Fwd: Thayer's Gull at Georgetown Reservoir, DC
PObrien776@aol.com
Mon, 25 Jan 1999 13:58:51 EST
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Dave Abbott asked that this be forwarded to MDOsprey.
pobrien776@aol.com
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Date: Mon, 25 Jan 1999 11:33:44 -0500
From: David Abbott <DFAbbott@compuserve.com>
Subject: Thayer's Gull at Georgetown Reservoir, DC
Sender: David Abbott <DFAbbott@compuserve.com>
To: "Paul O'Brien" <pobrien776@aol.com>
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Paul
Hi, I just returned from the reservoir and thought this might be of
interest. I don't sub. to MDOSPREY. Would you mind passing it on?
Thanks,
David Abbott
Below, I have attached the notes I have made about the Thayer's Gull seen
0900 at Georgetown Reservoir, Washington DC on 1/24/99.
All of the descriptive notes are mine made in haste at the time, the
identification is based on my experience (no references consulted, yet).
All questions and comments welcome.
THAYER'S GULL (1 first winter)
LESSER BLACK-BACKED GULL (1 2nd winter)
___________________
Approximately 0900 several hundred gulls using the reservoir, about equal
numbers of Ring-billed and Herring. Of the Herrings, most were adults
(350), followed by first winter (200) and the 3rd and 2nd winter. While
scoping swimming Herrings, I found one first winter thayeri swimming at
close range. Studied for 30 min. from all angles as well as in flight.
Pale gray-brown smithsonianus type with proportions as the LBBG which was
about 2 feet. Scaly, barred pattern across mantle to include scapulars an=
d
wing coverts. The median and greater coverts were patterned with spots on
a creamy-brown background. Scaly, barred mantle, pattern of wavy brown
bars of equal width on very pale background, inconsistent with
smithsonianus. As were the pattern of scaps. and coverts. The tertail
pattern was more solid than greater coverts, but gave way gradually to the
distinct spotting of coverts. Primaries long, P4 =AD P5 lining up with ta=
il
tip. P's dark browner than smithsonianus, with clear cream streak on inne=
r
web only, visible on all exposed P's. The head pale shadowy brown with a
slight darkening lengthwise through the eye. Loral area white, feathering
longer on upper mandible than lower. Head flatish, sloping on forehead,
with slight peak behind eye. The entire breast, belly, flanks and
undertail coverts smooth but darker gray-brown with very fine but distinct
white vermiculations. Belly and flanks darkest but not as the darker
coarser areas of smithsonianus. Undertail coverts palest with sharp brown
chevron bars beginning before tail and becoming stronger and broader
rearward. Tail choc. brown, white outer web on each side (brown notched)
and narrow white terminal band. Tail darker than P's, without pattern.
Rump and uppertail coverts brown and white barred, the latter overlapping
tail base giving impression of tail band. Flight feathers from below
ghostly-gray or silvery-gray with the darkest area of underwing being the
linings. The pale bases to the greater coverts and P coverts, having brow=
n
tips, formed a ring around the linings. Tail pale and unmarked from below=
,
the barred undertail coverts distinctly obvious.
On the upperwing, secondaries same color as innerwing but formed a series
of brown longitudinal stripes (not band or bar). The P's were similar but
palest on inners (P6 =AD P10), the outer five to six primaries brown on ou=
ter
webs only. Each P brown to tip with a narrow fleck on the inner web,
forming characteristic 'L' pattern. Bill solid black, culmen curve steep
and beginning past mid-point. Bill depth shallow, slight pinch at base.
Identification: thayeri is justified by combination of structure, wing
covert pattern, tail and uppertail covert pattern, and the 'L' pattern to
P's.
Best,
DFA
dfabbott@compuserve.com
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