Herrings. They never bore. Here's a 2nd cycle from Michigan City, Indiana - 02 November 2014:
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Although the bill is slightly open here, the "feel" was very Glaucous-like. |
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The underwing linings have the brown and white dotting that I associate with Great Black-backed. |
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The very fine stippling on the upperwing coverts is noteworthy. |
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Heavy, barrel-shaped body much like a Great Black-backed or Glaucous. |
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When averaging all of the photos, this photo is closest to what the upperparts looked like in the field. |
I've observed pale Herrings similar to this one in California but late into the winter season after, presumably, bleaching had set in - the upperparts to those birds show very little pattern to the upperwing coverts (unlike the Michigan City bird).
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Herring Gull (2nd cycle). Half Moon Bay, CA. 18 Jan 2014. There's little doubt that the upperparts are bleached. |
Here's the open wing of the bird above:
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P6-P8 show tear-drop like pale inner webs (left wing). The very plain, white, greater coverts are bleahced. |
Now the open wing of the Michigan City bird:
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The greater covets show a pattern and have not bleached or faded. Interestingly, this bird too shows pale tear-drops at the subterminal portions of the innerwebs to the outer primaries. |
Assuming the 2nd prebasic was just recently completed, I have to rule out bleaching as an explanation for the pale upperparts. It could very well be a slight melanin deficiency, or outside influence - perhaps Great Black-backed or Glaucous genes somewhere in its ancestry (the larger barrel-shaped body and large bill were striking).
Or, is this plumage aspect completely within the range of variation for Smithsonianus?