Slaty-backed Gull—Superior, WI landfill

[Karl Bardon]

I watched gulls at the Superior, Wisconsin landfill
today from approximately 10:00-15:00 and saw the
following:

At least 680 Herring Gulls, eight Glaucous Gulls (5
first-cycle, 1 third-cycle, and 2 adults), seven
Thayer’s Gulls (2 first-cycle, 2 second-cycle, 3
adults), and three Iceland Gulls (1 first-cycle, 1
third-cycle, and 1 adult). The number of birds
(especially Herring Gulls) is likely much greater than
posted, since there is a constant influx and outflux
of gulls, and since I only counted the number of each
age seen at one time, or new individuals that I could
recognize based on plumage differences. The majority
of gulls were identified in flight since the landfill
is closed to the public and viewing can only be done
from outside the fence.

Also seen and photographed was an adult Slaty-backed
Gull. The latter was studied off and on for several
hours both perched and in flight, and showed the
following: size of large Herring Gull with overall
bulky structure and large bill, yellow irides, pink
legs, heavy head streaking that formed a distinct bib,
broad white tertial crescent, slate gray mantle, and a
“string of pearls” effect formed by white subapical
tongue tips on primaries 6-8 (dorsally and ventrally).
When the bird flew directly overhead, I was able to
see a large white subapical mirror on primary 10 (the
outermost), a moderate sized white window on primary
9, and subapical white tongue tips on primaries 6-8.
When the bird was perched with the underside of
primary 10 showing, this feather appeared medium gray
except a large white subapical mirror, a narrow
darksubterminal bar, small white apical spot, and a
distinctly dark, narrow outer web.

Karl Bardon


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