The Legacy of James T. Tanner’s Ivory-billed Woodpecker Research
James T. Tanner was an ornithologist studying at Cornell University in the 1930s. His research focusing on the Ivory-billed Woodpecker is the only comprehensive study of this storied species. Searchers today reckon with his legacy.
Written by Mark A. Michaels, Research Associate
Every serious student of the Ivory-billed Woodpecker must acknowledge the legacy of James T. Tanner. Tanner’s was the only in-depth study of the species. That study and Tanner’s views—and the interpretations of his views—have shaped the discourse around the Ivorybill since the 1930s. If Tanner was generally right about the Ivorybill, it is almost surely extinct, as Tanner believed. Assuming the Ivorybill has survived, a careful, critical look at Tanner’s work may be crucial for understanding how and why.
In addition to studying Ivory-billed Woodpeckers in the Singer Tract, a large parcel of old-growth forest in Madison Parish, Louisiana (now Tensas National Wildlife Refuge), Tanner conducted a survey of the southeastern United States to assess the Ivorybill population across its range. That survey and Tanner’s estimate of the population in the late ‘30s has generally been accepted without question. This, too, has significant implications for the species’ survival.
Tanner first visited the Singer Tract in 1935 as part of a Cornell University expedition to record America’s birds, including its rarest species. The Ivorybill had been rediscovered there in 1932 after having been believed extinct for nearly a decade. T. Gilbert Pearson was the first ornithologist to observe the Singer Tract Ivorybills. He was guided by J.J. Kuhn, the Singer Tract game warden who would be Tanner’s guide in 1937 and ’38.
For Pearson, the experience was the culmination of a 50-year search. This bird was never easy to find, and Kuhn appears to have been the last person alive who could reliably do so. Tanner was hard-pressed to find Ivorybills without him.
Tanner returned to the Singer Tract in 1937, as a graduate student with a grant from the Audubon Society. He spent the next three seasons studying one family of Ivorybills there. His observations were published in the 1940s. His monograph became a kind of bible for Ivorybill searchers, despite the fact that it dealt with a limited number of individual birds (almost solely with only one family group) and despite caveats from Tanner himself that it should not be treated as definitive.
In addition to studying the Singer Tract birds, Tanner set out to singlehandedly assess and estimate the population of Ivorybills throughout the southeastern United States. He did this based on reports he collected, from suggestions from ornithologists, and on the historic record. He arrived at an estimate of 22 birds in the entire southeast.
There are issues with Tanner’s range-wide survey. As a practical matter, as heroic as the effort was, it is unlikely that that one individual could conduct a meaningful survey of the millions of acres of potential habitat in the southeast. Tanner was also doing most of his searching during the worst possible times of year, and most of his visits or promising areas were very brief.
Tanner’s own biases were also an impediment: he seems to have ignored reports from south-central Missouri, including one from an Audubon Society officer, possibly deeming the locations to be improbable. He was dismissive of reports from the vicinity of Avery Island, in part because he didn’t think the habitat was suitable, but also because of his apparent distaste for E.A. McIlhenny, an ornithologist from a different generation and cultural milieu. By contrast, Tanner accepted reports from people he respected, even if he found little other indication that Ivorybills were present.
Thus, it seems fair to argue that Tanner’s population estimate, heroic as it was, was less than accurate. By all indications, Tanner was tenacious, tough, dedicated, and meticulous as a fieldworker. And, his observations and the data he gathered at the Singer Tract are immensely valuable and beyond question. Problems have emerged in the interpretation, however, and Tanner bears some responsibility in this regard.
Tanner himself cautioned readers that they shouldn’t draw too many inferences from the Singer Tract study, because it dealt with one family of birds in one patch of habitat. He seemed to stray from his own advice, and his readers were even less careful. As a result, many questionable assumptions about Ivorybill behavior – from the food they eat to the habitat they require – have become accepted as truth.
The most notable misreading involves the Ivory-billed Woodpecker’s dependence on old-growth or “virgin” forest. Tanner would make this argument in later years, but it was clearly on his mind even when he was doing his surveys; he dismissed out-of-hand areas that he described as “cut-over.” In reality, as Tanner likely knew, some of the areas he considered “best” for Ivorybills at the Singer Tract, areas that had supported breeding birds, were predominantly second-growth. The belief that Ivorybills are old-growth obligates probably undergirds the assumption that the species must have gone extinct when the “last” such forest was cut. That’s what Tanner believed, and it led him to be dismissive of those who saw things differently.
Regardless of any personal feelings about Tanner, his towering contribution—and flaws in his work and its interpretation—are central to any discussion of the Ivorybill. As someone who’s convinced the Ivorybill has indeed survived, I’m now a little more interested in what he got wrong than in what he got right. What he got right will undoubtedly help us learn more about the bird, but figuring out what he got wrong may help us find it and to understand how it managed to evade being fully documented for so long.