Posted by Phil Pickering (126.96.36.199) on August 13, 2000 at 08:45:26:
Sorry if this is excessive posting on one bird, but a couple thoughts have recently coalesced, thanks to this quiz, that might be of interest to gull enthusiasts as things to look for/at in the future, or comment on if their experience is otherwise.
- I personally don't recall ever seeing (in Oregon) a Glaucous-winged with a bill that appeared this clean and mature-looking that *also* did not have fully-mature adult-like coverts. I'm sure it's possible, but my impression is that the bill is the last thing to appear this mature on the vast majority of GWs.
Based on some limited experience and study of numerous photos, it is my impression that this is often not the case with Glaucous. It appears that the combination of a mature or nearly-mature appearance of the bill *and* retained immature coverts (as in this gull) might be a decent mark for separating Glaucous from GW. I'm not sure if this is because Glaucous has less black to fade on the bill, or because Glaucous just takes longer on average for the coverts to fully mature (maybe something to do with it being an arctic-nesting species?)
-The appearance of the bill-tip on this gull may be a very good mark for Glaucous at this age (3rd-year+). To get obsessively fine with this, it is my impression that the black on the bill-tip of Glaucous will often fade into two distinct "spots" on the tips of the upper and lower mandible, nearly or completely separated by noticeable fading along the cutting edge. This is another thing I don't recall seeing on GW. My impression is that the black on the tip of GW will typically fade into a large spot mostly on the lower mandible, or often into a solid subterminal band. The black along the cutting edge near the tip typically does not seem to fade before the bill fully matures, as it often seems to in Glaucous.
Again, I'm sure it's possible a GW could have any one of these attributes. However, when you combine (for a nearly-mature pink-foot) apparently clean-white primaries that don't appear to show an extreme amount of wear, extensive clean-white in the tertials, apparent total lack of dingy-grayish or brownish tones in the primaries and immature coverts, bill apparently maturing before coverts, Glaucous-like fading of the black on the bill, pronounced eye-arcs, pale iris, and head-shape, bill-shape, and primary projection that (in my opinion) would seem to fit barrovianus Glaucous better than GW, I haveta conclude this gull is a Glaucous.
Out on a limb in Oregon.
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