While birding the Duluth area yesterday, I made a stop at the Superior
Landfill. Since I am not great at gull ID, I took plenty of pictures to look
over later. There were very few gulls moving around, but at one point an eagle
passed over and many of the gulls that were just over the ridge flew up
briefly. When this happened, I started taking pictures of the flock without
really looking at the birds closely. This morning as I was going over the
pictures, I noticed an odd dark-backed gull in two of the photos, which I
believe may be a Slaty-backed Gull. The pictures can be found at the links
below.
http://s194.photobucket.com/albums/z43/GreatGray/?action=view¤t=DarkGull2.jpg
http://s194.photobucket.com/albums/z43/GreatGray/?action=view¤t=DarkGull1.jpg
I am using the following reasoning for the ID.
The solid color of the mantle and the pure white tail indicate an adult bird.
In terms of size, it is roughly equivalent to a Herring Gull. The gray of the
mantle is too dark to be a Herring Gull, but not dark enough to be a Kelp or
Great Black-backed. The black on the wingtips is not extensive enough be a
Lesser Black-backed. This essentially leaves Western Gull and Slaty-backed
Gull. The most compelling evidence for Slaty-backed Gull is the white
subterminal spot that can be seen on the third primary.
Please feel free to comment on or critique my reasoning. Especially if there
are any rare hybrids or color abnormalities that appear similar to the bird in
question.
Good birding,
Josh Christian
Hutchinson, MN
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