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Message: <blockquote data-quote="Kirk Roth" data-source="post: 1852731" data-attributes="member: 85015">This sentence caught me:"Differences between Nearctic and Palearctic subspecies can be slight, mainly involving clustered averages in biometrics and body size, as in Red-necked Grebe, or more obvious plumage differences, as shown by Sandwich Tern."The Sandwich/Cabot's Tern split is one that hasn't set well with me, mostly because they seem so similar to me.  I'll grant that this is based on limited and amateurish research and that I've not yet sailed across the pond to see a European Sandwich Tern.  When Callahan talks "obvious plumage differences," do you think he's referring to the yellow-billed South American populations vs. the European?  Or is there some other glaring difference that I'm blind to?I've been under the impression that the major difference between Sandwich and North American Cabot's has been size difference, and not all that striking.  That, and the Cabot's greater affinity for Elegant Tern genetic code (a difficult field mark, indeed).  What else?</blockquote>