[SBB] Slaty-backed Gull in Alviso!

["Alvaro Jaramillo" <[[email protected]]>]

Folks

   After a meeting at the EEC today I scanned the gulls from the parking lot
and noted a rather blackish-backed individual diagonally across the marsh,
sitting on the levee. The back was clearly darker than that of Western Gulls
in the area, my mind went immediately to Slaty-backed but it was still far
away. Legs were pink, and the head looked lightly streaked, largely white
which then got me on Great Black-backed for a second. But as it let its
primaries show, I could see that there was a lot of white on the folded wing
tip, with large white primary tips and a big mirror on P10. It stretched and
showed me the wing, a beautiful “string of pearls” pattern on the wing,
created by pale tongues on each primary! This in addition to the size, and
clearly not black (very dark grey) mantle secured the identification as
Slaty-backed for me. I rushed over to the levee and got closer and closer,
getting better looks and confirming that it had a yellow eye, reddish
orbital, and some thick blobby warm-brown streaks on the back of the neck
clinched it. I got some photos and was ready to sneak up on it for better
shots when a Harrier flew by and scared the group of gulls. The bird had an
amazingly wide white trailing edge to the wings, but since it flew directly
away from me I could not see the underwing pattern or much else. I followed
the bird in the scope and it flew towards one of the old landfill mounds
heading towards the Sunnyvale Sewage Treatment plant. Many gulls landed out
there, so there must be a large roost there somewhere. I would search there
or in the EEC levee area. I saw the bird at about 3:15 or so in the
afternoon. The best shot I got, plus a blow-up of the bird I posted on this
site: 

http://www.coastside.net/chucao/gulls/Slatyback.htm

It is not the best photo, but from what I saw it looked like a fine adult
Slaty-backed Gull! Good luck with it. 

Al

Alvaro Jaramillo
[[email protected]]
Half Moon Bay, CA

Field Guides - Birding Tours Worldwide
http://www.fieldguides.com/home.htm



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