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possible |
 Fig 1) We're less sure about this one. Is it a large male Thayer's Gull? There's next to nothing in plumage differences to go on here, so we're left with head, body, and bill size and shape, which are not so conclusive here. |
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| Fig 2) The inner webs of the outer primaries are fairly dark here, more like what we would expect from Herring than Thayer's, though the overall dark color is a shade lighter than the near-black of Herring's outer primaries. The underwing is quite silvery white, more like Thayer's and Glaucous-winged. |
Fig 3) This reveals the tail, showing the pale barring at the base
of the outer retrices, typical of Herring and Thayer's. The underside
of the outer primaries have a dark trailing edge, a bit thicker than
normally seen in Thayer's. This is not seen in Glaucous-winged, but
could reasonably be present in a hybrid.
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Fig 4 and 5) Fig 4 reveals the bill size and shape-- a bit large and thick
for Thayer's (?), but still with little gonydeal angle. Combine this
bill with the primary pattern and one may conclude this is a Slaty-backed
Gull. However, the well-checkered greater coverts (see Fig 1) and
the lack of prominant dark terminal spots on the inner primaries (in Fig 5)
point against Slaty-backed.
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