G'day Nikolas,
This is the third time you have posted this so I guess your looking for a
response. So here's mine, firstly Michiaki called it a Slaty-back last
Friday so he should get my golden gong award for calling it first, but I
don't think he's particularly concerned about that sort of stuff. Anyhow
since last Friday we have all collectively been working through all possible
species ruling them out to see what's left, no matter how confident
particular people are about the ID this is surely correct procedure. As you
have pointed out a lot of potentials were ruled out quickly early on to a
point where only vegae, smithsoniensis and schistisagus were left, then the
primary projection aspect was tossed in and it quite possibly left
Slaty-back as a last man( or in this case woman ) left standing. No species
is a best fit with this bird but as Michiaki correctly pointed out last
Friday scapulars are the only thing less typical for Slaty-back with this
bird. I have now seen plenty of images of 1st basic Slaty-backs thanks to
Michiaki's website showing anchor marked scapulars like the Cooktown bird to
know that while it's not typical it does never the less occur for a
percentage of individuals. To consider this bird as one of the other
possibles you have to contend with a much larger number of features
considered less typical aside from the primary projection issue. To this
point I cannot find a single image of one of the other possibles showing all
of the less typical features together in one bird like the Cooktown bird,
but there are a number for Slaty-back images around showing the one
divergent feature relating to Scapular pattern.
I think we are all happy to keep the discussion going if there are more
things to consider so can you outline the issues still unresolved as you see
them. Do you want to discuss the primary window for example, I personally
can't see a problem with it.
Cheers Jeff.
-----Original Message-----
From:
On Behalf Of Nikolas Haass
Sent: Saturday, 23 February 2008 3:34 PM
To: Tony Russell; Mike Carter; BIRDING-AUS
Subject: Cooktown Slaty-backed Gull happily post
sittingtoday
Although I was the first one who dared to ID the bird as a female
first-winter Slaty-backed Gull (see old posting below), I still would NOT
say that we 'SETTLED' on a definite ID.
We clearly ruled out Thayer's Gull, American Herring Gull (see below), the
fuscus complex including Heuglin's Gull (heuglini and taimyrensis), Eurasian
Herring Gull, and most of the "yellow-legged gull complex". Moreover, as I
indicated a week ago, tail and primary patterns speak against Mongolian and
Steppe Gull.
And also Vega doesn't fit 100%. But - although it was my favorite - does
Slaty-back fit 100%? No, it looks good for a Slaty-back, but apparently not
100%! Look at all the divergent comments from experts from all over the
world! I think, the final ID at this point should be "possible Slaty-back".
Two years ago, two friends of mine (Eric Pilotte and Simon Thompson) and I
found two interesting subadult gulls in Barrow, Alaska. We nailed them down
to Heuglin's Gull (heuglini or taimyrensis) but were never able to 100% rule
out Lesser Black-backed Gull - so we decided to call them possible Heuglin's
Gulls. (of course, we had plenty of Vega and Slaty-backs there...)
Cheers,
Nikolas
Here my posting from a week ago:
Jon, Mike, Richard et al.,
Yesterday when I saw the first two pictures of the perched gull my "gut
feeling" immediately ruled out Thayer's and I indeed thought of Vega Gull,
barabensis-Steppe Gull, mongolicus-Steppe Gull or Slaty-backed Gull.
Now I've seen Richard Baxter's flight shots. The large pale window in the
primaries indeed immediately rules out the fuscus complex including
Heuglin's Gull (heuglini and taimyrensis), but it is in my opinion also way
too large for so-called "Herring Gull Complex" (Eurasian Herring Gull,
American Herring Gull and Vega Gull) and for the "Yellow-legged Gull group",
including mongolicus and barabensis. The pale window (formed by the pale
inner webs of the primaries vs. dark blackish brown outer webs and tips) in
the Cooktown bird actually reaches P9!
The pattern of the primaries (which looks good for Slaty-backed, but also
for Thayer's), the spotted/barred upper and under tail coverts with broader
white than dark bars (looks better for Slaty-backed Gull than for Thayer's
and also rules out American Herring Gull), the almost solid dark blackish
brown tail (which speaks against Eurasian Herring Gull and the
"Yellow-legged Gull complex", but also against Vega Gull), the bleached
scapulars (which in my opinion don't necessarily rule out a first-winter
Slaty-backed Gull), and the bill shape with a relatively flat gonydeal angle
(which would rule out a male Slaty-backed Gull) makes me think of a female
first winter Slaty-backed Gull.
I am looking forward to more comments that hopefully will finally lead to a
positive ID of this interesting bird!
Nikolas
and another one:
However, typically first-cycle American HG appear very dark: the underparts
of a first-cycle American HG are typically uniformly brown and not as
splotchy as in the Cooktown bird. Also the upperparts are typically darker
due to narrower pale fringes of mantle feathers and scapulars. The most
important field mark are the under tail coverts which are densely barred
with the dark proportion of ore than 50% leading to the impression of dark
brown undertail coverts with very narrow white barring (and not white
undertail coverts with some brown spotches and bars as in the Cooktown
bird). This pattern is somewhat reminiscent on that of a juvenile Pomarine
Skua! Similar 'rules' apply for the upper tail coverts. The tail of a
first-cycle American HG should typically be totally dark brownish black, but
there are many birds
with barring at the bases of the outer three rectrices. Another interesting
fact is that typicalley American Herring Gulls still have juv. mantle
feathers and scaps in February.
Cheers,
Nikolas
P.S. Two friends of mine (Martin Gottschling and Andreas Buchheim) and I
just had a paper (unfortunately in German) accepted for publication in
Limicola. I spent the last five years in the US and documented a lot of
American Herring Gulls of various populations, whereas my friends did the
same in Europe with European Herring Gulls.
----------------
Nikolas Haass
Sydney, NSW
----- Original Message ----
From: Tony Russell <>
To: Mike Carter <>; BIRDING-AUS
<>
Sent: Saturday, February 23, 2008 2:29:38 PM
Subject: Cooktown Slaty-backed Gull happily post sitting
today
So, have we settled on Slaty-backed now ? Going Tuesday.
-----Original Message-----
From:
On Behalf Of Mike Carter
Sent: Saturday, February 23, 2008 10:45 AM
To: BIRDING-AUS
Subject: Cooktown Slaty-backed Gull happily post sitting
today
The floods have subsided, fine weather has returned to Cooktown and the
Slaty-backed Gull is extant on her post. Colin Judkins took 3 hours 40
minutes to drive there from Cairns this morning.
Notice David (Taylor), it is a 'she' not a 'he'!
Mike Carter
30 Canadian Bay Road
Mount Eliza VIC 3930
Tel (03) 9787 7136
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