Cooktown Gull discussion

["Lisa Hug" <>]

Hi Australian Birders,

Chris Corben has been sending me photos and correspondences about the Cooktown 
Gull.

I have been following it with great interest.

I really think that the Herring Gull and American Herring Gull complex may
have been dismissed too easily on the basis of primary pattern and tial
covert patterns.

Even though there are pale inner webs to the outer primaries - even out to
9,  there is still a pronounced difference in the amount of pale webbing
form the inner primaries and the outer primaries.  There is a sharp boundary
between P4 and P5, giving it a nice windowed appearance.  In the flight
photo on Tony's web page, the pale webs to the inner primaries are barely
detectable as they are concealed behind other primaries.  The shot the Keith
and Lindsay got with it's wings spread on the post, showed extensive paleness 
in the primaries because the wings
were very stretched - exposing the webs right out to P9.  I believe if one
takes a Herring Gull's wing and stretches it as far as they can, they will
find all of the inner webs are pale - just less extensively on P5-10 than
P1-4.  I believe the same is true with the secondary pattern as well.

I am also not convinced that the tail covert patterns eliminates Herring
Gulls.  Olssen and Larssen describe Mongolian Gull as having a white rump
and tail-coverts, sometimes with dark spots, especially along the sides.

Herring Gulls have variable amounts of black and white on the tail coverts
and rump.

The Cooktown bird's rump and uppertail coverts appear to be splotched half
and half pale and dark.

It's hard getting around that dark tail.   There are definitely flecks of
white in the basal third of the rectrices.  But, I would not call that barred.

The tail pattern fits American Herring Gull (Smith) extremely well.  In fact, 
the darkness of the tail is a blessing because it makes the bird less likely to 
be in the the Larus argentatus comples and more likely to be a Larus 
smithsonianus.   I do not know about the variation in the tail patterns of 
European Herring Gull, but I know the Cooktown bird fits a Smithsonian pattern 
very well.

Other features that fit well.

Howell and Dunn's book describe the tail as ending between the 6th and 7th
primary of the closed wing on Smithsonian.  That is the case with the Cooktown
bird.  I do not know, however, where the end of the tail would fall on a
Mongolian Gull.

The Cooktown bird has very dark tertails. This fits better with Smith than
Mongolian.

I was in the field yesterday and found a nice first cycle American Herring Gull 
on a central California Beach.

I was with a very good photographer Ruth Dundas and she got the attached photos.

Notice that there are pale webs to the outer primaries and secondaries.  The 
tail is also very dark with some pale flecking at the base.


Sincerely,

Lisa Hug

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