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Posted by Robin Diaz on 08:31:00 11/28/14
In Reply to: Re: Tropcial Kingbird and more posted by steve siegel
Steve - I have nothing sage to add but I imagine with calipers, the distinction can be made in the hand. The shape of p10 is different for Tropical Kingbird Vs. Couch's. The photo shows p10 on the Virginia Key bird, which is the shape of Tropical Kingbird.
Here are the challenges: Peter Pyle uses "usually" and "more study is needed" and "details to be worked out." He also uses a scatter graph for plotting bill measurement divided by wing chord against wing formula equation, to separate Tropical from Couch's Kingbird. Not only are some of the two species very close to each other on the graph, but Pyle notes: "... the criteria presented ... apply to AHY/ASYs [adult birds] only; more study is needed on HY/SYs [young birds]." (Are your eyes spinning yet?) If you throw this into the pot along with the three geogrpahic variations of Tropical Kingbird, you get a stew of information.
On a personal note, I attended a workshop in CA led by Peter Pyle and Debi Shearwater and Pyle discussed his and his father's 8-year journey in writing _Identification Guide to North American Birds Part I_. He expressed disappointment in many of his sample sizes, which were often, strictly museum specimens.
This doesn't help answer the question regarding Larry's photo grab but it does bring up the issue of absolutes used in identifying some of these birds in the field. Perhaps Bill Pranty will weigh in here, as I believe he's currently researching Tropical Kingbirds in FL?
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