Nikolas, Mike, Jeff et al,
I feel I should reply as the initial "devil's advocate" for the possibility of
the bird being a hybrid. I would first of all like to point out that I never
suggested that the bird was actually a hybrid, but from an "outsider's"
perspective (ie not being involved with the rigorous ID exercise and certainly
not pretending to be), I just proposed the possibility basically to see if
people (especially those with expert knowledge) agreed that this bird could
actually be positively identified.
According to the majority of sources now, it appears that an ID has been
settled. But as Nikolas has asked here, has the possibility of it being a
hybrid been ruled out? Surely this would need to occur before anyone can be
certain of what it actually is. There appears to be much debate on many
"difficult to identify" Gulls and this is the main reason why I threw this into
the frey.
To put the advocate's hat on again (just for the sake of it), I have wondered
about similar ID problems for certain species such as the Diving Petrels. When
we look at these birds on a pelagic trip off Tasmanina, for example, obviously
all or the vast majority of them are going to be Common DP's...but until we
have the bird in the hand, how can we be certain that what we are looking at
are not South Georgian DP's?
Is a "positive ID" always such?
Just ID food for thought.
Mick Roderick
----- Original Message ----
From: Nikolas Haass <>
To: Mike Carter <>; Tony Russell <>;
BIRDING-AUS <>
Sent: Saturday, 23 February, 2008 7:05:53 PM
Subject: Re: [Birding-Aus] Cooktown Slaty-backed Gull happily post sitting today
Hi Mike and Jeff,
What I wanted to say with my provocative mail is that we obviously had problems
ID'ing this bird. For me it still could very well be a Slaty-back and I also
pointed out earlier that I don't like to call everything a hybrid that I can't
ID - but did we really rule out a hybrid? I do agree that many features speak
for Slaty-back and that's why I initially ID'd it as such. However, several
others vehemently ruled out Slaty-back (because of color and pattern of scaps
and mantle feathers, because of the size and shape of the bill and I think
there were more mentioned). So apparently it is not a 'straight-forward' ID. So
after all this confusing back and forth, I really would be curious about the
results of a DNA analysis!
Nikolas
----------------
Nikolas Haass
Sydney, NSW
----- Original Message ----
From: Mike Carter <>
To: Nikolas Haass <>; Tony Russell <>;
BIRDING-AUS <>
Sent: Saturday, February 23, 2008 6:08:40 PM
Subject: Re: [Birding-Aus] Cooktown Slaty-backed Gull happily post sitting today
Nikolas Haass <> said today
To: "Tony Russell" <>; "Mike Carter"
<>; "BIRDING-AUS" <>
> 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".
>
> Nikolas
So although you named it several days ago, you are still not 100% convinced?
Please tell us what you consider unsatisfactory in that ID.
Jeff Davies and I will prepare the BARC submission and we are confident that
we can totally justify that diagnosis. Among significant aspects that you
didn't address were the plain dark underwing pattern and short primary
projection beyond tail. Once those two features fell into place for
Slaty-backed ruling out Vega Gull the one remaining stumbling block was the
scapular pattern which was more typical of Vega Gull. But now we know some
Slaty-backs can be similarly patterned there are no contra-indications. The
presence of that second generation secondary feather noted by Alvaro was a
bonus. All discriminators are in favour of Slaty-backed Gull. QED.
Mike Carter
30 Canadian Bay Road
Mount Eliza VIC 3930
Tel (03) 9787 7136
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