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David Sibley

The mystery of the orange-throated hummingbirds

Update 16 August: a new post Progress on the orange-throated hummingbird mystery. Update 14 Aug 2011: A follow-up to this post is now available, tempering some of these points and adding more questions – Orange-throated Hummingbirds: more questions. Every year in August and September, a few perplexed observers in eastern North America send out questions about

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Can Short-tailed Shearwater be identified in the field?

Usually. Experienced observers can almost always identify these species correctly based on careful judgment of head shape and bill size, but these are subtle and subjective impressions, and require a foundation of experience and/or direct comparisons with Sooty. Other features can offer supportive clues or draw attention to a potential Short-tailed, but are not very

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Distinguishing Eurasian and American Common Merganser

The Eurasian subspecies group of Common Merganser, known by the English name Goosander, has occurred numerous times in the Aleutian Islands of western Alaska, but has never been identified farther east in North America. The American subspecies has some potential to wander to Eurasia, but has never been recorded there. I’ve never seen any in-depth

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