Hi Jill (and others now privately involved in this
debate),
Sorry, yesterdays response was shoddy and incomplete and my interpretation
of Rob Drummonds birds confused because I misinterpreted the date the
photos were taken. On the slides he wrote 04/02. I assumed this meant
4th February. I now realise he meant April 02. Rob is away until 26 January so I
was unable to check and he couldn't correct me. So the plumage of his birds is
conventional. My revised analysis is below.
Also, I didn't explain why I dismissed Roseate Tern so readily as a
possibility for your bird. In my opinion, young Roseates,
those with carpal bars, never have red on the bill.
I agree your bird is a Common Tern,
possibly of the nominate subspecies hirundo. However, because on
the breeding grounds in Siberia, there is a wide area of overlap between
the races, this is not certain. In the this area, individuals may more closely
resemble either that form or the far eastern, black
billed, longipennis. In Victoria, although typical
longipennis out number other forms, birds resembling hirundo are
not uncommon. When I was 'studying' Common Terns back in the 60's, we
reckoned we were getting two intermediate races, minussensis and
turkestanica. These have now been absorbed into the other two as there
are no clear demarcations. Thus only extreme individuals can reliably be
assigned to a subspecies. A third subspecies, tibetana from
central Asia is said to occur in HANZAB region. Plumage and size are as
longipennis whereas bill and legs are like hirundo so have
much red.
ID to race is further complicated because the
species takes three years to achieve full adult plumage, the three
ages moulting in different periods. This is very detailed in
HANZAB but unfortunately doesn't show when bare part colours
change.
The day Jill posted her query, I received a letter
with photos from Rob Drummond with a similar problem. They were terns taken
at Ricketts Point in Port Phillip Bay in April 2002. Rob was confident that a
black billed, red legged bird with black primaries, dark carpal
bar and partially black, irregular shaped, non-breeding plumaged, crown (not
extending to nape), was a Common Tern. This, I understand, was typical of others
present. His query bird had a black bill,
black (possibly tinged red) legs, white forehead but remainder
of crown to nape black, no carpal bar, grey, not black primaries and long
tail streamers extending to tip of folded wings. I consider this was an adult
Common Tern of the race longipennis in almost full breeding plumage, needing
only a black forehead, a darker belly and perhaps some moderation in colours of
bare-parts to complete the
process.
So the red-billed bird was in
1st immature non-breeding plumage (about ten months old), probably from a
population breeding in central Asia or further west whilst the black-billed bird
was an adult longipennis (at least 34 months old) which had completed
it's primary moult and was in the process of completing it's body and head
moult, exactly in accordance with HANZAB.
This makes more sense.
Mike Carter
30 Canadian Bay Road
Mt
Eliza VIC 3930
Ph: (03) 9787
7136
Email:
----- Part of Original Message -----
From: jilldening <>
To: birding-aus <>
Sent: Sunday, January 12, 2003 11:37
PM
Subject: [BIRDING-AUS] Tern, not sure which,
SEQ
Hi Everyone,
Jill Chamberlain
spotted an unusual tern in the final ten minutes of our time at the sandbanks,
after the first
load had started back to shore. At the time she came to me
and said she
thought she had a Common Tern in her scope, except it had red
legs and bill.
It was preening vigorously with its head mostly away from us.
It was partly
obscured all of the time in a flock of about a thousand or two,
and I never
saw its primaries or tail. Then the flock lifted, and we couldn't
relocate it.
For the record, this is what I did see:
Bill part bright
red, part black
Legs bright red
Very strong carpal bar
Stronger cap
that Common Terns present (which are still showing no cap
movement from
non-breeding), but not full cap
Otherwise like a Common Tern, same
size
I feel that it was most likely a Common Tern. But I think there is
the
possibility that it might be the first time I have ever seen (and
I
emphasise the MIGHT) the nominate species of Sterna hirundo. There
has been
the odd record of a nominate on the east coast, but the usual place
for
these to turn up is on the west coast of Australia.
However, they do
breed as far east as western Siberia. From east of this
point the subspecies,
our subspecies, longipennis, takes over.
I just wonder if it could just
be one of our regular longipennis with more
red that is usual. Not sure. I
have seen Commons before showing dark red
legs and dark red on bill, but this
was bright red, somewhat like the red on
the bill of a Caspian
Tern.
Cheers,
Jill
