I was told this is a posture related to mating behavior.
Nearest potential same-species mate is a few thousand miles away.
Explains the name!
Not a great photo but the only one I got showing upper wing.
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The location where the bird was seen all day on 9/7/17 (Swallow-tailed Gull is in there somewhere).
It never moved off that rock in the eight hours I was there!
The south end of the Edmonds Marina Public Pier
There were quite a few more birders at various times during the day.