Glaucous Gull, Washington DC, 15 FEB
2004
This basic II -alternate II bird was
observed at length with Rob Hilton, Paul Pisano and Lisa Shannon. It seemed
remarkably small. In some poses it appeared to be smaller than some smithsonianus,
although always seeming more angular in build. It always lost its battles over
fish, even with first year Herrings, and then adopted a very submissive posture.
Glaucous Gulls from northeastern North America are L. h. hyperboreus, or
sometimes treated as L. h. leucerectes. While hyerboreus averages
larger than smithsonianus, female hyperboreus show substantial
overlap with male smithsonianus in wing, bill length, and tarsus.
A further twist appears in the first
thumbnail below (wing-shot). In this, and only this wing photo, the light and
angle is just right, and you can see a very faint, symmetrical pattern of
brownish gray on BOTH webs of P10-8. The pattern looks almost adult-like, with
mirrors and sub-terminal darker spots. Olsen and Larsson, in Gulls of Europe,
Asia and North America, p.194 state (under the description of barrovianus)
that a "small minority show faint dark wash to outer webs of
P8-10." It would be nice to see barrovianus skins or photos.
It would also be nice to see this bird as a full adult. Perhaps those faint
markings will go away. Olsen and Larsson, p.194, mention (under Aberrant) adult
Glaucous (not barrovianus?) with dark marks on P10-9 and speculate that
this is "the darkest variant or hybrid (probably with Herring Gull.)"
This suggests there is a chance the DC bird is a backcrossed Nelson's Gull. A
photo of an interesting bird along these lines (but it has a darker mantle)
appears in Birding World 10, p.275. The primary markings on the DC bird are very
faint, and perhaps lack significance, but they make me wonder about the bird's
ancestry.
