A few months ago I wrote about a mysterious new “whit-beert” call that I had discovered in the bowels of the Macaulay Library’s online collection, and which I took to be a previously undescribed sound of Yellow-bellied Flycatcher.  Noticing a certain resemblance to the “dew-hic” call of Dusky Flycatcher and the “peer-pewit” call of Hammond’s Flycatcher, I concluded that the new call was likely homologous with those sounds — that is, that the “dew-hic,” the “peer-pewit”, and the “whit-beert” are all evolutionarily derived from a similar call given by the species’ common ancestor.

Now, new information has come to light that calls my earlier conclusions into question.  First of all, Empid guru Arch McCallum told me he wasn’t convinced that the “whit-beert” was equivalent to “dew-hic” and “peer-pewit”, due to the different spectrographic shape of the “whit” and the fact that it was never repeated.  Instead, he pointed out the similarity of “whit-beert” to certain calls of Willow and Alder Flycatchers.

He may have hit the nail on the head.  I recently discovered a second recording of the mysterious “whit-beert,” from western Maine, labeled as an Alder Flycatcher.

“Whit-beert” call, labeled as Yellow-bellied Flycatcher. Woodhull Lake, New York, 5/30/1998. ML catalog #106901	“Whit-beert” call, labeled as Alder Flycatcher. Upton, Maine, 6/2/1962. ML catalog #7546

The new recording was taken in 1962, before “Traill’s” Flycatcher was split into Willow and Alder. The recordist was Dr. Robert C. Stein, who had already realized that “Traill’s” sorted into two vocal groups, and was in the process of collecting data for his classic 1963 publication that provided the first strong evidence for the eventual species split.  The notes on the recording indicate that the recording was made during a “hostile response to playback,” but it doesn’t say what sound was used for playback, nor does it explain how the recording was identified as an Alder Flycatcher.

So: which species is it that gives the “whit-beert” call?  Personally, I agree with Arch that Yellow-bellied is probably the least likely culprit.  Alder is the leading contender at the moment, followed by Willow.  But to answer the question definitively, I think we’ll need some more recordings.

If you’re interested in helping to solve the mystery, you might try some playback experiments in northeastern North America this spring.  Does playing “whit-beerts” to an Empid elicit more “whit-beerts”?  What species says “whit-beert,” and what is the behavioral context of the sound?

I don’t think anybody knows the answer to the questions I just asked.  I don’t think anybody has ever known.  But they could be easily answered by anyone with an audio recorder and a couple of spare hours in New England this summer.

This is what I love most about bird sounds — the tantalizingly short distance to the frontier of knowledge.