[TopOfUtah] Another "white-winged" gull in Logan - possible ICELAND GULL?

[Ryan O'Donnell]

I initially identified the bird that Jason Pietrzak posted about
yesterday as a Glaucous Gull on the basis of its pale overall pale
color, pale wingtips relative to the wing, and bicolored bill with a
distinct dark tip and pale base.  But some aspects of the head and bill
shape made me doubt that initial identification, so I went out to look
for the bird last night and again this morning.  Last night Jason and I
found a DUNLIN and relocated the AMERICAN GOLDEN-PLOVER, but not the
gull.
 
This morning, Craig and I relocated the gull in question on the
Shorebird Playa at Sue's Ponds, just west of the Logan Landfill.  I feel
confident now that it is NOT at Glaucous Gull, but I'm not sure yet what
it is, so again I'm soliciting your input.  The bird is too small for a
Glaucous Gull, being intermediate in size between California and Herring
Gulls, both of which were nearby for comparison several times.  Also,
its head was too small and rounded and its bill too slight.  Photo 7
below shows the gull in question (back center) next to a Ring-billed
Gull (far left), several California Gulls, and a Herring Gull (far
right) for comparison of size.  Thayer's Gull would be a likely guess
for this bird at first glance, but a few things give me pause about that
conclusion.  The bill is very clearly pink at the base and dark at the
tip, but the mantle was not a solid gray of any tone, rather a mottled
brownish typical of first-year gulls.  This probably indicates a
second-year bird that still has its first-year mantle.  Thayer's Gulls
do not retain their mottled-brownish mantle into their second winter,
although Iceland gulls often do (according to Kaufman's "Advanced
Birding").  The primaries and tail were very pale, not contrasting with
the rest of the wing.  Also, the primaries do not seem to have the
bicolored "striped" pattern that is supposed to be diagnostic for
Thayers.  Finally, this bird seemed paler than the palest Thayer's shown
in Sibley and paler than the palest fresh-plumaged Thayer's in Howell &
Dunn ("Gulls of the Americas"; although the spring Thayer's in bleached
plumage is about the right shade, this bird was not worn and bleached
like a spring bird could be.).   Although I know it is very unlikely
based on distribution records, these traits taken together make me
wonder if this is an ICELAND GULL (in the broad sense, including
Kumlein's), which has a smaller bill than Thayer's, paler colors in the
body, paler wingtips, and lacks a bold tail band.
 
Here are some of the best photos I have.  I have a few more, but I think
these are the ones that show the key features best.  The first nine were
taken by me, the last two were taken by Jason Pietrzak.  (Jason, I hope
you don't mind me posting these for you.)  If anyone gets back out there
and can relocate the bird, I think it would certainly be worth getting
some more shots.  A better shot of the spread tail would be particularly
helpful, I think.
 
http://i110.photobucket.com/albums/n105/Tsirtalis/GULL1-1.jpg
http://i110.photobucket.com/albums/n105/Tsirtalis/GULL2-1.jpg
http://i110.photobucket.com/albums/n105/Tsirtalis/GULL3-1.jpg
http://i110.photobucket.com/albums/n105/Tsirtalis/GULL4-1.jpg
http://i110.photobucket.com/albums/n105/Tsirtalis/GULL5-1.jpg
http://i110.photobucket.com/albums/n105/Tsirtalis/GULL6-1.jpg
http://i110.photobucket.com/albums/n105/Tsirtalis/GULL7-1.jpg
http://i110.photobucket.com/albums/n105/Tsirtalis/GULL8-1.jpg
http://i110.photobucket.com/albums/n105/Tsirtalis/GULL9-1.jpg
http://i110.photobucket.com/albums/n105/Tsirtalis/2.jpg
http://i110.photobucket.com/albums/n105/Tsirtalis/3.jpg
 
 
Good birding,
Ryan
 
Ryan P. O'Donnell
Department of Biology and the Ecology Center
Utah State University
5305 Old Main Hill
Logan, UT 84322-5305
 
http://200birds.blogspot.com