Peter Pyle and Michael Retter Discuss Checklist Changes

 

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Birding is “just” a hobby perhaps, but birders sure are knowledgeable about the recondite matter of avian taxonomy. We birders groan when bird species are “lumped”—and ticks are removed from our life lists. Conversely, we jump for joy when ornithologists “split” bird species. Or do we? Molt and ID expert Peter Pyle, in a commentary in the print version of the September 2012 Birding (pp. 34–39), is wary of the recent spate of species splitting. Winging It Editor Michael L. P. Retter is more sanguine, however, about recent checklist changes (see Birding, September 2012, pp. 30–33). Meanwhile, Birding Editor Ted Floyd just likes a good fight.
    Bring it on, guys!

Moderator Ted Floyd: Michael, I sense from your “Check-list Redux” (pp. 30–33) and other recent writings that you basically “approve”—for want of a better word—of recent splits. Peter, your take is different; your memorial to the avian species (pp. 34–39) is cautionary, even critical. Could you two offer your very basic views—in 150 words or fewer, please—of recent splits?

Michael Retter: By and large, after reading the corresponding scientific literature, I do “approve” of the 2012 American Ornithologists’ Union (AOU) splits. (That’s not to say I approve of all splits.) Conservation is a certain (and worthy) benefactor of splitting, but in the end, science marches on, no matter what. Detailed DNA analyses were not possible in 1983. Neither was the iPhone. Should we really get in the way of science just because we’re not comfortable with change? Surely we should look at each potential split on a case-by-case basis. If science takes us down the splitting road, why is that bad? I do find it somewhat humorous that molt guru Peter Pyle proposes that we “might go back to the taxonomy of the 1983 AOU Check-list.” I doubt he would also suggest stepping back into the 1980s with regard to molt terminology (“eclipse,” “nonbreeding,” “first winter,” “second calendar year,” etc.).
    By the way, I completely agree with Peter regarding Western Flycatchers. That split and the paper on which it was based were, in my opinion, the epitome of what I (controversially) refer to as “sloppy science.” Let us next discuss “Northwestern” Crows...
    Left: Photo by Mike Freiberg. 

Peter Pyle: A lot of blood, sweat, and tears have been shed over the definition of a bird species, and over the taxonomic line between subspecies and species. While this theoretical line has taken broad swings over the 200-year history of species concepts, a recent trend toward splitting seems to be establishing new ground. Since 1983 the AOU has split 148 species of North and Central American birds while lumping only 9, and this imbalance between splits and lumps seems only to be accelerating both here and in Europe. This recent trend, while fueled by advancements in molecular and audio-analytical techniques, has been fundamentally influenced by human opportunism: Splitting is more “exciting” than lumping. It may be just be a matter of perspective and holistic need (e.g., for conservation reasons), but a fixed line seems more useful and scientifically tenable to me than one that shifts—at the moment toward species-splitting mania.
    Right: Photo by Martin Meyers. 

TF: Michael, you’re a brilliant editor, but we need to work on your counting skills (“150 words or fewer, please...”). Peter, I’m gratified but not surprised that your answer is 150 words on the nose. But let’s get back to the conversation. Peter, you see opportunism where Michael sees progress. Basically, I see it Michael’s way. Great thinkers like Copernicus, Darwin, and Einstein broke “fixed lines” (Peter’s wording) right down the middle. My question for Peter: Is progress in avian taxonomy a good thing? If so, what kind of progress would you like to see in the next decade? Michael: You mention Northwestern Crows. Everybody says they’re just a subspecies of the American Crow, yet the Northwestern Crow remains stubbornly unlumped. Why is that? Does Peter have a point? (Guys, same routine: 150 words or fewer.)

PP: I think we’re approaching the question from different levels of perspective—advancements in understanding vs. definition of concept. Of course I am in favor of taxonomic advancements, and am as excited as others about new molecular findings. Recent advancements in higher-order taxonomy (genera, families)—for example, the finding that parrots and falcons are relatively closely related to each other—in retrospect matches other things we know about these taxa, including molt. But these advancements haven’t changed our definition of higher-order taxonomic concepts, just as H-P terminology doesn’t change the fundamental definition of “molt,” or advancements in porcelain technology haven’t changed our definition of “toilet”—thought of that while peeing just now. [Wow. Talk about multitasking. —TF] While future advancements may reveal new species limits, in crows for example, the definition of species needs to be stable, for the benefit of scientists and non-scientists alike, or our evaluation of objective taxonomic advancements could be obscured rather than enlightened.

MR: Have higher-level taxonomic definitions really been static? Take the class Reptilia. Thanks to DNA, we know that birds are a kind of dinosaur and that mammals are related to synapsid reptiles (like the impressive Dimetrodon, the one with the crazy sail on its back). None of these is closely related to turtles, lizards, or crocodilians. What constitutes a class had to be reevaluated in the light of genetic evidence. To go in another direction, quantum mechanics and general relativity turned the world of physics upside down. Most of us think that gravity is a strong force that pulls things together. So did Newton, who defined gravity with his tidy inverse-square law. Physicists now understand gravity instead be a spacetime curvature, a very weak force likely transmitted by a massless particle, the graviton. Our definition of gravity has changed markedly in the past century. Why not our definition of species?

TF: Let’s for now stick with the ornithological gold standard of the Biological Species Concept (BSC). I suspect we agree that reproductive isolation is a key aspect of the BSC. Various things isolate species: DNA, of course; timing (“phenology”) of the breeding cycle; vocalizations and other behaviors; and morphology. If populations in the Band-rumped Storm-Petrel complex are reproductively isolated by DNA, phenology, and vocalizations, that’s cool. And if the reproductive isolation is strong, then they’re multiple species. That’s new knowledge, but it’s not a new species concept, is it? Isn’t it still the BSC—but with a newfound appreciation for the importance of previously unknown (DNA) or under-appreciated (behavior, phenology) causes of reproductive isolation?

PP: Again, I don’t disagree with either Michael’s or Ted’s points here about definitions of species and higher-level taxa. My point is that I want the avian taxonomic framework to remain stable and solid. If we do eventually find out that Band-rumped Storm-Petrels are reproductively isolated to the satisfaction of the BSC, fine: I’d accept three or four or ten or whatever number of species may be involved. My worry is that our collective eagerness to spilt species is causing us to make these decisions prematurely, as I believe occurred with Western Flycatchers. But what concerns me even more is that human opportunism is adding pressure to move and shake the legs of the framework, which could cause it all to fall down—something that Ted gets at in his online essay. Now I’m hearing of two species of Wilson’s Warblers, but the split, between central and eastern rather than central and western subspecies, is not where I’d expect it based on phenology, vocalizations, breeding timing, and so on. Again, I’m left with the feeling that human tendencies are torpedoing what should be an objective avian species concept.

TF: I think I’m okay with what both of you are saying. Michael likes intellectual progress; Peter is wary of opportunism. No contradiction there. Thanks, guys, and let’s move onto something else. Believe it or not, I’m going to advocate here for a lump—Golden-winged and Blue-winged warblers. That’s right, I seriously wonder whether they’re one species. What do you say to that? If I’m right, would that result be somehow “bad” for bird conservation? (And, again, can we keep the responses to 150 words?)

MR: This is why I’m opposed to adopting the BSC wholesale. The warblers readily interbreed, producing fertile hybrids—just like Western and Glaucous-winged gulls, Baltimore and Bullock’s orioles, and Indigo and Lazuli buntings. Yet I’m aware of no serious proposals that they be lumped, as the BSC would proscribe. Instead, the AOU has [...]

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The rest of this conversation is tremendous fun. Michael Retter and Peter Pyle offer fascinating insights into everything from Cassiar Juncos to Bryan's Shearwaters to Dusky Seaside Sparrows; from the correct orthography for jaçana to the proper use of the apostrophe vis-à-vis eponymously named bird species. You'll learn a great deal from these two experts, and you'll laugh out loud at their wit and charm. But not here. To eavesdrop in on the rest of the conversation, you need to be an ABA member.

 

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