Thanks Tony and Jeff for the discussion, though I think trying to pick out a
RBG from a SG is quite a bit beyond me. Especially if the bill size and
shape varies within SG's and SG's can sometimes have 2 mirrors or 3 mirrors
on their primaries. Though I did find this interesting webpage showing a
comparison of the skulls of the 2 birds.
http://www.shearwater.nl/index.php?file=kop98.php
At least it's given me more to keep an eye out for next time. For a common
bird there is certainly lots of variety in them, like this image I took of
this adult bird with a very dark eye. http://bit.ly/jg2XeJ
I was looking through the BirdingAus archives and found this old thread from
2003 on the same subject if people are interested in reading that one too.
http://bioacoustics.cse.unsw.edu.au/archives/html/birding-aus/2003-07/msg004
28.html
Regards,
Mark
-----Original Message-----
From:
On Behalf Of Jeff Davies
Sent: Tuesday, 28 June 2011 4:51 PM
To: 'Tony Keene'; 'Birding-Aus'
Subject: Gulls and Terns in Sydney
G'day Tony,
Interested to see the photos Tony if you haven't already headed off to
Adelaide.
Three spots is the norm for adults in SE Australia however, the other
northwest half of Australia is more likely to have two window spots, it is
the norm in northern(including Darwin?) and north/west Australia. It
wouldn't be impossible to see an adult Silver in SE Aust with only two
spots. Immatures in SE Aust, including 1A, also show only two spots.
Scopulinus has a shorter bill, this would be the most obvious difference
with adults that you should look for, but if you start looking you will note
quite a lot of variation within your typical flock of Silvers.
It's the juv of scopulinus that lacks the tail band not the other way
around, this is another good feature and would hold through to 1B 1A?.
Cheers Jeff.
-----Original Message-----
From:
On Behalf Of Tony Keene
Sent: Tuesday, 28 June 2011 3:52 PM
To: Birding-Aus
Subject: Gulls and Terns in Sydney
I've done a fair bit of snooping around the literature and I'm almost
certain it was a Red-billed Gull. I'm off with work for a few days to
Adelaide and I'll get some more work done on it. When I get back, I should
be able to let everyone know what I've got and why I reckon it's an RBG.
Cheers!
Tony
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