No one knows more about whooping cranes than Tom Stehn, who studied and cared for them for three decades. Then he retired—only to discover that the magnificent and endangered birds needed him more than ever.
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Early last December, Tom Stehn was enjoying his retirement in Aransas Pass, soaking in his hot tub after a morning of windsurfing, when the phone rang. He grimaced for a moment but hopped out of the water naked to see who was bothering him. A U.S. marshal was calling from his car, which was parked in Stehn’s driveway. A federal judge in Corpus Christi wanted him to testify about the deaths of 23 whooping cranes he’d reported during the winter of 2008 to 2009, two years before he had retired. The marshal asked if Stehn could come to court immediately. “All right,” he said, “but give me a minute to put on my clothes.”
Stehn knew what the case was about. A longtime biologist for the U.S. Fish and Wildlife Service, he had served as its whooping crane coordinator for over a decade. No one had more hands-on experience with the birds, which are among the most endangered in North America. He had flown on countless aerial surveys to identify the whooping cranes’ winter territories in the Aransas National Wildlife Refuge, studied their habitat, measured the salinity of their marshes, celebrated their return each year, nurtured their sick, and, when he could, recovered their dead. In the winter of 2008 an emaciated juvenile had died in his arms.
Over the years, Stehn had watched the flock grow from 71 to nearly 300 birds. But he determined that during the drought of 2008 and 2009, 8.5 percent of the wintering flock and nearly 45 percent of the first-year juveniles had died. The following year, coastal tourism businesses, environmentalists, and the O’Connor family of Victoria, who owns tens of thousands of acres near the Guadalupe River, formed a nonprofit group called the Aransas Project and sued the state. The organization claimed that, under the Endangered Species Act, the Texas Commission on Environmental Quality (TCEQ) was responsible for the deaths of the cranes because it had failed to allow enough freshwater to flow from the Guadalupe River into San Antonio Bay, which adjoins the wildlife refuge.
The State of Texas, led by the Guadalupe–Blanco River Authority (GBRA), countered that the lawsuit was based on pure speculation. Of the 23 birds that Stehn had reported dead, only 4 carcasses had been recovered. How could he prove the others had died? And even if they had, how could the environmentalists know that the deaths resulted from a lack of freshwater? Witnesses for the state contended that computer models proved the whooping cranes could survive perfectly well with very little freshwater. They even claimed that because of a special gland, whooping cranes might not need to drink freshwater at all.
The case has exposed a long-simmering battle between the two sides. Although state law directs the TCEQ to plan for freshwater inflows to keep Texas bays healthy and productive, environmentalists have been complaining for years that the agency has failed to live up to its responsibilities. In 2003, for example, a group of environmentalists had applied for water rights to protect wildlife in San Antonio Bay, and the TCEQ denied the request. The GBRA, in particular, has a great deal at stake. Its priorities are cities, farmers, and industry, and there are plans for several new power plants, including a proposed nuclear facility, to be built in the region. If the plaintiffs win, those projects could be put on hold.
Both parties had visited Stehn’s old office and obtained copies of his annual reports, and both had tried to recruit him as a paid expert witness. Though the Department of the Interior typically prohibits its biologists from testifying as expert witnesses, Stehn was inclined to stay out of the trial anyway. He had been concerned about the management of the Guadalupe River for years, and he worried that the state’s lawyers would try to destroy his life’s work to win the suit. U.S. district judge Janis Jack decided that Stehn’s testimony was essential, however, and she ordered each side to pay half of his $200-an-hour fee. “That’s good Christmas money,” the judge told him.
Since this was a bench trial, the case hinged primarily on whether Jack believed Stehn’s testimony. It was as if he were the only eyewitness at a murder trial and the victims were his children. Still, his presence did provide a bit of levity. Because his last name rhymes with the birds’ name, the judge would laugh when lawyers on both sides addressed him, in slips of the tongue, as “Mr. Crane.”
“I know these cranes,” he told the court. “I’ve been watching some of the same ones since 1982. I hate to be—what’s the word?—anthropomorphic, but it’s almost like they’re my kids out there.”
Of the fifteen species of cranes in the world, Stehn explained, only the whooping crane is territorial about its winter grounds. Mated pairs, some with juveniles they have reared during the summer in Canada, stake out an average of 425 acres of coastal marsh along the peninsulas and barrier islands of San Antonio Bay. When these territories were first mapped, in the late forties, there were only fourteen. As the flock grew over the years, the birds claimed smaller pieces of marsh, and by the winter of 2008 to 2009, Stehn had identified seventy different territories. Because the birds always returned to the same place, Stehn believed his weekly aerial surveys would allow him to count every crane. (The Lobstick territory had been used by the same male crane for thirty years.) He finally concluded that the flock had grown to 270 birds, plus or minus 2 or 3 percent.
After Stehn explained his census methods, Jim Blackburn, a veteran environmental attorney from Houston who was leading the case for the Aransas Project, asked the kind of question that lawyers hate: one whose answer they’re not absolutely sure of. He needed to know how many cranes had died that winter. “Is twenty-three your number?” he asked.
Stehn took a long moment to think about his response. Blackburn felt his gut turning over, because this was the heart of the case. Stehn noticed a look of puzzlement, almost panic, in Blackburn’s face and then said, “If I had to pick a number, it would be higher than twenty-three.”
The dead included mated pairs that had not had offspring as well as pure-white parents with rusty juveniles. But Stehn had also been watching ninety subadults, who tended to move about the refuge. “They can be on the refuge one day, they can fly across the bay to San José [Island] the next day or the next hour . . . they can be singles,” Stehn testified. “So you can’t ever tell if a bird like that is missing. It’s very reasonable to assume that some of them died that are not in that twenty-three.”
As for the 23 Stehn was certain had died, he could identify each by territory and date. Because the deaths had occurred all across the refuge, he believed that drought was the culprit. “It was a high-mortality winter,” Stehn said, “and at that point, the food supply was not good. There were low numbers of crabs, and the wolfberry crop had not been good. And from my experience, that kind of screams out that trouble is brewing.”
The refuge staff started feeding the cranes shelled corn at thirteen stations on upland parts of the cranes’ winter grounds, but this created a different problem. The birds are safest from predators in the open marsh, but when they fly inland, they increase their chances of being attacked by bobcats and other predators. To follow up on Stehn’s testimony, the environmentalists needed to prove that the lack of freshwater inflows was also related to the deaths. Two Rice University professors presented data that linked low river inflows to high crane mortality.
The GBRA fought back with a $2.14 million study it had helped fund in 2002 called the San Antonio Guadalupe Estuarine System, or SAGES, to determine the effect of freshwater inflows on whooping cranes. The report, which was released in 2009, around the same time that Stehn had reported the deaths of the cranes, concluded, “None of the study results indicated that habitat conditions [at the refuge] are marginal for crane survival and well-being.” The SAGES scientists built a conceptual computer model that indicated there was plenty of food, regardless of conditions.
During the testimony, Jack freely interrupted lawyers and questioned witnesses. She wrote notes furiously and researched suspect statements. At the outset of the trial she cracked, “I just wanted to rule out the fact that those [missing cranes] could have gone to New Mexico or, you know, to Antigua for the holidays or something.” Most of her remarks were aimed at the defense. She often shut down lines of questioning that seemed tiresome with a terse phrase: “Got it.” During eight days of testimony, the state heard that a lot.
A defense witness who reviewed the necropsy of one of the four crane carcasses noted that the bird had a greenish discoloration of the leg, which he associated with gangrene. Jack was astounded. She was well aware that gangrene is typically associated with a blue or black discoloration, so she grilled him about other weaknesses in his testimony. “I’m sorry,” she told the courtroom. “I know I’m being difficult with him, but I have never heard a scientist say when he saw something green that he thought of gangrene. I can’t quite move beyond it.”
Jack was even harder on R. Douglas Slack, the Texas A&M professor who led the SAGES study. Slack’s researchers had concluded that insects, clams, snails, and acorns would provide enough nutrition for the cranes, basing their findings in part on eighty to ninety hours’ worth of sometimes fuzzy videos that recorded the feeding habits of the birds. Stehn had presented Texas Parks and Wildlife Department data that showed that the cranes’ favored food, blue crabs, declined during times of low river inflow.
Jack grew exasperated with the SAGES model and its failure to incorporate the diet and mortality data that Stehn had collected. Under her intense questioning, Slack conceded that the cranes probably did need freshwater inflows—even if the model said they didn’t.
“Okay,” Jack said. “I’m just telling you, you can’t create a model. You can’t create a multiplier based on no information, which is what you’ve done. You have done it on what you figure is a normal, walking-around bird without determining how much energy it takes to forage for this versus forage for that. All these different things are critical to the well-being of the whooping crane. Even I can figure that one out.”
Slack’s most embarrassing moment came when the judge pressed him about the cranes’ supraorbital salt gland, which the defense claimed made them immune to the high salinity that comes with drought.
“I’ll tell you,” Jack said, “when the report was filed, I said, ‘What is this, a natural desalinization plan?’ So I looked it up, and there wasn’t anybody that ever described any such thing on a whooping crane.”
At one point, Jack asked Slack, “Where did you get that?”
“I don’t know,” he replied.
“You just made it up?”
“Yeah, I just made it up.”
After eight days of testimony, Jack heard no final arguments but instead asked each side to file briefs. She has encouraged both sides to work toward a settlement while she reviews the testimony, but if they cannot reach an agreement, she could issue a verdict as early as this month. If Jack rules for the Aransas Project, she could order the state to negotiate a Habitat Conservation Plan, in which the state would apportion the cranes a share of freshwater from the Guadalupe River. Bill West, the general manager of the GBRA, said that such a ruling would overturn traditional Texas water rights that date back more than one hundred years and disrupt the economic growth of the middle coast of Texas. “There’s no question,” he said. “It’s a classic example of federal intervention into state water rights by use of the Endangered Species Act. The judge does not have the authority to interfere with state water rights.”
In the meantime, Stehn has returned to Aransas Pass and to windsurfing, soaking in his hot tub, and enjoying the peace and quiet. But he laments how his old job has changed. During last year’s record drought, the remains of three cranes were recovered, but the total number of deaths was difficult to determine. That’s because biologists now employ a technique known as distance sampling to estimate the size of the flock. The new method, which is widely used to determine the populations of rare and endangered wildlife, doesn’t count birds individually, as Stehn used to do. Instead biologists fly aerial surveys during a predetermined time frame, and the cranes that are identified are recorded as a percentage to determine the population. However, according to guidelines, the two observers in the plane are not allowed to tell each other if one sees a bird. Nor does the pilot return, as Stehn did, and fly over a particular area again and again to search for missing birds in specific territories.
Stehn always believed that the results of his census were 97 to 98 percent accurate. He has read that the new method for estimating the birds is only 85 percent accurate. He thinks that between thirty and forty cranes could have died last winter, but nobody knows for sure. Current surveys put the refuge’s population at 245 cranes. That represents a loss of 38 birds from Stehn’s final census in 2010 and 2011, though the U.S. Fish and Wildlife Service* points out that it’s difficult to compare the numbers given the different methods of data collection and harsh drought conditions of the previous winter. “I think last year was a bad year,” Stehn said. “I’m frustrated that the refuge didn’t document that. They fell flat on their face.”
Stehn is concerned about more than the end of an annual count, though. He worries that invasive black mangrove and rising sea levels could wipe out the cranes’ marshes. Perhaps Stehn’s problem is that he stayed at the Aransas refuge too long, but after he arrived thirty years ago, he never left. Images of whooping cranes decorate his walls, his T-shirts, and his coffee mugs. Looking back at his career, he says, with a hint of wonder, “I just got enamored with cranes.”