This intriguing first-basic gull was photographed November
18,2002 in Fort Worth, Texas by Martin Reid; the tone of gray
to the upperparts was distinctly darker than any nearby RBGU at
the same angle. I have studied - not just looked at - thousands
of RBGUs (usually it's the only gull I get to study), and I've
never seen an RBGU that looked darker than the norm. Small numbers
of first-basics are slightly paler than standard, but not darker.
While I feel the general structure and plumage is not much different
to RBGU, it is intertesting to note some similarities to Kamchatka
Gull (Larus (canus) kamchatscensis):- the darker mantle;
plain centers to the tertials (the thick white fringe to the 2nd-lowermost
tertial that ends before reaching the tip of the inner covert,
is classic Kamchatka Gull); the brownish tinge to the primaries;
and especially, the obvious greenish-blue color of the visible
tibia on the standing leg - again I've never seen this color on
a first-basic RBGU; even in late winter the most extreme variation
in RBGU seems to be a slight graying in the area, but never as
intense as on this bird:
Kamchatka Gull is extremely variable, as a browse of these
birds in Japan reveals. Given that I have found eight Mew Gulls
during my RBGU studies in Fort Worth, yet never seen a bird
like this one before, it seems more likely to me that this is
not a RBGU. It might be a hybrid RBGU x Mew, but could it be a Kamchatka
Gull???
