I tend to agree with the suggestion made to me by Alan Morris in a private
email that the CBC that I observed at Ryde on 18/07 was likely to be an
over-wintering bird rather than an early arrival. Of course, there is no way
of telling if that suggestion is correct.
Stephen Ambrose
Ryde, NSW
-----Original Message-----
From:
On Behalf Of Andrew Taylor
Sent: Sunday, 23 September 2012 8:59 PM
To:
Subject: changing Channel-billed Cuckoo arrival times
Birdline New South Wales has this this afternoon:
"Except for Stephen Ambrose's July sighting all other sightings of CBCs
listed below are in accordance with the typical arrival dates of CBC in
the region. We decided not to publish any further in-season CBC sightings
(except for unusual observations). 18/07: Ryde, Stephen Ambrose (this
one was the only early one!); 31/08: Annandale, Simon Gorta; 01/09: Wangi
Wangi, Steve Roderick; 02/09: Beacon Hill, Robert Griffin; 03/09: Bateau
Bay, Alan Morris; 05/09: Bilgola Plateau, Alan McBride; 06/09: Penrith,
Akos Lumnitzer; 08/09: Castlereagh, Akos Lumnitzer; 09/09: Surry Hills,
Penny Evans; 13/09: Ulladulla, Bob Rusk; 14/09: Turramurra, Tom Wilson;
16/09: Penrith, Akos Lumnitzer; 19/09: Pymble, Margaret Hall; 19/09:
Oatlands, Tony Dawe (attached photo); 20/09: Kogarah, Harry Roberts;
22/09: Pennant Hills, Cameron Galle."
I remember when most of these observations, and my unreported observations
for the last 2 weeks in Glebe, would have notable
But Beaumont et al. [1] looked at reported first arrivals for
CBCs in Sydney 1973-2004 and first arrival was getting 3/4 of day
earlier. According to their linear regression, expected first arrival
time in 1973 was Sep 24, by 2004 it was Sep 2 and now it would be Aug 27 -
supporting the Birdline NSW moderators summary.
Beaumont et al. attribute this, with other arrival time changes, to
climate change. But for CBCs changes to host abundance particularly
Pied Currawongs and human vegetation modification look more likely to
me to be large factors,
Andrew
[1] LINDA J. BEAUMONT, IAN A. W. McALLAN, LESLEY HUGHES A matter of
timing: changes in the first date of arrival and last date of departure
of Australian migratory birds Global Change Biology Volume 12, Issue 7,
pages 1339-1354, July 2006
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