Hi All,
Have been following the Silver gull discussion with some interest. It seems
that while birds with yellow bare parts are not unheard of, photographs by
Vin http://yallara.cs.rmit.edu.au/~vhl/unidentified.html and Frank
http://members.iinet.net.au/~foconnor/birds/species/silver_gull.htm show
extremes that are rarely seen.
On the small gull front there are a few other interesting things in our
region worth mentioning. After a bit of prompting from Brent I had a look
the photograph taken in NZ that he had posted.
http://www.wrybill-tours.com/idproblems/strangerbgull.htm He had already
realized by the time I got back to him but I think the bird is a
Black-billed Gull (a NZ endemic), in its second year because of bill and eye
colour, not a Red-billed (NZ Silver) Gull. Brent tells me the page has had
about 50 hits since his posting yet very few people appear to have picked
this up. Characters that I think make it a black-billed are 1) its bill is
reasonably fine and long 2) the white on the leading edge of the closed wing
seems to extend too far down the wing for a red-billed gull, 3) the wings
are reasonably fine and long giving a more streamlined appearance and long
projection beyond the tail. The bird is also with other black-billed gulls
which provide a nice comparison. Given Canadian Geese, Paradise Shelduck,
Mallard (a banded bird), South Island Pied Oystercatcher and a few other
species have crossed the Tasman against the predominant weather systems it's
quite possible this species could turn up in Australia (especially on the
east coast). As Brent pointed out it's perhaps ironic that several northern
hemisphere gulls have been mentioned in the discussion but a regionally
endemic species didn't get a mention. When looking at strange silver gulls
in Australia don't forget the possibility that it could be a black-billed
gull (even if it's bill is not black). Oh and phone me when you find one :)
The other thing worth mentioning are some of the differences between NZ
Red-billed Gulls (currently Larus [novaehollandie] scapulinus) and
Australian Silver gulls (Larus novaehollandie novaehollandie). There seems
to be some overlap but the differences can be summarised as generally:
Red-billed gulls have shorter, deeper bills, the eighth primary (3rd in from
the leading edge) invariably lacks the small white mirror (not the white
tips rather the white panel in the primaries 8-10 that's about a quater of
the way up the primary), the grey dorsum is darker (after looking at a
red-billed gull recently I was struck by just how 'silver' silver gulls are)
and finally young red-billed gulls lack the dark sub-terminal tail band that
silver gulls of a similar age display.
While on Macquarie Island (sub-antarctic Australian territory) over summer
I, along with others including Gil Langfield, recorded what we initially
thought was a Silver Gull. Fortunately it hung around for a few weeks
allowing plenty of time to study it. By the time I left the island a month
later I was convinced it was a Red-billed Gull (which on geographic grounds
is more likely anyway) for most of the reasons outlined above (the fact that
it was a young bird helped). As far as I know this would be the first record
of this form for an Aust. territory. I'll have to submit it to the Birds
Australia Rarities Committee when I find the time. To this end I'd be keen
to know if anyone records gulls in Australia that appear to match the
description of Red-billed Gulls rather than Silver Gulls.
Rohan
Rohan Clarke
Zoology Department
La Trobe University
Bundoora 3086
Ph: 03 9479 1672
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