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Renowned birder Kenn Kaufman attempts a fair-minded answer to the question of the Ivory-bill's existence:
https://www.audubon.org/news/ask-kenn-kaufman-ivory-billed-woodpecker-extinct
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ADDENDUM: In a comment below “John” references a graph of Hz levels for IBWO kents that didn’t make it into his comment. Here is the graph (and I assume this is based on the IBWO calls recorded by Cornell originally at the Singer Tract, but I'm not clear since it specifically references Mennill/Proj.Coyote data):