Hi Everyone,
Having watched Common Terns for some years, I am now teaching myself to
age them in the field, using plumage features. I am building up a
portfolio of photos of the distinctive plumages from month to month.
This has led me to a rather interesting observation, suggesting that
perhaps immatures segregate themselves from adults at certain times and
at certain places.
In early March I spent a week at Brunswick Heads in northern NSW. My
regular patch is the Sunshine Coast, Queensland, about 2-3 hrs drive to
the north. Down in Brunswick Heads I was puzzled to find that almost
every Common Tern I photographed was an immature. On the last day I saw
a few adults, as if they had just arrived. At around the same time, a
British birder was visiting his daughter at Ballina, also in northern
NSW but further south of Brunswick, and made the same observation. At
the time he assumed that the immatures would stay there for the coming
months. I told him I doubted that very much.
Yesterday I was conducting shorebird and tern surveys in the Noosa
estuary on the northern end of the Sunshine Coast. In a flock of about
1000 Common Terns, I couldn't see a single immature bird, nor did my
200 photos turn up any immatures. All were adults acquiring breeding
plumage prior to their northern migration in the coming weeks.
I am starting to wonder if the immatures segregate themselves prior to
migration. A few Commons hang around Moreton Bay during the winter, but
not anything like the numbers of immatures we see during the summer (to
my knowledge). I don't think we know where the immatures spend the
northern summer. I have been told that the nominate species (Sterna
hirundo) immatures stay behind in Africa and don't migrate to
Europe with the adults, but we don't know what happens with our
subspecies (longipennis) in the East Asian-Australasian Flyway.
Or do we? Does anyone have any information to add to this puzzle? I
don't know what happens in northern NSW during our winter. Could the
immatures stay there? Are they seen there during the winter?
Cheers,
Jill
--
Jill Dening
Sunshine Coast, Queensland, Australia
26° 51' 41"S 152° 56' 00"E
|
===============================
www.birding-aus.org
birding-aus.blogspot.com
To unsubscribe from this mailing list,
send the message:
unsubscribe
(in the body of the message, with no Subject line)
to:
===============================
|
