Exchanges with Chuck Hunter in a private Facebook group and in conversation inspired this addendum. If you haven’t read the original post, 2023 in Retrospect (Part 4): Acoustic Data in a Visual World, I encourage you to check it out first. Chuck’s comments led me to reconsider Tanner’s response to the Dennis recording, which resembles Peter Paul Kellogg’s more closely than it seems at first glance.

I have known for years that Tanner had a low opinion of Dennis and that Dennis could be erratic. I was unaware that many professional ornithologists had doubts about Dennis’s competence and honesty. It turns out that Kellogg and others at Cornell shared those doubts and that Kellogg’s comments on the Dennis recordings reflected them. (I suspect Kellogg’s stated concern about a third party doing playbacks was a diplomatic and defamation-avoidant way of suggesting chicanery.) 

As Chuck wrote:

While not explicitly written down officially by Cornell officials (that I’m aware of anyway), the following excerpt from Don Moser’s 1972 Life article is a reference (I am told from others who were at Cornell at the time) to Kellogg’s actual opinion of the Dennis tape, “The recording was of such poor quality that it was not accepted by the scientists who analyzed it, and indeed, one of them said that it was suspected as a phony, since played at slow speed it sounded like a pencil being rolled across a table. The idea of straightforward Dennis rolling pencils to create a faked record is beyond the bounds of credibility. Even the scientists agreed that such shenanigans, given the man, seemed unlikely.” As with other discussions on sounds and sightings, I agree such suggestions of fraudulent evidence from Dennis would in my opinion seem unbelievable, but can’t be thoroughly dismissed either.

While as Chuck stated, fabrication can’t be thoroughly dismissed, there are compelling reasons to consider it most improbable. There have been ivorybill hoaxes in the post-Singer Tract era. I have personal experience evaluating evidence that I reluctantly deemed fabricated. At the same time, the mere allegation of fraud seems to lead to an (almost) irrebuttable presumption thereof . . . because the ivorybill ‘must be extinct’. This characterizes the treatment of the Fielding Lewis photographs, the Dennis recordings, and the Agey and Heinzmann feather (about which there may be more reason to harbor doubts).

The doubts about Dennis’s credibility had some basis. As I see it, they were due in part to elitism among academic ornithologists. (Dennis did not complete his Ph.D.) They also seem to have resulted from Dennis’s “lack of social skills that led to misunderstandings”, per Chuck. Ironically, Tanner’s nasty response is one of the strongest indicators that the Dennis recording is authentic.

Tanner said nothing about the Dennis recordings until 1974, six years after the date of the encounter. When he did weigh in, apparently under pressure to comment, he wrote:

Thank you for sending me the tape of the recording made by Dennis. I have listened to it carefully several times over an interval of two weeks. I agree with you that it does sound like the note of an Ivory-billed Woodpecker and that it is not similar in pattern to the record [1935 recordings]. The notes on the tape are peculiar in their monotony, several single notes at the same pitch, because the birds usually called a series of single and double notes, varying in pitch. The Cornell record illustrates this. If it was an Ivory-billed, I have two questions. What was the bird doing in the same habitat with a Pine Warbler? If it was close enough to be recorded with a simple microphone, why could it not be seen and followed?”

As previously noted, the comment about Pine Warbler as an indicator of unsuitable habitat was absurd. Tanner should have known better. Pine Warbler is even on the checklist for Tensas National Wildlife Refuge, formerly the Singer Tract. (It is listed as rare in summer, fall, and winter, p. 213.) A close examination of Tanner’s other comments on Dennis strongly supports ivorybill as the source of the calls. In conjunction with his actual observations, they effectively exclude fabrication. Tanner’s most salient comment, mirrored Kellogg. He wrote, “I agree with you that it does sound like the note of an Ivory-billed Woodpecker and that it is not similar in pattern to the record. (Emphasis added.) The fact that the recording includes normal Pine Warbler and Northern Cardinal vocalizations strengthens the case for its authenticity.

Tanner’s next statement about monotony and his claim that ivorybill calls are “a series of single and double notes, varying in pitch” reflect what is on the 1935 recordings (and no doubt what he remembered). But the statement conflicts with what he actually observed in the 1930s. Tanner described ordinary ivorybill vocalizations in the monograph. He wrote,”The kent note, given in monotone and slowly or infrequently, is the ordinary call note. When the bird is disturbed, the pitch of the kent rises, and it is repeated more rapidly, frequently doubled, kent-kent . . .” (p. 62). This thoroughly refutes his objection and also refutes the idea that this could be playback or fabrication.

Years later, Tanner revisited his field notes and provided an answer to his question about following the sounds. This approach that sometimes worked for Tanner with birds habituated to his presence. But it often failed, even with those birds. In “A Postscript on Ivorybills” (Bird Watcher’s Digest, 2000), Tanner described some of those difficulties. He wrote that,”Finding and following ivorybills was a fascinating game, and when the chase was successful, had a fitting reward . . . ” He went on to discuss the ease with which he found the 1938 nest and the challenges he faced in 1939. In that season, Tanner lacked Kuhn’s expert assistance. And of course, he only ever found one other ivorybill in the Singer Tract.

Thus, both Kellogg and Tanner – the two then-living individuals best qualified to make the judgment – identified the source of the sounds as (at worst) consistent with Ivory-billed Woodpecker. They did not suggest alternatives. Multiple factors tend to exclude fabrication or inadvertent capture of playbacks. Still, it’s self-evident that neither the Dennis recordings nor the Courtman recordings will be accepted as “proof” in their own right. Indeed, they have not been. This is due to the extremely high standard that exists for the ivorybill, not the quality of the evidence itself. For the Courtman recordings, the number of calls, the duration of the encounter, and the co-occurrence of double knocks militate for ivorybill as by far the most plausible explanation.

Together, I think the Courtman and Dennis recordings afford much greater insight into what ivorybills sound like under ordinary field conditions than the ’35 recordings. Despite Tanner’s dismissive intentions, his comments strongly support this interpretation, perhaps even more strongly than Kellogg’s.