[Tweeters] Fwd: [obol] Re: Possible BLACK-TAILED GULL at McNary Dam
jdanzenbaker at gmail.com
Sun Jan 4 22:35:44 PST 2015
---------- Forwarded message ----------
From: David Irons <llsdirons at msn.com>
Date: Sun, Jan 4, 2015 at 10:32 PM
Subject: [obol] Re: Possible BLACK-TAILED GULL at McNary Dam -- ISN'T
To: Alan Contreras <acontrer56 at gmail.com>, Craig Miller <gismiller at gmail.com>,
OBOL Oregon Birders Online <obol at freelists.org>, Scott Carpenter <
slcarpenter at gmail.com>
Cc: Stuart Johnston <johnstonstuartf at hotmail.com>
I want to close the book on the McNary bird and also offer a quick comment
on Craig Miller's response posting about a larger gull with significant
black in the tail (seen near John Day Dam).
Regarding Craig's bird -- As Alan Contreras indicates, Black-tailed Gull is
smaller bird than what Craig describes and it has a complete subterminal
black band in later plumage cycles. It also has a terminal white band that
is fairly wide, much wider than the subterminal black bands that we see on
many second-cycle N.A. gulls. I would surmise that Craig's bird was a
sub-adult Glaucous-winged X Western hybrid (perhaps post F1). "Olympic"
Gulls show all sorts of anomalous characteristics that don't seem to equate
to apparent age (based on the rest of the plumage or bill pattern).
Since getting back to Portland, Shawneen and I have reviewed the rather
substandard, but still useful photos that I took of the "black-tailed gull"
(note lack of capital letters). Aside from the rather conspicuous solid
black subterminal band on the tail, this bird shows characteristics that
are dead on for a third-cycle (not definitive adult) California Gull. In
addition to reviewing my own photos, I looked at some photos that Scott
Carpenter took while we were still in the field. He has a BIG lens, thus he
got better photos than I did.
When looking at his images, two things were clear:
1. This bird is *not* an adult. When I looked at Scott's photos I could see
that there was black in the primary coverts and on the two outermost alula
feathers if I am remembering correctly. I also noted the black on this part
of the wing when the bird was flying directly towards us at one point.
Fully adult white-headed gulls (Mew Gull on up in size) don't show black in
primary coverts or on the alula feathers. The black in the wing is
restricted to the primary tips in adults of this group of gulls.
2. There are subterminal white windows in both Primary #10 (P10) and P9.
The one in P10 is fairly long and the one in P9 is shorter and less
obvious. My photos show the same thing. The position and extent of the
white in these two outermost primaries is a near perfect match when
compared to flight photos of similar-aged California Gulls. I can't find
any photo of a later cycle (after second-cycle) Black-tailed Gull that
shows a white subterminal window in either of these feathers.
My poorer quality images show that the terminal white on the tail feathers
is rather narrow and not wide enough for a Black-tailed Gull. In flight at
closer range (second viewing of the bird in flight), neither Shawneen nor I
thought that the bird looked long-winged enough or long-billed enough to be
a Black-tailed. Further, it did not seem nearly dark enough on the mantle.
Black-tailed Gull should show a slightly darker mantle than the darkest
California Gulls. This has been a great exercise that reinforces the
reality that one conspicuous (apparent) field mark–in this case a broad
black tail band on a bird that appeared to be a full adult, or nearly
so–does not a rare gull make. Whenever looking at a bird that seems to
possess a tell-tail field mark (pun intended), it is important make sure
that other corroborating field marks are seen. In this case there were none.
It is a long drive from where most of us live to chase this gull (unless of
course you would like to see a Black-headed Gull) and I want to make sure
that no one makes this trip in hopes that this bird might prove to be a
Black-tailed Gull. It will not! This species has occurred in Washington
several times and remains one of the most overdue birds for Oregon.
Thankfully, both Shawneen and I have previously seen Black-tailed Gull(s)
so we both noticed that several aspects of the bird did not seem "right"
once we saw it fairly close up. Our initial views of it were in flight at a
distance of at least a quarter of a mile then it landed on the concrete
wall below the dam on the Washington side of the river (roughly a half mile
away). Shawneen picked out as it sat on the wall when she saw the tail
extending out from behind another gull that was standing in front of it.
These views were tantalizing, but far from conclusive. Fortunately, the
bird got up and flew around, eventually coming to within about 80-100 yds
of the Oregon shore.
Scott -- I know that you are on Tweeters (neither Shawneen nor I are
subscribed). Can you or someone else who subscribes please forward this to
Tweeters so that the Washington folks know the story. There were a number
of Washington birders who saw this bird with us and some may still be
thinking that it's a Black-tailed Gull.
Battle Ground, WA
jdanzenbaker at gmail.com
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