This presumed first-basic Thayer's Gull
(Larus thayeri) was photographed by Brian Gibbons; at Trinity Oaks Landfill, South Dallas,
Texas, on 16 February, 1999. Unusually, the primaries and tertials
seem to be the same pale warm brown in tone and shade; there is
normally some contrast between the pale tertials and darker primaries.
On further study I see some other unusual features: the outer
greater secondary coverts are very plain-looking (on open wing);
the solidly-dark lateral lower scapulars (visible on the 2nd image)
look like retained juvenal feathers; the uppertail appears to
be uniformly dark even at the base of the outer retrices - this
is normally a strong indicator of Glaucous-winged Gull; any
comments?:
Note how the secondaries look concolorous with the rest of the
inner wing in the upper photo, but in the picture below they look
noticeably darker - a lesson on how angle can change percieved
contrast:
