[obol] A Primer on Adult Gulls in Flight -- a photo gallery
- From: David Irons <llsdirons@xxxxxxx>
- To: OBOL Oregon Birders Online <obol@xxxxxxxxxxxxx>
- Date: Sun, 22 Feb 2015 22:49:49 +0000
Greetings All,
I can hear the roar of delete keys already, but for the eight of you who have
followed along to this point, I'll share the link to a gallery of gull photos
that I took yesterday. All of the photos show birds in definitive adult basic
plumages. There are no mottled brown first-cycle birds, or ratty third-cycle
birds
with missing flight feathers or oddly retained feathers from prior
plumage cycles. As gulls go, this is the fairly easy stuff. All of the photos
were taken at the Port of Kalama, WA over about an hour span. I attempted to
take them from a consistent angle, so the lighting conditions remained fairly
constant. As you can see, trying to discern differences in the gray tones on
the upper wings and mantles of these birds in the relatively bright midday sun
was a fools errand.
There are five species of white-headed, similarly gray-mantled, black
wing-tipped gulls (Mew, Ring-billed, California, Thayer's and Herring) that
occur across much of Oregon during the winter months. It is fairly common to be
in situations where large mixed groups of these five species are flying by.
Field guides will point out differences in mantle shade as a useful way to
compare one to the others. However, in many lighting conditions (particularly
bright sunny days) it ranges from difficult to near impossible for most of us
to tell the difference between the back color of the lightest-mantled birds
(Herring and Ring-billed Gulls) and the darkest-backed species (California and
Mew). In the middle, we have Thayer's Gull, which most birders find confusing
on several levels.
The purpose of this photo gallery is to compare and contrast the
black-and-white wingtip patterns in the adults of five superficially similar
gull species. It works through the species from the smallest (Mew) to the
largest (Herring). After several decades of gull study, I've developed a set of
helpful clues that generally work well when I am faced with sorting through
flyby gulls streaming along a river towards a roost site, or filing past a
coastal seawatch. If this gallery of photos and the associated captions (roll
your cursor over the large selected image to view captions) help even a few of
you increase your comfort level with gulls in flight, I will consider this
effort to be a success. If nothing else it has helped me reinforce and quantify
the field marks that I've used to separate these species going back to the late
1970's.
http://www.birdfellow.com/photos/gallery/943-wingtip-patterns-of-five-similar-adult-white-headed-gulls
Dave Irons
Portland, OR
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