertaken in 1977 (when there were only 62 adults and 13 juveniles at Wood Buffalo National Park) and was continued until 1988. Dr. Gil has analyzed the survival and individual reproductive success from these banding efforts. Based on subsequent observations on the breeding grounds, on migration and at Aransas, she determined that of the 132 banded birds, 24 were still surviving by 2009. During 2010, only 16 of the banded birds were confirmed as still surviving. In fact, few of the banded birds were still alive, based on alternative identifications at the same wintering and breeding grounds for consecutive years. All survivors were at least 22 years old, and one had reached 32 years of age (Lobstick). From the group of 16 chicks banded in 1985, at least five of them were confirmed to be 25 years old. Also, there are potentially nine individuals 23 years old! Many cranes are known to have survived more than 30 years in captivity, and some wild sandhills are also known to have had similar life spans.

Although first-year survival of banded birds average 42 percent in Gil’s analysis, survivorship of subadults increases annually until four years of age. Older age classes of whooping cranes have the highest mean survival rates and breeding success, reaching a maximum fecundity from seven to 14 years of age and declining after slowly. Indeed, one female at Wood Buffalo Park was still nesting at 27 years of age.

Because they are federally protected, various accidents are probably the major cause of adult mortality, especially collisions with overhead utility lines by migrating birds. By comparison, sport hunting is the cause of most mortality in sandhill cranes, resulting in the deaths of more than 5 percent of the lesser sandhill crane population annually. Thankfully, hunting for sandhill cranes in Nebraska has never been allowed because of the special importance of the Platte to whooping cranes.

Partly because of their great longevity, and their strong family bonds, it is of interest to track individual and population characteristics among color-banded birds. Dr. Gil has determined such times of initial breeding, breeding success, length of pair bonds, remating after loss of a mate and many interesting intergenerational associations. These include such information as the distances between the nests and wintering territories of parents and offspring and the common use of migratory stopover areas by close relatives, through four generations. Of special interest is the genetic legacy of a single identified pair that produced four descendents, and from three of them that were banded, it was possible to estimate that at least 43 direct descendents contributed to the wintering Aransas population from 1977 to 2007. During that period, the pair produced at least 18 second-generation offspring that survived long enough to reach the Texas wintering grounds. The same genetic line subsequently produced 17 third-generation birds and four fourth-generation offspring that likewise were able to survive the 2,000-mile flight to Texas. Remarkably, many of these birds have continued to use the very same migratory stopover points as did their great-grandparents, showing the power of place memory in crane migration and the probable importance of migratory traditions in long-lived and long-distance migrants such as cranes.

The Aransas-Wood Buffalo flock has recently undergone some hard times, especially during the winter of 2008–2009, when a severe drought in Texas resulted in the loss of 23 of its early-winter population of 270 birds. A year later, the total 2009–2010 winter population at Aransas was about 263. This summer, in May, at Wood Buffalo National Park were found 74 nests on aerial surveys, and from at least 20 chicks localized in August 2010, nine of them were banded and tagged with satellite and VHF radio-telemetry transmitters by The Crane Trust-Nebraska, USGS-North Dakota, Canadian Wildlife Service, International Crane Foundation and other collaborators. This effort totalizes 11 radio banded whooping cranes, because two of them were banded for the first time in the wintering ground in Texas, during December 2009, with collaboration of the USFW-Texas and others. It had been 22 years since banding was last done on the breeding grounds, and this current banding will result in new sources of valuable population data for the understanding and conservation of this endangered species throughout its migratory corridor.

For the biologists who have worked so hard to restore whooping cranes, even small miracles such as the gaining of a few chicks per year must be rewarding. At times like these, with oil polluting our precious Gulf Coast and the sight of majestic seabirds such as brown pelicans dripping with oil, the thought of immaculate whooping cranes flying high overhead is a comforting thought, and one that confirms that we must all act in such a way as to keep natural treasures such as cranes a reality.

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