Comments on a Possible Kelp Gull or Kelp x Herring Gull Backcross
by Ed Hopkins, West Lafayette, Indiana, USA
An mystery gull of sorts was observed on the Lake
Michigan beach in Indiana Dunes State Park (SP) on
16 October 2004 until 9:30 AM. The park is located in northern
Porter County, Indiana, USA,
about 1.5
miles north of Chesterton at the end Highway SR49.
What was, initially, thought to be a Greater
Black-backed Gull. It stood on the beach about 400 yards east
of
our position, which was on top of the park's bath house. It might have,
first, been sighted around 8:00 AM.
An adult
Lesser Black-backed Gull and numerous Ring-billed and Herring Gulls (HERG) lined
the beach directly
to our
north.
The black-backed bird worked its way to a
position straight north of us. When it joined the flock of mixed
gulls, we noticed that it was the same size as the Herring Gulls. The bird's
legs were a bluish-tinged gray color.
It had a band
on the left leg. Its bill was thicker than nearby Herring Gulls. It
had small white tips to the black
primaries. The
outer primary, p10, was blackish on the underside and had a white mirror or oval
shaped area
about an inch from
the tip. The bird's head was much flatter than the nearby Herring Gulls.
The angle starting at
the base of the bill
was very shallow. The ridge over the eye was very pronounced giving the
eye a "mean" or
squinting appearance.
The eye was light, but I could not be certain that is was yellow. The
head, tail and under
body were an unmarked
white color.
When the bird flew away from some beach walkers, the
flight feathers appeared black. Primaries, p1 through
p5 or p6, had been molted. The wing looked rather paddle shaped because
the most recently replaced primaries
were shorter. The trailing edge of the secondaries formed a narrow, white
border. The wing coverts and back
were a very dark-slate black color.
Our first though was that the bird was a Kelp Gull (KEGU)
or a backcross of some combination of Kelp Gull
and Herring Gull. See a discussion of the Louisiana birds on the web page
at:
http://losbird.org/los_news_181_98july.htm
The only deviating field mark for Kelp Gull that we noticed was the narrower
than expected trailing edge to the
secondaries. I was in the company of Ken Brock, Susan Bagby and John
Cassady. You can form your
own opinion from the following digiscoped pictures.
Fig. 1 - This is a side view of a possible KEGU or backcross that was digiscoped
at Indiana Dunes SP on
16 October 2004. It is in the company of two HERGs which are similar in
size to it.
Fig. 2 - This is an exploded and brightened view of the primary tips on
p7-p10 on the possible KEGU or
backcross. The upper side of the tips have minimal white. The under
side of p10 has a whitish oval about
an inch from the tip.
Fig. 3 - This view of the possible KEGU or backcross shows the bluish-tinged gray legs.
Fig. 4 - This another view of the possible KEGU or backcross shows the
bluish-tinged gray legs and the band.
If we were only closer and could have read the band to what information would it
have led us?
Bibliography -
Cassady, John, "Mystery Gull"
(Adult) - Indiana Dunes State Park, Chesterton, Indiana - October 16, 2004,
http://www.jkcassady.com/gallery/oddgull.htm
Dittman, Donna L. and Cardiff, Steven W., Kelp Gull and Herring x Kelp Gull
hybrids: a new saga in gull ID
problems, http://losbird.org/los_news_181_98july.htm
Olsen, Klaus M. and Larsson, Hans, Gulls of North America, Europe, and Asia,
Princeton University Press,
Princeton and Oxford, 2002 (recalled volume), pages 141-150