[cobirds] Re: M Ducks

Thanks, Steve, for this valuable summary. Just a few things to add:

Along with Mexican, Mottled, and Mallard, we should be on the lookout for a fourth "M" duck, namely, the red-blooded Murican Black Duck. :-)

Steve raises an important point about bias. Those of you who were at the WFO conference in Pueblo in 2017 may recall that Andrew Floyd gave a presentation on this very matter. Andrew extended Steve's caution to the broader problem of "the I-25 bias," depicted in this figure:

(Don't worry your pretty little heads over why that slide shows hybrids. It was all spelled out in the presentation. Besides, the previous slide showed presumptive purebreds.) Anyhow, the I-25 bias is at least as acute in New Mexico as it is in Colorado. Note also that there are a fair number of reports from in and around the San Luis Valley--which is not to deny Steve's main point. Indeed, it sort of makes Steve's point.

Andrew also discussed time-of-year biases, shown in this eBird graph of Colorado Mallard detections, which is almost certainly the product of temporal observer bias, not actual Mallard biology:

Finally, Steve mentions Mallard x Mottled Duck hybrids. Here's a relevant slide from Andrew's presentation:

May I venture a prediction? Here goes: Mexican Duck is the new Thayer's Gull. What I mean is, Mexican Duck is "the next big thing" in hair-splitting, hair-pulling, hair-graying delight for those who, well, delight in such matters.

By the way, I was working outside during the overnight hours this Monday morning, Aug. 20, and I heard several Lark Buntings on nocturnal migration over Lafayette, eastern Boulder County. The birds had to land somewhere, perhaps in Boulder County. Anybody seeing them "on the ground" today?

Ted Floyd

Lafayette, eastern Boulder County

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