The abundance diagram in Philip’s book shows you might see
3 times as many curras in Canberra gardens June-July as Oct-Feb, the
transitional periods being March-April and Aug-Sept. The seasonal maps in
the COG atlas indicate that the movement is altitudinal . Ian Rowley’s
piece in ‘Birds in the Australian High Country’ (1969) says . “
... breeds in forest country but in the autumn and winter is nomadic forming
large flocks. This movement is largely an altitudinal shift and large
flocks appear in towns on the highlands during winter”.
HANZAB says: “In Canberra, numbers increase with
influx of visitors, said to be from surrounding ranges, in mid-Mar., with
maximum numbers in May-June, and most depart in Sept., after which only
breeding birds remain ...”
As I think Michael has pointed out at COG meetings, the pattern
might have changed somewhat. McComas Taylor (1992) said “Until the
1960s, the outward movement was almost complete, and very few bred in Canberra
[Rowley], but in recent decades they have acquired new patterns of behaviour
and have learned to exploit rich food sources available during the breeding season
at low altitudes ...”
I wonder if the last few years have not seen a further shift in that
direction. The density of nests in Canberra seems very high, with fairly
small and virtually contiguous territories, and some double-brooding. The
success rate must also be quite high. So what happens to the young of the
year? Do they join up with the transient flocks and summer in the hills,
contributing to ever-larger flocks? I think the theory that there are not
more currawongs overall needs a close look. The long-term line in Philip’s
book is flattish but that might indicate maximum density has been reached in
garden sites. It is one of the ‘increasers’ in the second BA
atlas. g
From: Michael & Janette Lenz
[
Sent: Sunday, 16 March 2008 7:44 AM
To: chat line
Subject: [canberrabirds] currawongs
I
remember being told that the overall numbers of currawongs in Canberra had NOT
increased much over time, however, the birds now spent the whole year here
rather than being seasonal. That means that the poor little birds have now less
and less of a chance to survive the predation.
But
I have forgotten whether it was that the currawongs used to spend the summer
here and over-winter in the mountains somewhere, or if it was the other way
around. Can anyone tell me please?
