Aransas National Wildlife Refuge: The Whooping Crane's Vulnerable Winter Retreat

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Whooping cranes at Aransas National Wildlife Refuge. (Paul A. Johnsgard)

By Paul A. Johnsgard

Perhaps no North American species of bird has come closer to extinction and yet managed to survive into the twenty-first century than has the whooping crane. The ratification and activation of the Migratory Bird Treaty in 1918 had brought the whooping cranes of Canada and the US into complete protection, but by then there were probably no more than about of these sixty birds still surviving. And, at least twenty-five more were killed during the next four years. By then it was apparent that most of the surviving birds were wintering in coastal Texas and migrating north to unknown breeding grounds somewhere in Canada. It was not until 1955 that the species’ breeding grounds were in an already protected area on the border of Alberta and Northwest Territory, Wood Buffalo National Park.

In Texas, a second tiny group of whooping cranes that had wintered on the vast King Ranch of southern Texas disappeared by 1937, leaving the last known wintering population of about a few dozen birds on the Blackjack Peninsula of coastal Texas north of Corpus Christi, between San Antonio and Aransas bays. A small residential flock also then still survived in the prairies and coastal marshes of Louisiana, where a dozen or so birds had been found around White Lake during the construction of the Intracoastal Waterway in 1929.

Ironically, Myron Swenk, Nebraska’s premier (and only) ornithologist of the 1930s, was responsible for the sadly mistaken belief that there were still perhaps three hundred whooping cranes still in existence during the 1930s. This assumption was based on unverified reports by volunteer birds watchers tallying spring migrants. These reports were subsequently published in the state’s ornithological journal, The Nebraska Bird Review, and were accepted without question by the professional ornithologists of the American Ornithologists’ Union, which thus failed to understand the gravity of the species’ actual precarious status.

In another turn of irony, the Great Depression of the 1930s had the beneficial effect of stimulating the federal government to employ thousands of out-of-work people in the Civilian Conservation Corps. This workforce undertook innumerable conservation-oriented activities, such as constructing more than eight hundred parks nationwide, planting millions of trees, and developing roads and facilities for sites that were or were to become national parks and national wildlife refuges.

Whooping cranes at Aransas National Wildlife Refuge. (Paul A. Johnsgard)

One of the many locations studied by the Department of Interior and recommended for inclusion in the rapidly expanding system of national wildlife refuges during the 1930s was the Blackjack Peninsula. This area was the only known winter home of the entire remnant migratory whooping crane flock, and known for wintering a great variety of shorebirds and waterfowl. It also supported a resident population of the already rare Attwater’s prairie chicken, a race of the greater prairie-chicken endemic to the coastal prairies of Texas that by the 1937 had already lost 93 percent of its original habitat and whose population had been reduced from nearly a million birds to less than nine thousand.

In December of 1937, President Franklin D. Roosevelt signed an executive order creating the Aransas Migratory Waterfowl Refuge (later renamed the Aransas National Wildlife Refuge), purchasing land that encompassed much of Blackjack Peninsula, totaling over forty-seven thousand acres. The area’s bargain-basement purchase (at about ten dollars per acre) unfortunately excluded control of grazing rights and mineral rights, both of which would later cause serious problems in refuge management. Additionally, shooting rights by a hunting club extended to the refuge’s boundaries, threatening the safety of any cranes straying beyond the refuge. To make matters worse, in 1940 the Army Corps of Engineers began to dredge a channel for the expanding Gulf Intracoastal Waterway, cutting a three-hundred-foot wide ditch and associated right-of-way through a previously isolated part of the refuge.

During the area’s initial fall and winter of 1938–39, the refuge manager counted fourteen whooping cranes, including two juveniles, causing him to estimate that a total of no more than eighteen birds might be present, assuming that as many as two birds might have been overlooked. In the following fall five pairs returned with young, two of the pairs tending twins, and five other adults were also present, for a total of twenty-two birds.

In 1940 oil drilling began just outside the refuge’s limits, and the Army Air Corps took over nearby Matagorda Island for military use. Along with nearby San José Island, this fifty-six-thousand-acre barrier island was an important foraging area for the cranes and had been recommended for inclusion in the refuge, but the federal budget hadn’t permitted its purchase.

Whooping cranes at Aransas National Wildlife Refuge. (Paul A. Johnsgard)

During the fall of 1941, only fourteen adult whooping cranes and two young returned to Aransas, a total that marks an historic population low point for the species, although six additional birds were then still surviving in Louisiana. The Louisiana flock was extirpated by 1950–51, as a probable result of coastal storms. By that time the Wood Buffalo–Aransas flock had increased by twenty birds, reaching a grand total of thirty-four, but this total represented an average population gain of only two birds annually.

By the end of the next decade (1959–60), the Wood Buffalo–Aransas flock still hovered precariously at only thirty-three birds, but by the fall of 1969–70 it had gained another twenty-three birds, totaling fifty-six. By 1979–80 the total was seventy-six, and by 1989–90 the flock had experienced a burst of breeding success and had reached 146. At the turn of the twenty-first century the autumn refuge total was 188 birds, and by 2008 the flock had reached an amazing record total of 283 cranes.

During the past century the Aransas refuge has had more than its share of disappointments. Oil drilling, illegal shooting, and other disturbances along the Intracoastal Waterway became serious problems during the 1940s, and still persist. During World War II, the fifty-six-thousand-acre Matagorda Island was used as a practice bombing range by the Air Force, causing an unknown amount of disturbance and damage to the cranes. It was not until 1955, a year after the crane’s nesting grounds in Wood Buffalo Park were finally discovered, that the Air Force agreed not to undertake nighttime bombing practice on Matagorda Island, which would have caused a major wildlife disturbance. In 1973 the Aransas National Wildlife Refuge finally acquired management jurisdiction over much of Matagorda Island. In 1995 the entire island was named Matagorda Island Wildlife Management Area, to be managed jointly by the state and federal government for conserving rare and endangered birds and supporting migratory bird management.

Other chronic problems have long existed at Aransas. By 1970 heavy grazing by 2,500–4,000 cattle on the refuge had impacted grassland-dependent birds such as the Attwater’s prairie-chicken, and it eventually was extirpated from the area. Since then, grazing has been terminated and the prairie conditions have improved, although invasive growth by shinnery oak is a significant problem. Periodic hurricanes have also ravaged the area. In August of 1965 a major hurricane passing up the Texas coast slammed into Matagorda Island, illuminating the region’s vulnerability to such storms. Luckily these increasingly frequent late-summer storms have so far occurred before the cranes are present on the refuge. Another impending ecological problem in the invasion of black mangroves into the region, which is likely to impact foraging opportunities for whooping cranes and other marshland foraging birds.

Disaster struck the Wood Buffalo-Aransas flock in the fall of 2008 with the onset of a prolonged drought in Texas. The major source of fresh water to Aransas National Wildlife Refuge is the Guadalupe River, which maintains the salinity of the coastal wetlands and allows for the survival of blue crabs, the whooping crane’s major winter food. Increased drought-related diversions of this river water by Texas water authorities (the Texas Commission on Environmental Quality) resulted in an increased salinity of water around the Aransas refuge. These salinity changes decimated the local population of blue crabs and led to the death of at least twenty-three whooping cranes during the winter of 2008–09, reducing the crane population to 263 by the spring of 2009. A lawsuit filed in US District Court in 2010 resulted in a finding three years later to the effect that such diversions violated the Endangered Species Act and initiated the development of a Habitat Conservation Plan for Whooping Cranes. This plan should reduce the likelihood of a repeat of the 2008–09 disaster, although the court’s decision is still under appeal.

Whooping cranes at Aransas National Wildlife Refuge. (Paul A. Johnsgard)

During 2011, the Wood Buffalo–Aransas flock built a record high of seventy-five nests and fledged about thirty-seven young. In spite of that impressive nesting success, the winter 2011–12 population census at Aransas resulted in a total of only 254 birds within the primary survey area, although others were known to winter outside the survey’s geographic limits. The Fish and Wildlife Service acknowledged that, because of sampling constraints associated with a less comprehensive winter survey protocol, the flock’s size then could statistically have been anywhere from 199 to 325 birds. Such confidence limits are far greater than any historical annual population increase or decrease of the Wood Buffalo–Aransas flock, making it impossible to estimate the population trajectory of this vitally important population.

In 2012 a total of thirty-one families were counted at Wood Buffalo Park, including two sets of twins, for a total of thirty-three chicks. No specific numbers have been released from the winter 2012–13 surveys of adults and juveniles at Aransas, other than the comment that it was generally believed that there probably were more than 250 birds in the wild flock. During the summer of 2013, twenty-eight whooping crane chicks (no twins) resulting from seventy-four nests were counted during a July survey. The 2013–14 Aransas population was estimated at a record 303 birds.

Since the establishment of Aransas National Wildlife Refuge, many other major conservation efforts have been undertaken toward preserving and restoring whooping cranes and to produce a second flock independent of the Wood Buffalo–Aransas population. These have included an unsuccessful effort to hatch and raise whooping cranes using wild sandhill cranes as foster parents in Idaho, and a similarly unsuccessful effort to establish a resident whooping crane flock in the Kissimmee Prairie of Florida. In 2011 ten hand-reared whooping cranes were introduced into the White Lake region of southwestern Louisiana, the start of a multiyear effort to reestablish a resident flock in that state. By the beginning of 2014 that flock had been increased to about thirty-five birds, but in February vandals shot and killed the female of a subadult pair that were building a “practice nest” and seriously wounded the male, which later died.

The most innovative attempt is an audacious experiment (“Operation Migration”) involving the rearing of whooping cranes in Wisconsin and training them (with the guidance of ultralight aircraft) to migrate to Florida, in a heroic effort to establish a independent migratory flock in eastern North America. The success of that effort will ultimately depend on the abilities of these birds to successfully breed and rear young under wild conditions, including often lethal threats to the young from blood-draining bites by black flies. So far, the results of these efforts are still uncertain but promising (Duff, 2014).

Given the recent warming and drying climate trend in the Great Plains, and consequent increased losses of wetlands, the future of the Wood Buffalo Park–Aransas flock of whooping cranes is still by no means secure. However, without the establishment of Aransas National Wildlife Refuge at a critical time, the species would almost certainly have added the passenger pigeon, Carolina parakeet, and Eskimo curlew to the dismal list of twentieth-century North American bird extinctions.

 

References

Duff, J. “Reintroducing an Endangered Species Is Complicated.” Prairie Fire, February 2014: 9–12.

Hughes, J. M. Cranes: A Natural History of a Bird in Crisis. Buffalo, NY: Firefly Books, 2008.

Johnsgard, P. A. Crane Music: A Natural History of American Cranes. Smithsonian Institution Press, Washington, DC, 1991.

Johnsgard, P. A. The Sandhill and Whooping Cranes: Ancient Voices over the America’s Wetlands. Lincoln, NE: University of Nebraska Press, 2011.

Johnsgard, P. A., and K. Gil-Weir. “The Whooping Cranes: Survivors against All Odds.” Prairie Fire, September 2010: 12, 13, 16, 22.

 

Photo Credits: All photos of Whooping cranes at Aranas National Refuge by Paul A. Johnsgard

Immigration in Nebraska