This "white-winged" gull was photographed at Corpus
Christi Landfill on March 20, 2004 by Martin Reid and Willie Sekula:
it was the size of a small HERG, and quite daintly-looking, due
to the rounded head and delicate bill:
A most confusing bird for me; here's my initial thoughts:-
Not a GLGU (many things wrong); nor a pure ICGU
(structure, tail pattern, etc.), nor a normal HERG that
has faded/worn (too much pale tones in coverts and retrices; markings
in greater coverts too irregular; subtle subterminal mottling
in some retrices.) Leucistic HERG?: maybe, but the degree of patterning in
all the feathers does not look right for such a creature, I feel.) Nelson's Gull (GLGUxsmith HERG)?: should have a
cleaner bicolored bill, more obvious whitish eye-crescents, more
barring in the tail base, plus the bill size and overall size
look too dainty for this combo? GLGUxGWGU?: not large enough or chunky enough, and too
much dark in primaries? GWGUxHERG?: not large enough or chunky enough, and wings
too pale - although the rather short-winged look and almost-plain
tail suggest this combo? HERGxTHGU?: Structure may fit, but flight feathers look
too pale for this combo? HERGxICGU?: in some ways this seems the best fit (size,
structure, paleness, tail pattern) - but do such hybrids exist?
most range maps show smith HERG meeting kumlieni
in southern Baffin Island - ??? THGUxICGU?: seems too large and chunky (but bill shape
okay?), and the almost-plain tail seems wrong?
addendum, March 25: THGU?: this has been suggested, yet I wonder if
a pure THGU ever shows this extent of marbling on the greater
wing coverts, lower scaps, and retrices (see iamges below) ?
Update: March 25: Here's a
new image from March 20:
- on the crop below, note the marbled pattern in the arrowed feather,
plus the large number of 2nd-generation scapulars:
and here's a couple of pics by Willie Sekula from March 24:
note below the fine marbling in the distal outer web of each retrix:
