When Duncan sent me the first photos of these terns taken at Marlay Point,
Lake Wellington, near Sale, Victoria, on 12th August 07, see
http://www.natureofgippsland.org/coppermine/thumbnails.php?album=38&page=1,
I thought the larger bird (apart from the obvious Crested Tern of course)
possibly a Common Tern and the smaller an Arctic Tern but wasn't certain.
Two other very experienced observers expressed similar opinions and I
learned that two terns seen distantly on 25 July at this spot were claimed
as Common Tern by another erstwhile reliable observer. Common Terns are
common in summer from October to April in the Gippsland Lakes but a winter
record would be very unusual. So I had that species very much on my mind.
Next day I joined Duncan and his friend Peter at the site. We saw up to six
of the smaller terns together, possibly 8 in total, in addition to ~ 50
Crested Terns. The habitat is basically an inland sea, until recent floods a
saline lake. The birds disappeared to the lake centre to feed with the
Crested Terns. All around were fresh water lagoons, remnants of the recent
floods. These were ignored.
I was absolutely flummoxed by them! Totally bewildered! Must be past it!
Duncan demanded an ID because anticipating my visit, he'd promised to advise
the public on his web site. But I couldn't provide it!
All the birds I saw had wholly black bills and bright red legs, more orange
in a juvenile. In spite of numerous differences, there was sufficient
consistency for me to believe that just one species was present! Some adults
had dark blotches on underparts (remnants I mistakenly thought of breeding
plumage of longipennis Common Tern or Arctic Tern). Features in favour of
Common Tern included leg length and grey rump and tail. Features in favour
of Arctic were tonsured head pattern of some and that no birds had the black
wedge on the outer upper wing formed by old outer primaries expected in
Common Tern at this season. Underwing pattern was somewhat ambivalent but
more inclined to suggest Common than Arctic.
The juvenile was particularly perplexing. I had not previously seen as young
a bird at this time in Australia! It was beyond contemplation that a
juvenile could have arrived so early in Australia having flown from the
northern hemisphere. But it did provide one answer. I could rule out Arctic
Tern because in juveniles of that species the secondaries are unmarked
wholly white. In this bird each feather had a dark centre. But neither were
they Common Terns! So I called for help and emailed Chris Corben and Danny
Rogers. Both responded immediately politely hiding their disdain but really
saying you stupid old fool, they're WHISKERED TERNS. With the blinkers now
off, it was all perfectly clear. Well almost. Whiskered Terns are very rare
but not unknown in winter in Victoria, it was an early date for returning
migrants and usually when they do arrive, they are in breeding not
non-breeding plumage.
The first of two remaining problems was what was a juvenile doing here in
August? Where had it come from? Any bird reared locally, even say a very
late breeder born in February should by now be in first winter non-breeding
(first basic) plumage. Moult into that plumage is completed within 2-3
months of fledging. So that bird was less than 3 months old, probably two
months or less. So I surmised that it had been bred in northern Australia or
perhaps Indonesia. Checking HANZAB I read that all breeding records were
south of 25 degrees S in spring/summer (but now can't find those words!).
However, since HANZAB was written there has been a breeding event on Anna
Plains near the Sandfire Roadhouse in northern WA in autumn. This has led to
speculation that some individuals may breed twice in one year, once in the
south then again in the north! This would be in accordance with its normal
behaviour of opportunistic breeding and its apparently inexplicable erratic
moult sequences.
The other problem was the apparent size difference between the first two
birds. Some say that is illusion but I think it's real. The larger bird is
also darker. Could the larger, darker bird be of the northern hemisphere
subspecies Chlidonias hybridus hybridus and the smaller paler individual C.
h. javanicus, the normal Australian subspecies? These are the characters
that separate these races. The northern form is known to reach the Greater
Sundas so why not Australia?
Jeff Davies also took many photographs at this site on Sunday 19th August
and also saw one Little Tern in non-breeding plumage. Again an early date I
would think. Next day Duncan had several Little Terns there. At first glance
I'd suggest they're Asian birds rather than Australian breeders.
Mike Carter
30 Canadian Bay Road
Mount Eliza VIC 3930
Tel (03) 9787 7136
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